Update FLAC to 1.3.1

src/libFLAC/metadata_iterators.c

+/* libFLAC - Free Lossless Audio Codec library
+ * Copyright (C) 2001-2009  Josh Coalson
+ * Copyright (C) 2011-2014  Xiph.Org Foundation
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the Xiph.org Foundation nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+
+#include <sys/stat.h> /* for stat(), maybe chmod() */
+
+#include "private/metadata.h"
+
+#include "FLAC/assert.h"
+#include "FLAC/stream_decoder.h"
+#include "share/alloc.h"
+#include "share/compat.h"
+#include "share/macros.h"
+#include "share/safe_str.h"
+#include "private/macros.h"
+#include "private/memory.h"
+
+/* Alias the first (in share/alloc.h) to the second (in src/libFLAC/memory.c). */
+#define safe_malloc_mul_2op_ safe_malloc_mul_2op_p
+
+/****************************************************************************
+ *
+ * Local function declarations
+ *
+ ***************************************************************************/
+
+static void pack_uint32_(FLAC__uint32 val, FLAC__byte *b, unsigned bytes);
+static void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte *b, unsigned bytes);
+static void pack_uint64_(FLAC__uint64 val, FLAC__byte *b, unsigned bytes);
+static FLAC__uint32 unpack_uint32_(FLAC__byte *b, unsigned bytes);
+static FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte *b, unsigned bytes);
+static FLAC__uint64 unpack_uint64_(FLAC__byte *b, unsigned bytes);
+
+static FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator *iterator);
+static FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block);
+static FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool *is_last, FLAC__MetadataType *type, unsigned *length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata *block);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo *block);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding *block, unsigned block_length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application *block, unsigned block_length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable *block, unsigned block_length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, unsigned max_length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_VorbisComment *block, unsigned block_length);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track *track);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet *block);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture *block);
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown *block, unsigned block_length);
+
+static FLAC__bool write_metadata_block_header_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block);
+static FLAC__bool write_metadata_block_data_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block);
+static FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block);
+static FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block);
+static FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo *block);
+static FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding *block, unsigned block_length);
+static FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application *block, unsigned block_length);
+static FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable *block);
+static FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment *block);
+static FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet *block);
+static FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture *block);
+static FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown *block, unsigned block_length);
+
+static FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator *iterator, const FLAC__StreamMetadata *block);
+static FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, unsigned padding_length, FLAC__bool padding_is_last);
+static FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool append);
+
+static void simple_iterator_push_(FLAC__Metadata_SimpleIterator *iterator);
+static FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator *iterator);
+
+static unsigned seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb);
+static unsigned seek_to_first_metadata_block_(FILE *f);
+
+static FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, FLAC__bool append);
+static FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, int fixup_is_last_code, FLAC__off_t fixup_is_last_flag_offset, FLAC__bool backup);
+
+static FLAC__bool copy_n_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status);
+static FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status);
+static FLAC__bool copy_remaining_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__Metadata_SimpleIteratorStatus *status);
+static FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus *status);
+
+static FLAC__bool open_tempfile_(const char *filename, const char *tempfile_path_prefix, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status);
+static FLAC__bool transport_tempfile_(const char *filename, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status);
+static void cleanup_tempfile_(FILE **tempfile, char **tempfilename);
+
+static FLAC__bool get_file_stats_(const char *filename, struct flac_stat_s *stats);
+static void set_file_stats_(const char *filename, struct flac_stat_s *stats);
+
+static int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence);
+static FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle);
+
+static FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status);
+
+
+#ifdef FLAC__VALGRIND_TESTING
+static size_t local__fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
+{
+        size_t ret = fwrite(ptr, size, nmemb, stream);
+        if(!ferror(stream))
+                fflush(stream);
+        return ret;
+}
+#else
+#define local__fwrite fwrite
+#endif
+
+/****************************************************************************
+ *
+ * Level 0 implementation
+ *
+ ***************************************************************************/
+
+static FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data);
+static void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data);
+static void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data);
+
+typedef struct {
+        FLAC__bool got_error;
+        FLAC__StreamMetadata *object;
+} level0_client_data;
+
+static FLAC__StreamMetadata *get_one_metadata_block_(const char *filename, FLAC__MetadataType type)
+{
+        level0_client_data cd;
+        FLAC__StreamDecoder *decoder;
+
+        FLAC__ASSERT(0 != filename);
+
+        cd.got_error = false;
+        cd.object = 0;
+
+        decoder = FLAC__stream_decoder_new();
+
+        if(0 == decoder)
+                return 0;
+
+        FLAC__stream_decoder_set_md5_checking(decoder, false);
+        FLAC__stream_decoder_set_metadata_ignore_all(decoder);
+        FLAC__stream_decoder_set_metadata_respond(decoder, type);
+
+        if(FLAC__stream_decoder_init_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &cd) != FLAC__STREAM_DECODER_INIT_STATUS_OK || cd.got_error) {
+                (void)FLAC__stream_decoder_finish(decoder);
+                FLAC__stream_decoder_delete(decoder);
+                return 0;
+        }
+
+        if(!FLAC__stream_decoder_process_until_end_of_metadata(decoder) || cd.got_error) {
+                (void)FLAC__stream_decoder_finish(decoder);
+                FLAC__stream_decoder_delete(decoder);
+                if(0 != cd.object)
+                        FLAC__metadata_object_delete(cd.object);
+                return 0;
+        }
+
+        (void)FLAC__stream_decoder_finish(decoder);
+        FLAC__stream_decoder_delete(decoder);
+
+        return cd.object;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_get_streaminfo(const char *filename, FLAC__StreamMetadata *streaminfo)
+{
+        FLAC__StreamMetadata *object;
+
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != streaminfo);
+
+        object = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_STREAMINFO);
+
+        if (object) {
+                /* can just copy the contents since STREAMINFO has no internal structure */
+                *streaminfo = *object;
+                FLAC__metadata_object_delete(object);
+                return true;
+        }
+        else {
+                return false;
+        }
+}
+
+FLAC_API FLAC__bool FLAC__metadata_get_tags(const char *filename, FLAC__StreamMetadata **tags)
+{
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != tags);
+
+        *tags = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_VORBIS_COMMENT);
+
+        return 0 != *tags;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_get_cuesheet(const char *filename, FLAC__StreamMetadata **cuesheet)
+{
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != cuesheet);
+
+        *cuesheet = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_CUESHEET);
+
+        return 0 != *cuesheet;
+}
+
+FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
+{
+        (void)decoder, (void)frame, (void)buffer, (void)client_data;
+
+        return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
+}
+
+void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
+{
+        level0_client_data *cd = (level0_client_data *)client_data;
+        (void)decoder;
+
+        /*
+         * we assume we only get here when the one metadata block we were
+         * looking for was passed to us
+         */
+        if(!cd->got_error && 0 == cd->object) {
+                if(0 == (cd->object = FLAC__metadata_object_clone(metadata)))
+                        cd->got_error = true;
+        }
+}
+
+void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
+{
+        level0_client_data *cd = (level0_client_data *)client_data;
+        (void)decoder;
+
+        if(status != FLAC__STREAM_DECODER_ERROR_STATUS_LOST_SYNC)
+                cd->got_error = true;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_get_picture(const char *filename, FLAC__StreamMetadata **picture, FLAC__StreamMetadata_Picture_Type type, const char *mime_type, const FLAC__byte *description, unsigned max_width, unsigned max_height, unsigned max_depth, unsigned max_colors)
+{
+        FLAC__Metadata_SimpleIterator *it;
+        FLAC__uint64 max_area_seen = 0;
+        FLAC__uint64 max_depth_seen = 0;
+
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != picture);
+
+        *picture = 0;
+
+        it = FLAC__metadata_simple_iterator_new();
+        if(0 == it)
+                return false;
+        if(!FLAC__metadata_simple_iterator_init(it, filename, /*read_only=*/true, /*preserve_file_stats=*/true)) {
+                FLAC__metadata_simple_iterator_delete(it);
+                return false;
+        }
+        do {
+                if(FLAC__metadata_simple_iterator_get_block_type(it) == FLAC__METADATA_TYPE_PICTURE) {
+                        FLAC__StreamMetadata *obj = FLAC__metadata_simple_iterator_get_block(it);
+                        FLAC__uint64 area = (FLAC__uint64)obj->data.picture.width * (FLAC__uint64)obj->data.picture.height;
+                        /* check constraints */
+                        if(
+                                (type == (FLAC__StreamMetadata_Picture_Type)(-1) || type == obj->data.picture.type) &&
+                                (mime_type == 0 || !strcmp(mime_type, obj->data.picture.mime_type)) &&
+                                (description == 0 || !strcmp((const char *)description, (const char *)obj->data.picture.description)) &&
+                                obj->data.picture.width <= max_width &&
+                                obj->data.picture.height <= max_height &&
+                                obj->data.picture.depth <= max_depth &&
+                                obj->data.picture.colors <= max_colors &&
+                                (area > max_area_seen || (area == max_area_seen && obj->data.picture.depth > max_depth_seen))
+                        ) {
+                                if(*picture)
+                                        FLAC__metadata_object_delete(*picture);
+                                *picture = obj;
+                                max_area_seen = area;
+                                max_depth_seen = obj->data.picture.depth;
+                        }
+                        else {
+                                FLAC__metadata_object_delete(obj);
+                        }
+                }
+        } while(FLAC__metadata_simple_iterator_next(it));
+
+        FLAC__metadata_simple_iterator_delete(it);
+
+        return (0 != *picture);
+}
+
+
+/****************************************************************************
+ *
+ * Level 1 implementation
+ *
+ ***************************************************************************/
+
+#define SIMPLE_ITERATOR_MAX_PUSH_DEPTH (1+4)
+/* 1 for initial offset, +4 for our own personal use */
+
+struct FLAC__Metadata_SimpleIterator {
+        FILE *file;
+        char *filename, *tempfile_path_prefix;
+        struct flac_stat_s stats;
+        FLAC__bool has_stats;
+        FLAC__bool is_writable;
+        FLAC__Metadata_SimpleIteratorStatus status;
+        FLAC__off_t offset[SIMPLE_ITERATOR_MAX_PUSH_DEPTH];
+        FLAC__off_t first_offset; /* this is the offset to the STREAMINFO block */
+        unsigned depth;
+        /* this is the metadata block header of the current block we are pointing to: */
+        FLAC__bool is_last;
+        FLAC__MetadataType type;
+        unsigned length;
+};
+
+FLAC_API const char * const FLAC__Metadata_SimpleIteratorStatusString[] = {
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR",
+        "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR"
+};
+
+
+FLAC_API FLAC__Metadata_SimpleIterator *FLAC__metadata_simple_iterator_new(void)
+{
+        FLAC__Metadata_SimpleIterator *iterator = calloc(1, sizeof(FLAC__Metadata_SimpleIterator));
+
+        if(0 != iterator) {
+                iterator->file = 0;
+                iterator->filename = 0;
+                iterator->tempfile_path_prefix = 0;
+                iterator->has_stats = false;
+                iterator->is_writable = false;
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+                iterator->first_offset = iterator->offset[0] = -1;
+                iterator->depth = 0;
+        }
+
+        return iterator;
+}
+
+static void simple_iterator_free_guts_(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+
+        if(0 != iterator->file) {
+                fclose(iterator->file);
+                iterator->file = 0;
+                if(iterator->has_stats)
+                        set_file_stats_(iterator->filename, &iterator->stats);
+        }
+        if(0 != iterator->filename) {
+                free(iterator->filename);
+                iterator->filename = 0;
+        }
+        if(0 != iterator->tempfile_path_prefix) {
+                free(iterator->tempfile_path_prefix);
+                iterator->tempfile_path_prefix = 0;
+        }
+}
+
+FLAC_API void FLAC__metadata_simple_iterator_delete(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+
+        simple_iterator_free_guts_(iterator);
+        free(iterator);
+}
+
+FLAC_API FLAC__Metadata_SimpleIteratorStatus FLAC__metadata_simple_iterator_status(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__Metadata_SimpleIteratorStatus status;
+
+        FLAC__ASSERT(0 != iterator);
+
+        status = iterator->status;
+        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+        return status;
+}
+
+static FLAC__bool simple_iterator_prime_input_(FLAC__Metadata_SimpleIterator *iterator, FLAC__bool read_only)
+{
+        unsigned ret;
+
+        FLAC__ASSERT(0 != iterator);
+
+        if(read_only || 0 == (iterator->file = flac_fopen(iterator->filename, "r+b"))) {
+                iterator->is_writable = false;
+                if(read_only || errno == EACCES) {
+                        if(0 == (iterator->file = flac_fopen(iterator->filename, "rb"))) {
+                                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
+                                return false;
+                        }
+                }
+                else {
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
+                        return false;
+                }
+        }
+        else {
+                iterator->is_writable = true;
+        }
+
+        ret = seek_to_first_metadata_block_(iterator->file);
+        switch(ret) {
+                case 0:
+                        iterator->depth = 0;
+                        iterator->first_offset = iterator->offset[iterator->depth] = ftello(iterator->file);
+                        return read_metadata_block_header_(iterator);
+                case 1:
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                case 2:
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                        return false;
+                case 3:
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE;
+                        return false;
+                default:
+                        FLAC__ASSERT(0);
+                        return false;
+        }
+}
+
+#if 0
+@@@ If we decide to finish implementing this, put this comment back in metadata.h
+/*
+ * The 'tempfile_path_prefix' allows you to specify a directory where
+ * tempfiles should go.  Remember that if your metadata edits cause the
+ * FLAC file to grow, the entire file will have to be rewritten.  If
+ * 'tempfile_path_prefix' is NULL, the temp file will be written in the
+ * same directory as the original FLAC file.  This makes replacing the
+ * original with the tempfile fast but requires extra space in the same
+ * partition for the tempfile.  If space is a problem, you can pass a
+ * directory name belonging to a different partition in
+ * 'tempfile_path_prefix'.  Note that you should use the forward slash
+ * '/' as the directory separator.  A trailing slash is not needed; it
+ * will be added automatically.
+ */
+FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator *iterator, const char *filename, FLAC__bool preserve_file_stats, const char *tempfile_path_prefix);
+#endif
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator *iterator, const char *filename, FLAC__bool read_only, FLAC__bool preserve_file_stats)
+{
+        const char *tempfile_path_prefix = 0; /*@@@ search for comments near 'flac_rename(...)' for what it will take to finish implementing this */
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != filename);
+
+        simple_iterator_free_guts_(iterator);
+
+        if(!read_only && preserve_file_stats)
+                iterator->has_stats = get_file_stats_(filename, &iterator->stats);
+
+        if(0 == (iterator->filename = strdup(filename))) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+                return false;
+        }
+        if(0 != tempfile_path_prefix && 0 == (iterator->tempfile_path_prefix = strdup(tempfile_path_prefix))) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+                return false;
+        }
+
+        return simple_iterator_prime_input_(iterator, read_only);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_writable(const FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        return iterator->is_writable;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_next(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        if(iterator->is_last)
+                return false;
+
+        if(0 != fseeko(iterator->file, iterator->length, SEEK_CUR)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        iterator->offset[iterator->depth] = ftello(iterator->file);
+
+        return read_metadata_block_header_(iterator);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_prev(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__off_t this_offset;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        if(iterator->offset[iterator->depth] == iterator->first_offset)
+                return false;
+
+        if(0 != fseeko(iterator->file, iterator->first_offset, SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+        this_offset = iterator->first_offset;
+        if(!read_metadata_block_header_(iterator))
+                return false;
+
+        /* we ignore any error from ftello() and catch it in fseeko() */
+        while(ftello(iterator->file) + (FLAC__off_t)iterator->length < iterator->offset[iterator->depth]) {
+                if(0 != fseeko(iterator->file, iterator->length, SEEK_CUR)) {
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                        return false;
+                }
+                this_offset = ftello(iterator->file);
+                if(!read_metadata_block_header_(iterator))
+                        return false;
+        }
+
+        iterator->offset[iterator->depth] = this_offset;
+
+        return true;
+}
+
+/*@@@@add to tests*/
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_last(const FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        return iterator->is_last;
+}
+
+/*@@@@add to tests*/
+FLAC_API off_t FLAC__metadata_simple_iterator_get_block_offset(const FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        return iterator->offset[iterator->depth];
+}
+
+FLAC_API FLAC__MetadataType FLAC__metadata_simple_iterator_get_block_type(const FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        return iterator->type;
+}
+
+/*@@@@add to tests*/
+FLAC_API unsigned FLAC__metadata_simple_iterator_get_block_length(const FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        return iterator->length;
+}
+
+/*@@@@add to tests*/
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_get_application_id(FLAC__Metadata_SimpleIterator *iterator, FLAC__byte *id)
+{
+        const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+        FLAC__ASSERT(0 != id);
+
+        if(iterator->type != FLAC__METADATA_TYPE_APPLICATION) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
+                return false;
+        }
+
+        if(fread(id, 1, id_bytes, iterator->file) != id_bytes) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                return false;
+        }
+
+        /* back up */
+        if(0 != fseeko(iterator->file, -((int)id_bytes), SEEK_CUR)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        return true;
+}
+
+FLAC_API FLAC__StreamMetadata *FLAC__metadata_simple_iterator_get_block(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__StreamMetadata *block = FLAC__metadata_object_new(iterator->type);
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        if(0 != block) {
+                block->is_last = iterator->is_last;
+                block->length = iterator->length;
+
+                if(!read_metadata_block_data_(iterator, block)) {
+                        FLAC__metadata_object_delete(block);
+                        return 0;
+                }
+
+                /* back up to the beginning of the block data to stay consistent */
+                if(0 != fseeko(iterator->file, iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH, SEEK_SET)) {
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                        FLAC__metadata_object_delete(block);
+                        return 0;
+                }
+        }
+        else
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        return block;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_set_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding)
+{
+        FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth];)
+        FLAC__bool ret;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+        FLAC__ASSERT(0 != block);
+
+        if(!iterator->is_writable) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
+                return false;
+        }
+
+        if(iterator->type == FLAC__METADATA_TYPE_STREAMINFO || block->type == FLAC__METADATA_TYPE_STREAMINFO) {
+                if(iterator->type != block->type) {
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
+                        return false;
+                }
+        }
+
+        block->is_last = iterator->is_last;
+
+        if(iterator->length == block->length)
+                return write_metadata_block_stationary_(iterator, block);
+        else if(iterator->length > block->length) {
+                if(use_padding && iterator->length >= FLAC__STREAM_METADATA_HEADER_LENGTH + block->length) {
+                        ret = write_metadata_block_stationary_with_padding_(iterator, block, iterator->length - FLAC__STREAM_METADATA_HEADER_LENGTH - block->length, block->is_last);
+                        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
+                        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        return ret;
+                }
+                else {
+                        ret = rewrite_whole_file_(iterator, block, /*append=*/false);
+                        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
+                        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        return ret;
+                }
+        }
+        else /* iterator->length < block->length */ {
+                unsigned padding_leftover = 0;
+                FLAC__bool padding_is_last = false;
+                if(use_padding) {
+                        /* first see if we can even use padding */
+                        if(iterator->is_last) {
+                                use_padding = false;
+                        }
+                        else {
+                                const unsigned extra_padding_bytes_required = block->length - iterator->length;
+                                simple_iterator_push_(iterator);
+                                if(!FLAC__metadata_simple_iterator_next(iterator)) {
+                                        (void)simple_iterator_pop_(iterator);
+                                        return false;
+                                }
+                                if(iterator->type != FLAC__METADATA_TYPE_PADDING) {
+                                        use_padding = false;
+                                }
+                                else {
+                                        if(FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length == extra_padding_bytes_required) {
+                                                padding_leftover = 0;
+                                                block->is_last = iterator->is_last;
+                                        }
+                                        else if(iterator->length < extra_padding_bytes_required)
+                                                use_padding = false;
+                                        else {
+                                                padding_leftover = FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length - extra_padding_bytes_required;
+                                                padding_is_last = iterator->is_last;
+                                                block->is_last = false;
+                                        }
+                                }
+                                if(!simple_iterator_pop_(iterator))
+                                        return false;
+                        }
+                }
+                if(use_padding) {
+                        if(padding_leftover == 0) {
+                                ret = write_metadata_block_stationary_(iterator, block);
+                                FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
+                                FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                                return ret;
+                        }
+                        else {
+                                FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
+                                ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
+                                FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
+                                FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                                return ret;
+                        }
+                }
+                else {
+                        ret = rewrite_whole_file_(iterator, block, /*append=*/false);
+                        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
+                        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        return ret;
+                }
+        }
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_insert_block_after(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding)
+{
+        unsigned padding_leftover = 0;
+        FLAC__bool padding_is_last = false;
+
+        FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length;)
+        FLAC__bool ret;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+        FLAC__ASSERT(0 != block);
+
+        if(!iterator->is_writable) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
+                return false;
+        }
+
+        if(block->type == FLAC__METADATA_TYPE_STREAMINFO) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
+                return false;
+        }
+
+        block->is_last = iterator->is_last;
+
+        if(use_padding) {
+                /* first see if we can even use padding */
+                if(iterator->is_last) {
+                        use_padding = false;
+                }
+                else {
+                        simple_iterator_push_(iterator);
+                        if(!FLAC__metadata_simple_iterator_next(iterator)) {
+                                (void)simple_iterator_pop_(iterator);
+                                return false;
+                        }
+                        if(iterator->type != FLAC__METADATA_TYPE_PADDING) {
+                                use_padding = false;
+                        }
+                        else {
+                                if(iterator->length == block->length) {
+                                        padding_leftover = 0;
+                                        block->is_last = iterator->is_last;
+                                }
+                                else if(iterator->length < FLAC__STREAM_METADATA_HEADER_LENGTH + block->length)
+                                        use_padding = false;
+                                else {
+                                        padding_leftover = iterator->length - block->length;
+                                        padding_is_last = iterator->is_last;
+                                        block->is_last = false;
+                                }
+                        }
+                        if(!simple_iterator_pop_(iterator))
+                                return false;
+                }
+        }
+        if(use_padding) {
+                /* move to the next block, which is suitable padding */
+                if(!FLAC__metadata_simple_iterator_next(iterator))
+                        return false;
+                if(padding_leftover == 0) {
+                        ret = write_metadata_block_stationary_(iterator, block);
+                        FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
+                        FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        return ret;
+                }
+                else {
+                        FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
+                        FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
+                        FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                        return ret;
+                }
+        }
+        else {
+                ret = rewrite_whole_file_(iterator, block, /*append=*/true);
+                FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
+                FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
+                return ret;
+        }
+}
+
+FLAC_API FLAC__bool FLAC__metadata_simple_iterator_delete_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__bool use_padding)
+{
+        FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth];)
+        FLAC__bool ret;
+
+        if(iterator->type == FLAC__METADATA_TYPE_STREAMINFO) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
+                return false;
+        }
+
+        if(use_padding) {
+                FLAC__StreamMetadata *padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING);
+                if(0 == padding) {
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+                        return false;
+                }
+                padding->length = iterator->length;
+                if(!FLAC__metadata_simple_iterator_set_block(iterator, padding, false)) {
+                        FLAC__metadata_object_delete(padding);
+                        return false;
+                }
+                FLAC__metadata_object_delete(padding);
+                if(!FLAC__metadata_simple_iterator_prev(iterator))
+                        return false;
+                FLAC__ASSERT(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length == debug_target_offset);
+                FLAC__ASSERT(ftello(iterator->file) + (FLAC__off_t)iterator->length == debug_target_offset);
+                return true;
+        }
+        else {
+                ret = rewrite_whole_file_(iterator, 0, /*append=*/false);
+                FLAC__ASSERT(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length == debug_target_offset);
+                FLAC__ASSERT(ftello(iterator->file) + (FLAC__off_t)iterator->length == debug_target_offset);
+                return ret;
+        }
+}
+
+
+
+/****************************************************************************
+ *
+ * Level 2 implementation
+ *
+ ***************************************************************************/
+
+
+typedef struct FLAC__Metadata_Node {
+        FLAC__StreamMetadata *data;
+        struct FLAC__Metadata_Node *prev, *next;
+} FLAC__Metadata_Node;
+
+struct FLAC__Metadata_Chain {
+        char *filename; /* will be NULL if using callbacks */
+        FLAC__bool is_ogg;
+        FLAC__Metadata_Node *head;
+        FLAC__Metadata_Node *tail;
+        unsigned nodes;
+        FLAC__Metadata_ChainStatus status;
+        FLAC__off_t first_offset, last_offset;
+        /*
+         * This is the length of the chain initially read from the FLAC file.
+         * it is used to compare against the current length to decide whether
+         * or not the whole file has to be rewritten.
+         */
+        FLAC__off_t initial_length;
+        /* @@@ hacky, these are currently only needed by ogg reader */
+        FLAC__IOHandle handle;
+        FLAC__IOCallback_Read read_cb;
+};
+
+struct FLAC__Metadata_Iterator {
+        FLAC__Metadata_Chain *chain;
+        FLAC__Metadata_Node *current;
+};
+
+FLAC_API const char * const FLAC__Metadata_ChainStatusString[] = {
+        "FLAC__METADATA_CHAIN_STATUS_OK",
+        "FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT",
+        "FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE",
+        "FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE",
+        "FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE",
+        "FLAC__METADATA_CHAIN_STATUS_BAD_METADATA",
+        "FLAC__METADATA_CHAIN_STATUS_READ_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR",
+        "FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS",
+        "FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH",
+        "FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL"
+};
+
+
+static FLAC__Metadata_Node *node_new_(void)
+{
+        return calloc(1, sizeof(FLAC__Metadata_Node));
+}
+
+static void node_delete_(FLAC__Metadata_Node *node)
+{
+        FLAC__ASSERT(0 != node);
+        if(0 != node->data)
+                FLAC__metadata_object_delete(node->data);
+        free(node);
+}
+
+static void chain_init_(FLAC__Metadata_Chain *chain)
+{
+        FLAC__ASSERT(0 != chain);
+
+        chain->filename = 0;
+        chain->is_ogg = false;
+        chain->head = chain->tail = 0;
+        chain->nodes = 0;
+        chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
+        chain->initial_length = 0;
+        chain->read_cb = 0;
+}
+
+static void chain_clear_(FLAC__Metadata_Chain *chain)
+{
+        FLAC__Metadata_Node *node, *next;
+
+        FLAC__ASSERT(0 != chain);
+
+        for(node = chain->head; node; ) {
+                next = node->next;
+                node_delete_(node);
+                node = next;
+        }
+
+        if(0 != chain->filename)
+                free(chain->filename);
+
+        chain_init_(chain);
+}
+
+static void chain_append_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
+{
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != node);
+        FLAC__ASSERT(0 != node->data);
+
+        node->next = node->prev = 0;
+        node->data->is_last = true;
+        if(0 != chain->tail)
+                chain->tail->data->is_last = false;
+
+        if(0 == chain->head)
+                chain->head = node;
+        else {
+                FLAC__ASSERT(0 != chain->tail);
+                chain->tail->next = node;
+                node->prev = chain->tail;
+        }
+        chain->tail = node;
+        chain->nodes++;
+}
+
+static void chain_remove_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
+{
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != node);
+
+        if(node == chain->head)
+                chain->head = node->next;
+        else
+                node->prev->next = node->next;
+
+        if(node == chain->tail)
+                chain->tail = node->prev;
+        else
+                node->next->prev = node->prev;
+
+        if(0 != chain->tail)
+                chain->tail->data->is_last = true;
+
+        chain->nodes--;
+}
+
+static void chain_delete_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
+{
+        chain_remove_node_(chain, node);
+        node_delete_(node);
+}
+
+static FLAC__off_t chain_calculate_length_(FLAC__Metadata_Chain *chain)
+{
+        const FLAC__Metadata_Node *node;
+        FLAC__off_t length = 0;
+        for(node = chain->head; node; node = node->next)
+                length += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
+        return length;
+}
+
+static void iterator_insert_node_(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Node *node)
+{
+        FLAC__ASSERT(0 != node);
+        FLAC__ASSERT(0 != node->data);
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+        FLAC__ASSERT(0 != iterator->chain);
+        FLAC__ASSERT(0 != iterator->chain->head);
+        FLAC__ASSERT(0 != iterator->chain->tail);
+
+        node->data->is_last = false;
+
+        node->prev = iterator->current->prev;
+        node->next = iterator->current;
+
+        if(0 == node->prev)
+                iterator->chain->head = node;
+        else
+                node->prev->next = node;
+
+        iterator->current->prev = node;
+
+        iterator->chain->nodes++;
+}
+
+static void iterator_insert_node_after_(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Node *node)
+{
+        FLAC__ASSERT(0 != node);
+        FLAC__ASSERT(0 != node->data);
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+        FLAC__ASSERT(0 != iterator->chain);
+        FLAC__ASSERT(0 != iterator->chain->head);
+        FLAC__ASSERT(0 != iterator->chain->tail);
+
+        iterator->current->data->is_last = false;
+
+        node->prev = iterator->current;
+        node->next = iterator->current->next;
+
+        if(0 == node->next)
+                iterator->chain->tail = node;
+        else
+                node->next->prev = node;
+
+        node->prev->next = node;
+
+        iterator->chain->tail->data->is_last = true;
+
+        iterator->chain->nodes++;
+}
+
+/* return true iff node and node->next are both padding */
+static FLAC__bool chain_merge_adjacent_padding_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
+{
+        if(node->data->type == FLAC__METADATA_TYPE_PADDING && 0 != node->next && node->next->data->type == FLAC__METADATA_TYPE_PADDING) {
+                const unsigned growth = FLAC__STREAM_METADATA_HEADER_LENGTH + node->next->data->length;
+                node->data->length += growth;
+
+                chain_delete_node_(chain, node->next);
+                return true;
+        }
+        else
+                return false;
+}
+
+/* Returns the new length of the chain, or 0 if there was an error. */
+/* WATCHOUT: This can get called multiple times before a write, so
+ * it should still work when this happens.
+ */
+/* WATCHOUT: Make sure to also update the logic in
+ * FLAC__metadata_chain_check_if_tempfile_needed() if the logic here changes.
+ */
+static FLAC__off_t chain_prepare_for_write_(FLAC__Metadata_Chain *chain, FLAC__bool use_padding)
+{
+        FLAC__off_t current_length = chain_calculate_length_(chain);
+
+        if(use_padding) {
+                /* if the metadata shrank and the last block is padding, we just extend the last padding block */
+                if(current_length < chain->initial_length && chain->tail->data->type == FLAC__METADATA_TYPE_PADDING) {
+                        const FLAC__off_t delta = chain->initial_length - current_length;
+                        chain->tail->data->length += delta;
+                        current_length += delta;
+                        FLAC__ASSERT(current_length == chain->initial_length);
+                }
+                /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
+                else if(current_length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length) {
+                        FLAC__StreamMetadata *padding;
+                        FLAC__Metadata_Node *node;
+                        if(0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING))) {
+                                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                                return 0;
+                        }
+                        padding->length = chain->initial_length - (FLAC__STREAM_METADATA_HEADER_LENGTH + current_length);
+                        if(0 == (node = node_new_())) {
+                                FLAC__metadata_object_delete(padding);
+                                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                                return 0;
+                        }
+                        node->data = padding;
+                        chain_append_node_(chain, node);
+                        current_length = chain_calculate_length_(chain);
+                        FLAC__ASSERT(current_length == chain->initial_length);
+                }
+                /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
+                else if(current_length > chain->initial_length) {
+                        const FLAC__off_t delta = current_length - chain->initial_length;
+                        if(chain->tail->data->type == FLAC__METADATA_TYPE_PADDING) {
+                                /* if the delta is exactly the size of the last padding block, remove the padding block */
+                                if((FLAC__off_t)chain->tail->data->length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta) {
+                                        chain_delete_node_(chain, chain->tail);
+                                        current_length = chain_calculate_length_(chain);
+                                        FLAC__ASSERT(current_length == chain->initial_length);
+                                }
+                                /* if there is at least 'delta' bytes of padding, trim the padding down */
+                                else if((FLAC__off_t)chain->tail->data->length >= delta) {
+                                        chain->tail->data->length -= delta;
+                                        current_length -= delta;
+                                        FLAC__ASSERT(current_length == chain->initial_length);
+                                }
+                        }
+                }
+        }
+
+        return current_length;
+}
+
+static FLAC__bool chain_read_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Tell tell_cb)
+{
+        FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != chain);
+
+        /* we assume we're already at the beginning of the file */
+
+        switch(seek_to_first_metadata_block_cb_(handle, read_cb, seek_cb)) {
+                case 0:
+                        break;
+                case 1:
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
+                        return false;
+                case 2:
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                        return false;
+                case 3:
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
+                        return false;
+                default:
+                        FLAC__ASSERT(0);
+                        return false;
+        }
+
+        {
+                FLAC__int64 pos = tell_cb(handle);
+                if(pos < 0) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
+                        return false;
+                }
+                chain->first_offset = (FLAC__off_t)pos;
+        }
+
+        {
+                FLAC__bool is_last;
+                FLAC__MetadataType type;
+                unsigned length;
+
+                do {
+                        node = node_new_();
+                        if(0 == node) {
+                                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                                return false;
+                        }
+
+                        if(!read_metadata_block_header_cb_(handle, read_cb, &is_last, &type, &length)) {
+                                node_delete_(node);
+                                chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
+                                return false;
+                        }
+
+                        node->data = FLAC__metadata_object_new(type);
+                        if(0 == node->data) {
+                                node_delete_(node);
+                                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                                return false;
+                        }
+
+                        node->data->is_last = is_last;
+                        node->data->length = length;
+
+                        chain->status = get_equivalent_status_(read_metadata_block_data_cb_(handle, read_cb, seek_cb, node->data));
+                        if(chain->status != FLAC__METADATA_CHAIN_STATUS_OK) {
+                                node_delete_(node);
+                                return false;
+                        }
+                        chain_append_node_(chain, node);
+                } while(!is_last);
+        }
+
+        {
+                FLAC__int64 pos = tell_cb(handle);
+                if(pos < 0) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
+                        return false;
+                }
+                chain->last_offset = (FLAC__off_t)pos;
+        }
+
+        chain->initial_length = chain_calculate_length_(chain);
+
+        return true;
+}
+
+static FLAC__StreamDecoderReadStatus chain_read_ogg_read_cb_(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], size_t *bytes, void *client_data)
+{
+        FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
+        (void)decoder;
+        if(*bytes > 0 && chain->status == FLAC__METADATA_CHAIN_STATUS_OK) {
+                *bytes = chain->read_cb(buffer, sizeof(FLAC__byte), *bytes, chain->handle);
+                if(*bytes == 0)
+                        return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
+                else
+                        return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
+        }
+        else
+                return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
+}
+
+static FLAC__StreamDecoderWriteStatus chain_read_ogg_write_cb_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
+{
+        (void)decoder, (void)frame, (void)buffer, (void)client_data;
+        return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;
+}
+
+static void chain_read_ogg_metadata_cb_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
+{
+        FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
+        FLAC__Metadata_Node *node;
+
+        (void)decoder;
+
+        node = node_new_();
+        if(0 == node) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                return;
+        }
+
+        node->data = FLAC__metadata_object_clone(metadata);
+        if(0 == node->data) {
+                node_delete_(node);
+                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                return;
+        }
+
+        chain_append_node_(chain, node);
+}
+
+static void chain_read_ogg_error_cb_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
+{
+        FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
+        (void)decoder, (void)status;
+        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
+}
+
+static FLAC__bool chain_read_ogg_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb)
+{
+        FLAC__StreamDecoder *decoder;
+
+        FLAC__ASSERT(0 != chain);
+
+        /* we assume we're already at the beginning of the file */
+
+        chain->handle = handle;
+        chain->read_cb = read_cb;
+        if(0 == (decoder = FLAC__stream_decoder_new())) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                return false;
+        }
+        FLAC__stream_decoder_set_metadata_respond_all(decoder);
+        if(FLAC__stream_decoder_init_ogg_stream(decoder, chain_read_ogg_read_cb_, /*seek_callback=*/0, /*tell_callback=*/0, /*length_callback=*/0, /*eof_callback=*/0, chain_read_ogg_write_cb_, chain_read_ogg_metadata_cb_, chain_read_ogg_error_cb_, chain) != FLAC__STREAM_DECODER_INIT_STATUS_OK) {
+                FLAC__stream_decoder_delete(decoder);
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
+                return false;
+        }
+
+        chain->first_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */
+
+        if(!FLAC__stream_decoder_process_until_end_of_metadata(decoder))
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
+        if(chain->status != FLAC__METADATA_CHAIN_STATUS_OK) {
+                FLAC__stream_decoder_delete(decoder);
+                return false;
+        }
+
+        FLAC__stream_decoder_delete(decoder);
+
+        chain->last_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */
+
+        chain->initial_length = chain_calculate_length_(chain);
+
+        return true;
+}
+
+static FLAC__bool chain_rewrite_metadata_in_place_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, FLAC__IOCallback_Seek seek_cb)
+{
+        FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != chain->head);
+
+        if(0 != seek_cb(handle, chain->first_offset, SEEK_SET)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        for(node = chain->head; node; node = node->next) {
+                if(!write_metadata_block_header_cb_(handle, write_cb, node->data)) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
+                        return false;
+                }
+                if(!write_metadata_block_data_cb_(handle, write_cb, node->data)) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
+                        return false;
+                }
+        }
+
+        /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/
+
+        chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
+        return true;
+}
+
+static FLAC__bool chain_rewrite_metadata_in_place_(FLAC__Metadata_Chain *chain)
+{
+        FILE *file;
+        FLAC__bool ret;
+
+        FLAC__ASSERT(0 != chain->filename);
+
+        if(0 == (file = flac_fopen(chain->filename, "r+b"))) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
+                return false;
+        }
+
+        /* chain_rewrite_metadata_in_place_cb_() sets chain->status for us */
+        ret = chain_rewrite_metadata_in_place_cb_(chain, (FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, fseek_wrapper_);
+
+        fclose(file);
+
+        return ret;
+}
+
+static FLAC__bool chain_rewrite_file_(FLAC__Metadata_Chain *chain, const char *tempfile_path_prefix)
+{
+        FILE *f, *tempfile = NULL;
+        char *tempfilename;
+        FLAC__Metadata_SimpleIteratorStatus status;
+        const FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != chain->filename);
+        FLAC__ASSERT(0 != chain->head);
+
+        /* copy the file prefix (data up to first metadata block */
+        if(0 == (f = flac_fopen(chain->filename, "rb"))) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
+                return false;
+        }
+        if(!open_tempfile_(chain->filename, tempfile_path_prefix, &tempfile, &tempfilename, &status)) {
+                chain->status = get_equivalent_status_(status);
+                goto err;
+        }
+        if(!copy_n_bytes_from_file_(f, tempfile, chain->first_offset, &status)) {
+                chain->status = get_equivalent_status_(status);
+                goto err;
+        }
+
+        /* write the metadata */
+        for(node = chain->head; node; node = node->next) {
+                if(!write_metadata_block_header_(tempfile, &status, node->data)) {
+                        chain->status = get_equivalent_status_(status);
+                        goto err;
+                }
+                if(!write_metadata_block_data_(tempfile, &status, node->data)) {
+                        chain->status = get_equivalent_status_(status);
+                        goto err;
+                }
+        }
+        /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/
+
+        /* copy the file postfix (everything after the metadata) */
+        if(0 != fseeko(f, chain->last_offset, SEEK_SET)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                goto err;
+        }
+        if(!copy_remaining_bytes_from_file_(f, tempfile, &status)) {
+                chain->status = get_equivalent_status_(status);
+                goto err;
+        }
+
+        /* move the tempfile on top of the original */
+        (void)fclose(f);
+        if(!transport_tempfile_(chain->filename, &tempfile, &tempfilename, &status))
+                return false;
+
+        return true;
+
+err:
+        (void)fclose(f);
+        cleanup_tempfile_(&tempfile, &tempfilename);
+        return false;
+}
+
+/* assumes 'handle' is already at beginning of file */
+static FLAC__bool chain_rewrite_file_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb)
+{
+        FLAC__Metadata_SimpleIteratorStatus status;
+        const FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 == chain->filename);
+        FLAC__ASSERT(0 != chain->head);
+
+        /* copy the file prefix (data up to first metadata block */
+        if(!copy_n_bytes_from_file_cb_(handle, read_cb, temp_handle, temp_write_cb, chain->first_offset, &status)) {
+                chain->status = get_equivalent_status_(status);
+                return false;
+        }
+
+        /* write the metadata */
+        for(node = chain->head; node; node = node->next) {
+                if(!write_metadata_block_header_cb_(temp_handle, temp_write_cb, node->data)) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
+                        return false;
+                }
+                if(!write_metadata_block_data_cb_(temp_handle, temp_write_cb, node->data)) {
+                        chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
+                        return false;
+                }
+        }
+        /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/
+
+        /* copy the file postfix (everything after the metadata) */
+        if(0 != seek_cb(handle, chain->last_offset, SEEK_SET)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                return false;
+        }
+        if(!copy_remaining_bytes_from_file_cb_(handle, read_cb, eof_cb, temp_handle, temp_write_cb, &status)) {
+                chain->status = get_equivalent_status_(status);
+                return false;
+        }
+
+        return true;
+}
+
+FLAC_API FLAC__Metadata_Chain *FLAC__metadata_chain_new(void)
+{
+        FLAC__Metadata_Chain *chain = calloc(1, sizeof(FLAC__Metadata_Chain));
+
+        if(0 != chain)
+                chain_init_(chain);
+
+        return chain;
+}
+
+FLAC_API void FLAC__metadata_chain_delete(FLAC__Metadata_Chain *chain)
+{
+        FLAC__ASSERT(0 != chain);
+
+        chain_clear_(chain);
+
+        free(chain);
+}
+
+FLAC_API FLAC__Metadata_ChainStatus FLAC__metadata_chain_status(FLAC__Metadata_Chain *chain)
+{
+        FLAC__Metadata_ChainStatus status;
+
+        FLAC__ASSERT(0 != chain);
+
+        status = chain->status;
+        chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
+        return status;
+}
+
+static FLAC__bool chain_read_(FLAC__Metadata_Chain *chain, const char *filename, FLAC__bool is_ogg)
+{
+        FILE *file;
+        FLAC__bool ret;
+
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != filename);
+
+        chain_clear_(chain);
+
+        if(0 == (chain->filename = strdup(filename))) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                return false;
+        }
+
+        chain->is_ogg = is_ogg;
+
+        if(0 == (file = flac_fopen(filename, "rb"))) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
+                return false;
+        }
+
+        /* the function also sets chain->status for us */
+        ret = is_ogg?
+                chain_read_ogg_cb_(chain, file, (FLAC__IOCallback_Read)fread) :
+                chain_read_cb_(chain, file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, ftell_wrapper_)
+        ;
+
+        fclose(file);
+
+        return ret;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_read(FLAC__Metadata_Chain *chain, const char *filename)
+{
+        return chain_read_(chain, filename, /*is_ogg=*/false);
+}
+
+/*@@@@add to tests*/
+FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg(FLAC__Metadata_Chain *chain, const char *filename)
+{
+        return chain_read_(chain, filename, /*is_ogg=*/true);
+}
+
+static FLAC__bool chain_read_with_callbacks_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__bool is_ogg)
+{
+        FLAC__bool ret;
+
+        FLAC__ASSERT(0 != chain);
+
+        chain_clear_(chain);
+
+        if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.tell) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
+                return false;
+        }
+
+        chain->is_ogg = is_ogg;
+
+        /* rewind */
+        if(0 != callbacks.seek(handle, 0, SEEK_SET)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        /* the function also sets chain->status for us */
+        ret = is_ogg?
+                chain_read_ogg_cb_(chain, handle, callbacks.read) :
+                chain_read_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.tell)
+        ;
+
+        return ret;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_read_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
+{
+        return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/false);
+}
+
+/*@@@@add to tests*/
+FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
+{
+        return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/true);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_check_if_tempfile_needed(FLAC__Metadata_Chain *chain, FLAC__bool use_padding)
+{
+        /* This does all the same checks that are in chain_prepare_for_write_()
+         * but doesn't actually alter the chain.  Make sure to update the logic
+         * here if chain_prepare_for_write_() changes.
+         */
+        const FLAC__off_t current_length = chain_calculate_length_(chain);
+
+        FLAC__ASSERT(0 != chain);
+
+        if(use_padding) {
+                /* if the metadata shrank and the last block is padding, we just extend the last padding block */
+                if(current_length < chain->initial_length && chain->tail->data->type == FLAC__METADATA_TYPE_PADDING)
+                        return false;
+                /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
+                else if(current_length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length)
+                        return false;
+                /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
+                else if(current_length > chain->initial_length) {
+                        const FLAC__off_t delta = current_length - chain->initial_length;
+                        if(chain->tail->data->type == FLAC__METADATA_TYPE_PADDING) {
+                                /* if the delta is exactly the size of the last padding block, remove the padding block */
+                                if((FLAC__off_t)chain->tail->data->length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta)
+                                        return false;
+                                /* if there is at least 'delta' bytes of padding, trim the padding down */
+                                else if((FLAC__off_t)chain->tail->data->length >= delta)
+                                        return false;
+                        }
+                }
+        }
+
+        return (current_length != chain->initial_length);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_write(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__bool preserve_file_stats)
+{
+        struct flac_stat_s stats;
+        const char *tempfile_path_prefix = 0;
+        FLAC__off_t current_length;
+
+        FLAC__ASSERT(0 != chain);
+
+        if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
+                return false;
+        }
+
+        if (0 == chain->filename) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
+                return false;
+        }
+
+        current_length = chain_prepare_for_write_(chain, use_padding);
+
+        /* a return value of 0 means there was an error; chain->status is already set */
+        if (0 == current_length)
+                return false;
+
+        if(preserve_file_stats)
+                get_file_stats_(chain->filename, &stats);
+
+        if(current_length == chain->initial_length) {
+                if(!chain_rewrite_metadata_in_place_(chain))
+                        return false;
+        }
+        else {
+                if(!chain_rewrite_file_(chain, tempfile_path_prefix))
+                        return false;
+
+                /* recompute lengths and offsets */
+                {
+                        const FLAC__Metadata_Node *node;
+                        chain->initial_length = current_length;
+                        chain->last_offset = chain->first_offset;
+                        for(node = chain->head; node; node = node->next)
+                                chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
+                }
+        }
+
+        if(preserve_file_stats)
+                set_file_stats_(chain->filename, &stats);
+
+        return true;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
+{
+        FLAC__off_t current_length;
+
+        FLAC__ASSERT(0 != chain);
+
+        if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
+                return false;
+        }
+
+        if (0 != chain->filename) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
+                return false;
+        }
+
+        if (0 == callbacks.write || 0 == callbacks.seek) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
+                return false;
+        }
+
+        if (FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
+                return false;
+        }
+
+        current_length = chain_prepare_for_write_(chain, use_padding);
+
+        /* a return value of 0 means there was an error; chain->status is already set */
+        if (0 == current_length)
+                return false;
+
+        FLAC__ASSERT(current_length == chain->initial_length);
+
+        return chain_rewrite_metadata_in_place_cb_(chain, handle, callbacks.write, callbacks.seek);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks_and_tempfile(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__IOHandle temp_handle, FLAC__IOCallbacks temp_callbacks)
+{
+        FLAC__off_t current_length;
+
+        FLAC__ASSERT(0 != chain);
+
+        if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
+                return false;
+        }
+
+        if (0 != chain->filename) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
+                return false;
+        }
+
+        if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.eof) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
+                return false;
+        }
+        if (0 == temp_callbacks.write) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
+                return false;
+        }
+
+        if (!FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
+                return false;
+        }
+
+        current_length = chain_prepare_for_write_(chain, use_padding);
+
+        /* a return value of 0 means there was an error; chain->status is already set */
+        if (0 == current_length)
+                return false;
+
+        FLAC__ASSERT(current_length != chain->initial_length);
+
+        /* rewind */
+        if(0 != callbacks.seek(handle, 0, SEEK_SET)) {
+                chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        if(!chain_rewrite_file_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.eof, temp_handle, temp_callbacks.write))
+                return false;
+
+        /* recompute lengths and offsets */
+        {
+                const FLAC__Metadata_Node *node;
+                chain->initial_length = current_length;
+                chain->last_offset = chain->first_offset;
+                for(node = chain->head; node; node = node->next)
+                        chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
+        }
+
+        return true;
+}
+
+FLAC_API void FLAC__metadata_chain_merge_padding(FLAC__Metadata_Chain *chain)
+{
+        FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != chain);
+
+        for(node = chain->head; node; ) {
+                if(!chain_merge_adjacent_padding_(chain, node))
+                        node = node->next;
+        }
+}
+
+FLAC_API void FLAC__metadata_chain_sort_padding(FLAC__Metadata_Chain *chain)
+{
+        FLAC__Metadata_Node *node, *save;
+        unsigned i;
+
+        FLAC__ASSERT(0 != chain);
+
+        /*
+         * Don't try and be too smart... this simple algo is good enough for
+         * the small number of nodes that we deal with.
+         */
+        for(i = 0, node = chain->head; i < chain->nodes; i++) {
+                if(node->data->type == FLAC__METADATA_TYPE_PADDING) {
+                        save = node->next;
+                        chain_remove_node_(chain, node);
+                        chain_append_node_(chain, node);
+                        node = save;
+                }
+                else {
+                        node = node->next;
+                }
+        }
+
+        FLAC__metadata_chain_merge_padding(chain);
+}
+
+
+FLAC_API FLAC__Metadata_Iterator *FLAC__metadata_iterator_new(void)
+{
+        FLAC__Metadata_Iterator *iterator = calloc(1, sizeof(FLAC__Metadata_Iterator));
+
+        /* calloc() implies:
+                iterator->current = 0;
+                iterator->chain = 0;
+        */
+
+        return iterator;
+}
+
+FLAC_API void FLAC__metadata_iterator_delete(FLAC__Metadata_Iterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+
+        free(iterator);
+}
+
+FLAC_API void FLAC__metadata_iterator_init(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Chain *chain)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != chain);
+        FLAC__ASSERT(0 != chain->head);
+
+        iterator->chain = chain;
+        iterator->current = chain->head;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_next(FLAC__Metadata_Iterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+
+        if(0 == iterator->current || 0 == iterator->current->next)
+                return false;
+
+        iterator->current = iterator->current->next;
+        return true;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_prev(FLAC__Metadata_Iterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+
+        if(0 == iterator->current || 0 == iterator->current->prev)
+                return false;
+
+        iterator->current = iterator->current->prev;
+        return true;
+}
+
+FLAC_API FLAC__MetadataType FLAC__metadata_iterator_get_block_type(const FLAC__Metadata_Iterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+        FLAC__ASSERT(0 != iterator->current->data);
+
+        return iterator->current->data->type;
+}
+
+FLAC_API FLAC__StreamMetadata *FLAC__metadata_iterator_get_block(FLAC__Metadata_Iterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+
+        return iterator->current->data;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_set_block(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != block);
+        return FLAC__metadata_iterator_delete_block(iterator, false) && FLAC__metadata_iterator_insert_block_after(iterator, block);
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_delete_block(FLAC__Metadata_Iterator *iterator, FLAC__bool replace_with_padding)
+{
+        FLAC__Metadata_Node *save;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+
+        if(0 == iterator->current->prev) {
+                FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
+                return false;
+        }
+
+        save = iterator->current->prev;
+
+        if(replace_with_padding) {
+                FLAC__metadata_object_delete_data(iterator->current->data);
+                iterator->current->data->type = FLAC__METADATA_TYPE_PADDING;
+        }
+        else {
+                chain_delete_node_(iterator->chain, iterator->current);
+        }
+
+        iterator->current = save;
+        return true;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_before(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
+{
+        FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+        FLAC__ASSERT(0 != block);
+
+        if(block->type == FLAC__METADATA_TYPE_STREAMINFO)
+                return false;
+
+        if(0 == iterator->current->prev) {
+                FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
+                return false;
+        }
+
+        if(0 == (node = node_new_()))
+                return false;
+
+        node->data = block;
+        iterator_insert_node_(iterator, node);
+        iterator->current = node;
+        return true;
+}
+
+FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_after(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
+{
+        FLAC__Metadata_Node *node;
+
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->current);
+        FLAC__ASSERT(0 != block);
+
+        if(block->type == FLAC__METADATA_TYPE_STREAMINFO)
+                return false;
+
+        if(0 == (node = node_new_()))
+                return false;
+
+        node->data = block;
+        iterator_insert_node_after_(iterator, node);
+        iterator->current = node;
+        return true;
+}
+
+
+/****************************************************************************
+ *
+ * Local function definitions
+ *
+ ***************************************************************************/
+
+void pack_uint32_(FLAC__uint32 val, FLAC__byte *b, unsigned bytes)
+{
+        unsigned i;
+
+        b += bytes;
+
+        for(i = 0; i < bytes; i++) {
+                *(--b) = (FLAC__byte)(val & 0xff);
+                val >>= 8;
+        }
+}
+
+void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte *b, unsigned bytes)
+{
+        unsigned i;
+
+        for(i = 0; i < bytes; i++) {
+                *(b++) = (FLAC__byte)(val & 0xff);
+                val >>= 8;
+        }
+}
+
+void pack_uint64_(FLAC__uint64 val, FLAC__byte *b, unsigned bytes)
+{
+        unsigned i;
+
+        b += bytes;
+
+        for(i = 0; i < bytes; i++) {
+                *(--b) = (FLAC__byte)(val & 0xff);
+                val >>= 8;
+        }
+}
+
+FLAC__uint32 unpack_uint32_(FLAC__byte *b, unsigned bytes)
+{
+        FLAC__uint32 ret = 0;
+        unsigned i;
+
+        for(i = 0; i < bytes; i++)
+                ret = (ret << 8) | (FLAC__uint32)(*b++);
+
+        return ret;
+}
+
+FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte *b, unsigned bytes)
+{
+        FLAC__uint32 ret = 0;
+        unsigned i;
+
+        b += bytes;
+
+        for(i = 0; i < bytes; i++)
+                ret = (ret << 8) | (FLAC__uint32)(*--b);
+
+        return ret;
+}
+
+FLAC__uint64 unpack_uint64_(FLAC__byte *b, unsigned bytes)
+{
+        FLAC__uint64 ret = 0;
+        unsigned i;
+
+        for(i = 0; i < bytes; i++)
+                ret = (ret << 8) | (FLAC__uint64)(*b++);
+
+        return ret;
+}
+
+FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        if(!read_metadata_block_header_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, &iterator->is_last, &iterator->type, &iterator->length)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                return false;
+        }
+
+        return true;
+}
+
+FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block)
+{
+        FLAC__ASSERT(0 != iterator);
+        FLAC__ASSERT(0 != iterator->file);
+
+        iterator->status = read_metadata_block_data_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, block);
+
+        return (iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);
+}
+
+FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool *is_last, FLAC__MetadataType *type, unsigned *length)
+{
+        FLAC__byte raw_header[FLAC__STREAM_METADATA_HEADER_LENGTH];
+
+        if(read_cb(raw_header, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
+                return false;
+
+        *is_last = raw_header[0] & 0x80? true : false;
+        *type = (FLAC__MetadataType)(raw_header[0] & 0x7f);
+        *length = unpack_uint32_(raw_header + 1, 3);
+
+        /* Note that we don't check:
+         *    if(iterator->type >= FLAC__METADATA_TYPE_UNDEFINED)
+         * we just will read in an opaque block
+         */
+
+        return true;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata *block)
+{
+        switch(block->type) {
+                case FLAC__METADATA_TYPE_STREAMINFO:
+                        return read_metadata_block_data_streaminfo_cb_(handle, read_cb, &block->data.stream_info);
+                case FLAC__METADATA_TYPE_PADDING:
+                        return read_metadata_block_data_padding_cb_(handle, seek_cb, &block->data.padding, block->length);
+                case FLAC__METADATA_TYPE_APPLICATION:
+                        return read_metadata_block_data_application_cb_(handle, read_cb, &block->data.application, block->length);
+                case FLAC__METADATA_TYPE_SEEKTABLE:
+                        return read_metadata_block_data_seektable_cb_(handle, read_cb, &block->data.seek_table, block->length);
+                case FLAC__METADATA_TYPE_VORBIS_COMMENT:
+                        return read_metadata_block_data_vorbis_comment_cb_(handle, read_cb, seek_cb, &block->data.vorbis_comment, block->length);
+                case FLAC__METADATA_TYPE_CUESHEET:
+                        return read_metadata_block_data_cuesheet_cb_(handle, read_cb, &block->data.cue_sheet);
+                case FLAC__METADATA_TYPE_PICTURE:
+                        return read_metadata_block_data_picture_cb_(handle, read_cb, &block->data.picture);
+                default:
+                        return read_metadata_block_data_unknown_cb_(handle, read_cb, &block->data.unknown, block->length);
+        }
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo *block)
+{
+        FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH], *b;
+
+        if(read_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+        b = buffer;
+
+        /* we are using hardcoded numbers for simplicity but we should
+         * probably eventually write a bit-level unpacker and use the
+         * _STREAMINFO_ constants.
+         */
+        block->min_blocksize = unpack_uint32_(b, 2); b += 2;
+        block->max_blocksize = unpack_uint32_(b, 2); b += 2;
+        block->min_framesize = unpack_uint32_(b, 3); b += 3;
+        block->max_framesize = unpack_uint32_(b, 3); b += 3;
+        block->sample_rate = (unpack_uint32_(b, 2) << 4) | ((unsigned)(b[2] & 0xf0) >> 4);
+        block->channels = (unsigned)((b[2] & 0x0e) >> 1) + 1;
+        block->bits_per_sample = ((((unsigned)(b[2] & 0x01)) << 4) | (((unsigned)(b[3] & 0xf0)) >> 4)) + 1;
+        block->total_samples = (((FLAC__uint64)(b[3] & 0x0f)) << 32) | unpack_uint64_(b+4, 4);
+        memcpy(block->md5sum, b+8, 16);
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding *block, unsigned block_length)
+{
+        (void)block; /* nothing to do; we don't care about reading the padding bytes */
+
+        if(0 != seek_cb(handle, block_length, SEEK_CUR))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application *block, unsigned block_length)
+{
+        const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;
+
+        if(read_cb(block->id, 1, id_bytes, handle) != id_bytes)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+        if(block_length < id_bytes)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+        block_length -= id_bytes;
+
+        if(block_length == 0) {
+                block->data = 0;
+        }
+        else {
+                if(0 == (block->data = malloc(block_length)))
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+                if(read_cb(block->data, 1, block_length, handle) != block_length)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable *block, unsigned block_length)
+{
+        unsigned i;
+        FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];
+
+        FLAC__ASSERT(block_length % FLAC__STREAM_METADATA_SEEKPOINT_LENGTH == 0);
+
+        block->num_points = block_length / FLAC__STREAM_METADATA_SEEKPOINT_LENGTH;
+
+        if(block->num_points == 0)
+                block->points = 0;
+        else if(0 == (block->points = safe_malloc_mul_2op_p(block->num_points, /*times*/sizeof(FLAC__StreamMetadata_SeekPoint))))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        for(i = 0; i < block->num_points; i++) {
+                if(read_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                /* some MAGIC NUMBERs here */
+                block->points[i].sample_number = unpack_uint64_(buffer, 8);
+                block->points[i].stream_offset = unpack_uint64_(buffer+8, 8);
+                block->points[i].frame_samples = unpack_uint32_(buffer+16, 2);
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, unsigned max_length)
+{
+        const unsigned entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
+        FLAC__byte buffer[4]; /* magic number is asserted below */
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8 == sizeof(buffer));
+
+        if(max_length < entry_length_len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
+
+        max_length -= entry_length_len;
+        if(read_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        entry->length = unpack_uint32_little_endian_(buffer, entry_length_len);
+        if(max_length < entry->length) {
+                entry->length = 0;
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
+        } else max_length -= entry->length;
+
+        if(0 != entry->entry)
+                free(entry->entry);
+
+        if(entry->length == 0) {
+                entry->entry = 0;
+        }
+        else {
+                if(0 == (entry->entry = safe_malloc_add_2op_(entry->length, /*+*/1)))
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+                if(read_cb(entry->entry, 1, entry->length, handle) != entry->length)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+                entry->entry[entry->length] = '\0';
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_VorbisComment *block, unsigned block_length)
+{
+        unsigned i;
+        FLAC__Metadata_SimpleIteratorStatus status;
+        const unsigned num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
+        FLAC__byte buffer[4]; /* magic number is asserted below */
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8 == sizeof(buffer));
+
+        status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, &(block->vendor_string), block_length);
+        if(block_length >= 4)
+                block_length -= 4;
+        if(status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA)
+                goto skip;
+        else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
+                return status;
+        block_length -= block->vendor_string.length;
+
+        if(block_length < num_comments_len) goto skip; else block_length -= num_comments_len;
+        if(read_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->num_comments = unpack_uint32_little_endian_(buffer, num_comments_len);
+
+        if(block->num_comments == 0) {
+                block->comments = 0;
+        }
+        else if(0 == (block->comments = calloc(block->num_comments, sizeof(FLAC__StreamMetadata_VorbisComment_Entry))))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        for(i = 0; i < block->num_comments; i++) {
+                status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, block->comments + i, block_length);
+                if(block_length >= 4) block_length -= 4;
+                if(status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA) {
+                        block->num_comments = i;
+                        goto skip;
+                }
+                else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK) return status;
+                block_length -= block->comments[i].length;
+        }
+
+  skip:
+        if(block_length > 0) {
+                /* bad metadata */
+                if(0 != seek_cb(handle, block_length, SEEK_CUR))
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track *track)
+{
+        unsigned i, len;
+        FLAC__byte buffer[32]; /* asserted below that this is big enough */
+
+        FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        track->offset = unpack_uint64_(buffer, len);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        track->number = (FLAC__byte)unpack_uint32_(buffer, len);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
+        if(read_cb(track->isrc, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+        FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
+        len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN == 1);
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN == 1);
+        track->type = buffer[0] >> 7;
+        track->pre_emphasis = (buffer[0] >> 6) & 1;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        track->num_indices = (FLAC__byte)unpack_uint32_(buffer, len);
+
+        if(track->num_indices == 0) {
+                track->indices = 0;
+        }
+        else if(0 == (track->indices = calloc(track->num_indices, sizeof(FLAC__StreamMetadata_CueSheet_Index))))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        for(i = 0; i < track->num_indices; i++) {
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
+                if(read_cb(buffer, 1, len, handle) != len)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                track->indices[i].offset = unpack_uint64_(buffer, len);
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
+                if(read_cb(buffer, 1, len, handle) != len)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                track->indices[i].number = (FLAC__byte)unpack_uint32_(buffer, len);
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
+                if(read_cb(buffer, 1, len, handle) != len)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet *block)
+{
+        unsigned i, len;
+        FLAC__Metadata_SimpleIteratorStatus status;
+        FLAC__byte buffer[1024]; /* MSVC needs a constant expression so we put a magic number and assert */
+
+        FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN)/8 <= sizeof(buffer));
+        FLAC__ASSERT(sizeof(FLAC__uint64) <= sizeof(buffer));
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
+        if(read_cb(block->media_catalog_number, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->lead_in = unpack_uint64_(buffer, len);
+
+        FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
+        len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->is_cd = buffer[0]&0x80? true : false;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->num_tracks = unpack_uint32_(buffer, len);
+
+        if(block->num_tracks == 0) {
+                block->tracks = 0;
+        }
+        else if(0 == (block->tracks = calloc(block->num_tracks, sizeof(FLAC__StreamMetadata_CueSheet_Track))))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        for(i = 0; i < block->num_tracks; i++) {
+                if(FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = read_metadata_block_data_cuesheet_track_cb_(handle, read_cb, block->tracks + i)))
+                        return status;
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cstring_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__byte **data, FLAC__uint32 *length, FLAC__uint32 length_len)
+{
+        FLAC__byte buffer[sizeof(FLAC__uint32)];
+
+        FLAC__ASSERT(0 != data);
+        FLAC__ASSERT(length_len%8 == 0);
+
+        length_len /= 8; /* convert to bytes */
+
+        FLAC__ASSERT(sizeof(buffer) >= length_len);
+
+        if(read_cb(buffer, 1, length_len, handle) != length_len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        *length = unpack_uint32_(buffer, length_len);
+
+        if(0 != *data)
+                free(*data);
+
+        if(0 == (*data = safe_malloc_add_2op_(*length, /*+*/1)))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        if(*length > 0) {
+                if(read_cb(*data, 1, *length, handle) != *length)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        }
+
+        (*data)[*length] = '\0';
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture *block)
+{
+        FLAC__Metadata_SimpleIteratorStatus status;
+        FLAC__byte buffer[4]; /* asserted below that this is big enough */
+        FLAC__uint32 len;
+
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_TYPE_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->type = (FLAC__StreamMetadata_Picture_Type)unpack_uint32_(buffer, len);
+
+        if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, (FLAC__byte**)(&(block->mime_type)), &len, FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
+                return status;
+
+        if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->description), &len, FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
+                return status;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->width = unpack_uint32_(buffer, len);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->height = unpack_uint32_(buffer, len);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->depth = unpack_uint32_(buffer, len);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_COLORS_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8;
+        if(read_cb(buffer, 1, len, handle) != len)
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        block->colors = unpack_uint32_(buffer, len);
+
+        /* for convenience we use read_metadata_block_data_picture_cstring_cb_() even though it adds an extra terminating NUL we don't use */
+        if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->data), &(block->data_length), FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
+                return status;
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown *block, unsigned block_length)
+{
+        if(block_length == 0) {
+                block->data = 0;
+        }
+        else {
+                if(0 == (block->data = malloc(block_length)))
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+                if(read_cb(block->data, 1, block_length, handle) != block_length)
+                        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+        }
+
+        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+}
+
+FLAC__bool write_metadata_block_header_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block)
+{
+        FLAC__ASSERT(0 != file);
+        FLAC__ASSERT(0 != status);
+
+        if(!write_metadata_block_header_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block)) {
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                return false;
+        }
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block)
+{
+        FLAC__ASSERT(0 != file);
+        FLAC__ASSERT(0 != status);
+
+        if (write_metadata_block_data_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block)) {
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
+                return true;
+        }
+        else {
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                return false;
+        }
+}
+
+FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block)
+{
+        FLAC__byte buffer[FLAC__STREAM_METADATA_HEADER_LENGTH];
+
+        FLAC__ASSERT(block->length < (1u << FLAC__STREAM_METADATA_LENGTH_LEN));
+
+        buffer[0] = (block->is_last? 0x80 : 0) | (FLAC__byte)block->type;
+        pack_uint32_(block->length, buffer + 1, 3);
+
+        if(write_cb(buffer, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block)
+{
+        FLAC__ASSERT(0 != block);
+
+        switch(block->type) {
+                case FLAC__METADATA_TYPE_STREAMINFO:
+                        return write_metadata_block_data_streaminfo_cb_(handle, write_cb, &block->data.stream_info);
+                case FLAC__METADATA_TYPE_PADDING:
+                        return write_metadata_block_data_padding_cb_(handle, write_cb, &block->data.padding, block->length);
+                case FLAC__METADATA_TYPE_APPLICATION:
+                        return write_metadata_block_data_application_cb_(handle, write_cb, &block->data.application, block->length);
+                case FLAC__METADATA_TYPE_SEEKTABLE:
+                        return write_metadata_block_data_seektable_cb_(handle, write_cb, &block->data.seek_table);
+                case FLAC__METADATA_TYPE_VORBIS_COMMENT:
+                        return write_metadata_block_data_vorbis_comment_cb_(handle, write_cb, &block->data.vorbis_comment);
+                case FLAC__METADATA_TYPE_CUESHEET:
+                        return write_metadata_block_data_cuesheet_cb_(handle, write_cb, &block->data.cue_sheet);
+                case FLAC__METADATA_TYPE_PICTURE:
+                        return write_metadata_block_data_picture_cb_(handle, write_cb, &block->data.picture);
+                default:
+                        return write_metadata_block_data_unknown_cb_(handle, write_cb, &block->data.unknown, block->length);
+        }
+}
+
+FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo *block)
+{
+        FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH];
+        const unsigned channels1 = block->channels - 1;
+        const unsigned bps1 = block->bits_per_sample - 1;
+
+        /* we are using hardcoded numbers for simplicity but we should
+         * probably eventually write a bit-level packer and use the
+         * _STREAMINFO_ constants.
+         */
+        pack_uint32_(block->min_blocksize, buffer, 2);
+        pack_uint32_(block->max_blocksize, buffer+2, 2);
+        pack_uint32_(block->min_framesize, buffer+4, 3);
+        pack_uint32_(block->max_framesize, buffer+7, 3);
+        buffer[10] = (block->sample_rate >> 12) & 0xff;
+        buffer[11] = (block->sample_rate >> 4) & 0xff;
+        buffer[12] = ((block->sample_rate & 0x0f) << 4) | (channels1 << 1) | (bps1 >> 4);
+        buffer[13] = (FLAC__byte)(((bps1 & 0x0f) << 4) | ((block->total_samples >> 32) & 0x0f));
+        pack_uint32_((FLAC__uint32)block->total_samples, buffer+14, 4);
+        memcpy(buffer+18, block->md5sum, 16);
+
+        if(write_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding *block, unsigned block_length)
+{
+        unsigned i, n = block_length;
+        FLAC__byte buffer[1024];
+
+        (void)block;
+
+        memset(buffer, 0, 1024);
+
+        for(i = 0; i < n/1024; i++)
+                if(write_cb(buffer, 1, 1024, handle) != 1024)
+                        return false;
+
+        n %= 1024;
+
+        if(write_cb(buffer, 1, n, handle) != n)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application *block, unsigned block_length)
+{
+        const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;
+
+        if(write_cb(block->id, 1, id_bytes, handle) != id_bytes)
+                return false;
+
+        block_length -= id_bytes;
+
+        if(write_cb(block->data, 1, block_length, handle) != block_length)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable *block)
+{
+        unsigned i;
+        FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];
+
+        for(i = 0; i < block->num_points; i++) {
+                /* some MAGIC NUMBERs here */
+                pack_uint64_(block->points[i].sample_number, buffer, 8);
+                pack_uint64_(block->points[i].stream_offset, buffer+8, 8);
+                pack_uint32_(block->points[i].frame_samples, buffer+16, 2);
+                if(write_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
+                        return false;
+        }
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment *block)
+{
+        unsigned i;
+        const unsigned entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
+        const unsigned num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
+        FLAC__byte buffer[4]; /* magic number is asserted below */
+
+        FLAC__ASSERT(flac_max(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN, FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN) / 8 == sizeof(buffer));
+
+        pack_uint32_little_endian_(block->vendor_string.length, buffer, entry_length_len);
+        if(write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
+                return false;
+        if(write_cb(block->vendor_string.entry, 1, block->vendor_string.length, handle) != block->vendor_string.length)
+                return false;
+
+        pack_uint32_little_endian_(block->num_comments, buffer, num_comments_len);
+        if(write_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
+                return false;
+
+        for(i = 0; i < block->num_comments; i++) {
+                pack_uint32_little_endian_(block->comments[i].length, buffer, entry_length_len);
+                if(write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
+                        return false;
+                if(write_cb(block->comments[i].entry, 1, block->comments[i].length, handle) != block->comments[i].length)
+                        return false;
+        }
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet *block)
+{
+        unsigned i, j, len;
+        FLAC__byte buffer[1024]; /* asserted below that this is big enough */
+
+        FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN)/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN/8);
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
+        if(write_cb(block->media_catalog_number, 1, len, handle) != len)
+                return false;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
+        pack_uint64_(block->lead_in, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
+        len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
+        memset(buffer, 0, len);
+        if(block->is_cd)
+                buffer[0] |= 0x80;
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
+        len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
+        pack_uint32_(block->num_tracks, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        for(i = 0; i < block->num_tracks; i++) {
+                FLAC__StreamMetadata_CueSheet_Track *track = block->tracks + i;
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
+                pack_uint64_(track->offset, buffer, len);
+                if(write_cb(buffer, 1, len, handle) != len)
+                        return false;
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
+                pack_uint32_(track->number, buffer, len);
+                if(write_cb(buffer, 1, len, handle) != len)
+                        return false;
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
+                if(write_cb(track->isrc, 1, len, handle) != len)
+                        return false;
+
+                FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
+                len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
+                memset(buffer, 0, len);
+                buffer[0] = (track->type << 7) | (track->pre_emphasis << 6);
+                if(write_cb(buffer, 1, len, handle) != len)
+                        return false;
+
+                FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
+                len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
+                pack_uint32_(track->num_indices, buffer, len);
+                if(write_cb(buffer, 1, len, handle) != len)
+                        return false;
+
+                for(j = 0; j < track->num_indices; j++) {
+                        FLAC__StreamMetadata_CueSheet_Index *indx = track->indices + j;
+
+                        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
+                        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
+                        pack_uint64_(indx->offset, buffer, len);
+                        if(write_cb(buffer, 1, len, handle) != len)
+                                return false;
+
+                        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
+                        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
+                        pack_uint32_(indx->number, buffer, len);
+                        if(write_cb(buffer, 1, len, handle) != len)
+                                return false;
+
+                        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
+                        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
+                        memset(buffer, 0, len);
+                        if(write_cb(buffer, 1, len, handle) != len)
+                                return false;
+                }
+        }
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture *block)
+{
+        unsigned len;
+        size_t slen;
+        FLAC__byte buffer[4]; /* magic number is asserted below */
+
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_TYPE_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_COLORS_LEN%8);
+        FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN%8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8);
+        FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN/8);
+
+        len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8;
+        pack_uint32_(block->type, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN/8;
+        slen = strlen(block->mime_type);
+        pack_uint32_(slen, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+        if(write_cb(block->mime_type, 1, slen, handle) != slen)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN/8;
+        slen = strlen((const char *)block->description);
+        pack_uint32_(slen, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+        if(write_cb(block->description, 1, slen, handle) != slen)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8;
+        pack_uint32_(block->width, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8;
+        pack_uint32_(block->height, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8;
+        pack_uint32_(block->depth, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8;
+        pack_uint32_(block->colors, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+
+        len = FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN/8;
+        pack_uint32_(block->data_length, buffer, len);
+        if(write_cb(buffer, 1, len, handle) != len)
+                return false;
+        if(write_cb(block->data, 1, block->data_length, handle) != block->data_length)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown *block, unsigned block_length)
+{
+        if(write_cb(block->data, 1, block_length, handle) != block_length)
+                return false;
+
+        return true;
+}
+
+FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator *iterator, const FLAC__StreamMetadata *block)
+{
+        if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        if(!write_metadata_block_header_(iterator->file, &iterator->status, block))
+                return false;
+
+        if(!write_metadata_block_data_(iterator->file, &iterator->status, block))
+                return false;
+
+        if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        return read_metadata_block_header_(iterator);
+}
+
+FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, unsigned padding_length, FLAC__bool padding_is_last)
+{
+        FLAC__StreamMetadata *padding;
+
+        if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        block->is_last = false;
+
+        if(!write_metadata_block_header_(iterator->file, &iterator->status, block))
+                return false;
+
+        if(!write_metadata_block_data_(iterator->file, &iterator->status, block))
+                return false;
+
+        if(0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING)))
+                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+
+        padding->is_last = padding_is_last;
+        padding->length = padding_length;
+
+        if(!write_metadata_block_header_(iterator->file, &iterator->status, padding)) {
+                FLAC__metadata_object_delete(padding);
+                return false;
+        }
+
+        if(!write_metadata_block_data_(iterator->file, &iterator->status, padding)) {
+                FLAC__metadata_object_delete(padding);
+                return false;
+        }
+
+        FLAC__metadata_object_delete(padding);
+
+        if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        return read_metadata_block_header_(iterator);
+}
+
+FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool append)
+{
+        FILE *tempfile = NULL;
+        char *tempfilename = NULL;
+        int fixup_is_last_code = 0; /* 0 => no need to change any is_last flags */
+        FLAC__off_t fixup_is_last_flag_offset = -1;
+
+        FLAC__ASSERT(0 != block || append == false);
+
+        if(iterator->is_last) {
+                if(append) {
+                        fixup_is_last_code = 1; /* 1 => clear the is_last flag at the following offset */
+                        fixup_is_last_flag_offset = iterator->offset[iterator->depth];
+                }
+                else if(0 == block) {
+                        simple_iterator_push_(iterator);
+                        if(!FLAC__metadata_simple_iterator_prev(iterator)) {
+                                (void)simple_iterator_pop_(iterator);
+                                return false;
+                        }
+                        fixup_is_last_code = -1; /* -1 => set the is_last the flag at the following offset */
+                        fixup_is_last_flag_offset = iterator->offset[iterator->depth];
+                        if(!simple_iterator_pop_(iterator))
+                                return false;
+                }
+        }
+
+        if(!simple_iterator_copy_file_prefix_(iterator, &tempfile, &tempfilename, append))
+                return false;
+
+        if(0 != block) {
+                if(!write_metadata_block_header_(tempfile, &iterator->status, block)) {
+                        cleanup_tempfile_(&tempfile, &tempfilename);
+                        return false;
+                }
+
+                if(!write_metadata_block_data_(tempfile, &iterator->status, block)) {
+                        cleanup_tempfile_(&tempfile, &tempfilename);
+                        return false;
+                }
+        }
+
+        if(!simple_iterator_copy_file_postfix_(iterator, &tempfile, &tempfilename, fixup_is_last_code, fixup_is_last_flag_offset, block==0))
+                return false;
+
+        if(append)
+                return FLAC__metadata_simple_iterator_next(iterator);
+
+        return true;
+}
+
+void simple_iterator_push_(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(iterator->depth+1 < SIMPLE_ITERATOR_MAX_PUSH_DEPTH);
+        iterator->offset[iterator->depth+1] = iterator->offset[iterator->depth];
+        iterator->depth++;
+}
+
+FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator *iterator)
+{
+        FLAC__ASSERT(iterator->depth > 0);
+        iterator->depth--;
+        if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+
+        return read_metadata_block_header_(iterator);
+}
+
+/* return meanings:
+ * 0: ok
+ * 1: read error
+ * 2: seek error
+ * 3: not a FLAC file
+ */
+unsigned seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb)
+{
+        FLAC__byte buffer[4];
+        size_t n;
+        unsigned i;
+
+        FLAC__ASSERT(FLAC__STREAM_SYNC_LENGTH == sizeof(buffer));
+
+        /* skip any id3v2 tag */
+        errno = 0;
+        n = read_cb(buffer, 1, 4, handle);
+        if(errno)
+                return 1;
+        else if(n != 4)
+                return 3;
+        else if(0 == memcmp(buffer, "ID3", 3)) {
+                unsigned tag_length = 0;
+
+                /* skip to the tag length */
+                if(seek_cb(handle, 2, SEEK_CUR) < 0)
+                        return 2;
+
+                /* read the length */
+                for(i = 0; i < 4; i++) {
+                        if(read_cb(buffer, 1, 1, handle) < 1 || buffer[0] & 0x80)
+                                return 1;
+                        tag_length <<= 7;
+                        tag_length |= (buffer[0] & 0x7f);
+                }
+
+                /* skip the rest of the tag */
+                if(seek_cb(handle, tag_length, SEEK_CUR) < 0)
+                        return 2;
+
+                /* read the stream sync code */
+                errno = 0;
+                n = read_cb(buffer, 1, 4, handle);
+                if(errno)
+                        return 1;
+                else if(n != 4)
+                        return 3;
+        }
+
+        /* check for the fLaC signature */
+        if(0 == memcmp(FLAC__STREAM_SYNC_STRING, buffer, FLAC__STREAM_SYNC_LENGTH))
+                return 0;
+        else
+                return 3;
+}
+
+unsigned seek_to_first_metadata_block_(FILE *f)
+{
+        return seek_to_first_metadata_block_cb_((FLAC__IOHandle)f, (FLAC__IOCallback_Read)fread, fseek_wrapper_);
+}
+
+FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, FLAC__bool append)
+{
+        const FLAC__off_t offset_end = append? iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length : iterator->offset[iterator->depth];
+
+        if(0 != fseeko(iterator->file, 0, SEEK_SET)) {
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+        if(!open_tempfile_(iterator->filename, iterator->tempfile_path_prefix, tempfile, tempfilename, &iterator->status)) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                return false;
+        }
+        if(!copy_n_bytes_from_file_(iterator->file, *tempfile, offset_end, &iterator->status)) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                return false;
+        }
+
+        return true;
+}
+
+FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, int fixup_is_last_code, FLAC__off_t fixup_is_last_flag_offset, FLAC__bool backup)
+{
+        FLAC__off_t save_offset = iterator->offset[iterator->depth];
+        FLAC__ASSERT(0 != *tempfile);
+
+        if(0 != fseeko(iterator->file, save_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length, SEEK_SET)) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                return false;
+        }
+        if(!copy_remaining_bytes_from_file_(iterator->file, *tempfile, &iterator->status)) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                return false;
+        }
+
+        if(fixup_is_last_code != 0) {
+                /*
+                 * if code == 1, it means a block was appended to the end so
+                 *   we have to clear the is_last flag of the previous block
+                 * if code == -1, it means the last block was deleted so
+                 *   we have to set the is_last flag of the previous block
+                 */
+                /* MAGIC NUMBERs here; we know the is_last flag is the high bit of the byte at this location */
+                FLAC__byte x;
+                if(0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET)) {
+                        cleanup_tempfile_(tempfile, tempfilename);
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                        return false;
+                }
+                if(fread(&x, 1, 1, *tempfile) != 1) {
+                        cleanup_tempfile_(tempfile, tempfilename);
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                }
+                if(fixup_is_last_code > 0) {
+                        FLAC__ASSERT(x & 0x80);
+                        x &= 0x7f;
+                }
+                else {
+                        FLAC__ASSERT(!(x & 0x80));
+                        x |= 0x80;
+                }
+                if(0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET)) {
+                        cleanup_tempfile_(tempfile, tempfilename);
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
+                        return false;
+                }
+                if(local__fwrite(&x, 1, 1, *tempfile) != 1) {
+                        cleanup_tempfile_(tempfile, tempfilename);
+                        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                        return false;
+                }
+        }
+
+        (void)fclose(iterator->file);
+
+        if(!transport_tempfile_(iterator->filename, tempfile, tempfilename, &iterator->status))
+                return false;
+
+        if(iterator->has_stats)
+                set_file_stats_(iterator->filename, &iterator->stats);
+
+        if(!simple_iterator_prime_input_(iterator, !iterator->is_writable))
+                return false;
+        if(backup) {
+                while(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length < save_offset)
+                        if(!FLAC__metadata_simple_iterator_next(iterator))
+                                return false;
+                return true;
+        }
+        else {
+                /* move the iterator to it's original block faster by faking a push, then doing a pop_ */
+                FLAC__ASSERT(iterator->depth == 0);
+                iterator->offset[0] = save_offset;
+                iterator->depth++;
+                return simple_iterator_pop_(iterator);
+        }
+}
+
+FLAC__bool copy_n_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        FLAC__byte buffer[8192];
+        size_t n;
+
+        FLAC__ASSERT(bytes >= 0);
+        while(bytes > 0) {
+                n = flac_min(sizeof(buffer), (size_t)bytes);
+                if(fread(buffer, 1, n, file) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                }
+                if(local__fwrite(buffer, 1, n, tempfile) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                        return false;
+                }
+                bytes -= n;
+        }
+
+        return true;
+}
+
+FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        FLAC__byte buffer[8192];
+        size_t n;
+
+        FLAC__ASSERT(bytes >= 0);
+        while(bytes > 0) {
+                n = flac_min(sizeof(buffer), (size_t)bytes);
+                if(read_cb(buffer, 1, n, handle) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                }
+                if(temp_write_cb(buffer, 1, n, temp_handle) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                        return false;
+                }
+                bytes -= n;
+        }
+
+        return true;
+}
+
+FLAC__bool copy_remaining_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        FLAC__byte buffer[8192];
+        size_t n;
+
+        while(!feof(file)) {
+                n = fread(buffer, 1, sizeof(buffer), file);
+                if(n == 0 && !feof(file)) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                }
+                if(n > 0 && local__fwrite(buffer, 1, n, tempfile) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                        return false;
+                }
+        }
+
+        return true;
+}
+
+FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        FLAC__byte buffer[8192];
+        size_t n;
+
+        while(!eof_cb(handle)) {
+                n = read_cb(buffer, 1, sizeof(buffer), handle);
+                if(n == 0 && !eof_cb(handle)) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
+                        return false;
+                }
+                if(n > 0 && temp_write_cb(buffer, 1, n, temp_handle) != n) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
+                        return false;
+                }
+        }
+
+        return true;
+}
+
+static int
+local_snprintf(char *str, size_t size, const char *fmt, ...)
+{
+        va_list va;
+        int rc;
+
+        va_start (va, fmt);
+
+#if defined _MSC_VER
+        if (size == 0)
+                return 1024;
+        rc = vsnprintf_s (str, size, _TRUNCATE, fmt, va);
+        if (rc < 0)
+                rc = size - 1;
+#elif defined __MINGW32__
+        rc = __mingw_vsnprintf (str, size, fmt, va);
+#else
+        rc = vsnprintf (str, size, fmt, va);
+#endif
+        va_end (va);
+
+        return rc;
+}
+
+FLAC__bool open_tempfile_(const char *filename, const char *tempfile_path_prefix, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        static const char *tempfile_suffix = ".metadata_edit";
+        if(0 == tempfile_path_prefix) {
+                size_t dest_len = strlen(filename) + strlen(tempfile_suffix) + 1;
+                if(0 == (*tempfilename = safe_malloc_(dest_len))) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+                        return false;
+                }
+                local_snprintf(*tempfilename, dest_len, "%s%s", filename, tempfile_suffix);
+        }
+        else {
+                const char *p = strrchr(filename, '/');
+                size_t dest_len;
+                if(0 == p)
+                        p = filename;
+                else
+                        p++;
+
+                dest_len = strlen(tempfile_path_prefix) + strlen(p) + strlen(tempfile_suffix) + 2;
+
+                if(0 == (*tempfilename = safe_malloc_(dest_len))) {
+                        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
+                        return false;
+                }
+                local_snprintf(*tempfilename, dest_len, "%s/%s%s", tempfile_path_prefix, p, tempfile_suffix);
+        }
+
+        if(0 == (*tempfile = flac_fopen(*tempfilename, "w+b"))) {
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
+                return false;
+        }
+
+        return true;
+}
+
+FLAC__bool transport_tempfile_(const char *filename, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status)
+{
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != tempfile);
+        FLAC__ASSERT(0 != *tempfile);
+        FLAC__ASSERT(0 != tempfilename);
+        FLAC__ASSERT(0 != *tempfilename);
+        FLAC__ASSERT(0 != status);
+
+        (void)fclose(*tempfile);
+        *tempfile = 0;
+
+#if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__ || defined __EMX__
+        /* on some flavors of windows, flac_rename() will fail if the destination already exists */
+        if(flac_unlink(filename) < 0) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR;
+                return false;
+        }
+#endif
+
+        /*@@@ to fully support the tempfile_path_prefix we need to update this piece to actually copy across filesystems instead of just flac_rename(): */
+        if(0 != flac_rename(*tempfilename, filename)) {
+                cleanup_tempfile_(tempfile, tempfilename);
+                *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR;
+                return false;
+        }
+
+        cleanup_tempfile_(tempfile, tempfilename);
+
+        return true;
+}
+
+void cleanup_tempfile_(FILE **tempfile, char **tempfilename)
+{
+        if(0 != *tempfile) {
+                (void)fclose(*tempfile);
+                *tempfile = 0;
+        }
+
+        if(0 != *tempfilename) {
+                (void)flac_unlink(*tempfilename);
+                free(*tempfilename);
+                *tempfilename = 0;
+        }
+}
+
+FLAC__bool get_file_stats_(const char *filename, struct flac_stat_s *stats)
+{
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != stats);
+        return (0 == flac_stat(filename, stats));
+}
+
+void set_file_stats_(const char *filename, struct flac_stat_s *stats)
+{
+        struct utimbuf srctime;
+
+        FLAC__ASSERT(0 != filename);
+        FLAC__ASSERT(0 != stats);
+
+        srctime.actime = stats->st_atime;
+        srctime.modtime = stats->st_mtime;
+        (void)flac_chmod(filename, stats->st_mode);
+        (void)flac_utime(filename, &srctime);
+#if !defined _MSC_VER && !defined __BORLANDC__ && !defined __MINGW32__
+        FLAC_CHECK_RETURN(chown(filename, stats->st_uid, -1));
+        FLAC_CHECK_RETURN(chown(filename, -1, stats->st_gid));
+#endif
+}
+
+int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
+{
+        return fseeko((FILE*)handle, (FLAC__off_t)offset, whence);
+}
+
+FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle)
+{
+        return ftello((FILE*)handle);
+}
+
+FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status)
+{
+        switch(status) {
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK:
+                        return FLAC__METADATA_CHAIN_STATUS_OK;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT:
+                        return FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE:
+                        return FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE:
+                        return FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE:
+                        return FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA:
+                        return FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR:
+                        return FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
+                case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR:
+                default:
+                        return FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
+        }
+}