Add ijar to third_party and use it for generating .jar.toc files in GN

third_party/ijar/zip.cc

+// Copyright 2007 Alan Donovan. All rights reserved.
+//
+// Author: Alan Donovan <adonovan@google.com>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// zip.cc -- .zip (.jar) file reading/writing routines.
+//
+
+// See README.txt for details.
+//
+// See http://www.pkware.com/documents/casestudies/APPNOTE.TXT
+// for definition of PKZIP file format.
+
+#define _FILE_OFFSET_BITS 64  // Support zip files larger than 2GB
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <limits.h>
+#include <limits>
+#include <vector>
+
+#include "third_party/ijar/zip.h"
+#include <zlib.h>
+
+#define LOCAL_FILE_HEADER_SIGNATURE           0x04034b50
+#define CENTRAL_FILE_HEADER_SIGNATURE         0x02014b50
+#define END_OF_CENTRAL_DIR_SIGNATURE          0x06054b50
+#define DATA_DESCRIPTOR_SIGNATURE             0x08074b50
+
+// version to extract: 1.0 - default value from APPNOTE.TXT.
+// Output JAR files contain no extra ZIP features, so this is enough.
+#define ZIP_VERSION_TO_EXTRACT                10
+#define COMPRESSION_METHOD_STORED             0   // no compression
+#define COMPRESSION_METHOD_DEFLATED           8
+
+#define GENERAL_PURPOSE_BIT_FLAG_COMPRESSED (1 << 3)
+#define GENERAL_PURPOSE_BIT_FLAG_UTF8_ENCODED (1 << 11)
+#define GENERAL_PURPOSE_BIT_FLAG_COMPRESSION_SPEED ((1 << 2) | (1 << 1))
+#define GENERAL_PURPOSE_BIT_FLAG_SUPPORTED \
+  (GENERAL_PURPOSE_BIT_FLAG_COMPRESSED \
+  | GENERAL_PURPOSE_BIT_FLAG_UTF8_ENCODED \
+  | GENERAL_PURPOSE_BIT_FLAG_COMPRESSION_SPEED)
+
+namespace devtools_ijar {
+// In the absence of ZIP64 support, zip files are limited to 4GB.
+// http://www.info-zip.org/FAQ.html#limits
+static const u8 kMaximumOutputSize = std::numeric_limits<uint32_t>::max();
+
+static bool ProcessCentralDirEntry(const u1 *&p,
+                                   size_t *compressed_size,
+                                   size_t *uncompressed_size,
+                                   char *filename,
+                                   size_t filename_size,
+                                   u4 *attr,
+                                   u4 *offset);
+
+//
+// A class representing a ZipFile for reading. Its public API is exposed
+// using the ZipExtractor abstract class.
+//
+class InputZipFile : public ZipExtractor {
+ public:
+  InputZipFile(ZipExtractorProcessor *processor, int fd, off_t in_length,
+               off_t in_offset, const u1* zipdata_in, const u1* central_dir);
+  virtual ~InputZipFile();
+
+  virtual const char* GetError() {
+    if (errmsg[0] == 0) {
+      return NULL;
+    }
+    return errmsg;
+  }
+
+  virtual bool ProcessNext();
+  virtual void Reset();
+  virtual size_t GetSize() {
+    return in_length_;
+  }
+
+  virtual u8 CalculateOutputLength();
+
+ private:
+  ZipExtractorProcessor *processor;
+
+  int fd_in;  // Input file descripor
+
+  // InputZipFile is responsible for maintaining the following
+  // pointers. They are allocated by the Create() method before
+  // the object is actually created using mmap.
+  const u1 * const zipdata_in_;   // start of input file mmap
+  const u1 * zipdata_in_mapped_;  // start of still mapped region
+  const u1 * const central_dir_;  // central directory in input file
+
+  size_t in_length_;  // size of the input file
+  size_t in_offset_;  // offset  the input file
+
+  const u1 *p;  // input cursor
+
+  const u1* central_dir_current_;  // central dir input cursor
+
+  // Buffer size is initially INITIAL_BUFFER_SIZE. It doubles in size every
+  // time it is found too small, until it reaches MAX_BUFFER_SIZE. If that is
+  // not enough, we bail out. We only decompress class files, so they should
+  // be smaller than 64K anyway, but we give a little leeway.
+  // MAX_BUFFER_SIZE must be bigger than the size of the biggest file in the
+  // ZIP. It is set to 128M here so we can uncompress the Bazel server with
+  // this library.
+  static const size_t INITIAL_BUFFER_SIZE = 256 * 1024;  // 256K
+  static const size_t MAX_BUFFER_SIZE = 128 * 1024 * 1024;
+  static const size_t MAX_MAPPED_REGION = 32 * 1024 * 1024;
+
+  // These metadata fields are the fields of the ZIP header of the file being
+  // processed.
+  u2 extract_version_;
+  u2 general_purpose_bit_flag_;
+  u2 compression_method_;
+  u4 uncompressed_size_;
+  u4 compressed_size_;
+  u2 file_name_length_;
+  u2 extra_field_length_;
+  const u1 *file_name_;
+  const u1 *extra_field_;
+
+  // Administration of memory reserved for decompressed data. We use the same
+  // buffer for each file to avoid some malloc()/free() calls and free the
+  // memory only in the dtor. C-style memory management is used so that we
+  // can call realloc.
+  u1 *uncompressed_data_;
+  size_t uncompressed_data_allocated_;
+
+  // Copy of the last filename entry - Null-terminated.
+  char filename[PATH_MAX];
+  // The external file attribute field
+  u4 attr;
+
+  // last error
+  char errmsg[4*PATH_MAX];
+
+  int error(const char *fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    vsnprintf(errmsg, 4*PATH_MAX, fmt, ap);
+    va_end(ap);
+    return -1;
+  }
+
+  // Check that at least n bytes remain in the input file, otherwise
+  // abort with an error message.  "state" is the name of the field
+  // we're about to read, for diagnostics.
+  int EnsureRemaining(size_t n, const char *state) {
+    size_t in_offset = p - zipdata_in_;
+    size_t remaining = in_length_ - in_offset;
+    if (n > remaining) {
+      return error("Premature end of file (at offset %zd, state=%s); "
+                   "expected %zd more bytes but found %zd.\n",
+                   in_offset, state, n, remaining);
+    }
+    return 0;
+  }
+
+  // Read one entry from input zip file
+  int ProcessLocalFileEntry(size_t compressed_size, size_t uncompressed_size);
+
+  // Uncompress a file from the archive using zlib. The pointer returned
+  // is owned by InputZipFile, so it must not be freed. Advances the input
+  // cursor to the first byte after the compressed data.
+  u1* UncompressFile();
+
+  // Skip a file
+  int SkipFile(const bool compressed);
+
+  // Process a file
+  int ProcessFile(const bool compressed);
+};
+
+//
+// A class implementing ZipBuilder that represent an open zip file for writing.
+//
+class OutputZipFile : public ZipBuilder {
+ public:
+  OutputZipFile(int fd, u1 * const zipdata_out) :
+      fd_out(fd),
+      zipdata_out_(zipdata_out),
+      q(zipdata_out) {
+    errmsg[0] = 0;
+  }
+
+  virtual const char* GetError() {
+    if (errmsg[0] == 0) {
+      return NULL;
+    }
+    return errmsg;
+  }
+
+  virtual ~OutputZipFile() { Finish(); }
+  virtual u1* NewFile(const char* filename, const u4 attr);
+  virtual int FinishFile(size_t filelength, bool compress = false);
+  virtual int WriteEmptyFile(const char *filename);
+  virtual size_t GetSize() {
+    return Offset(q);
+  }
+  virtual int GetNumberFiles() {
+    return entries_.size();
+  }
+  virtual int Finish();
+
+ private:
+  struct LocalFileEntry {
+    // Start of the local header (in the output buffer).
+    size_t local_header_offset;
+
+    // Sizes of the file entry
+    size_t uncompressed_length;
+    size_t compressed_length;
+
+    // Compression method
+    u2 compression_method;
+
+    // external attributes field
+    u4 external_attr;
+
+    // Start/length of the file_name in the local header.
+    u1 *file_name;
+    u2 file_name_length;
+
+    // Start/length of the extra_field in the local header.
+    const u1 *extra_field;
+    u2 extra_field_length;
+  };
+
+  int fd_out;  // file descriptor for the output file
+
+  // OutputZipFile is responsible for maintaining the following
+  // pointers. They are allocated by the Create() method before
+  // the object is actually created using mmap.
+  u1 * const zipdata_out_;        // start of output file mmap
+  u1 *q;  // output cursor
+
+  u1 *header_ptr;  // Current pointer to "compression method" entry.
+
+  // List of entries to write the central directory
+  std::vector<LocalFileEntry*> entries_;
+
+  // last error
+  char errmsg[4*PATH_MAX];
+
+  int error(const char *fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    vsnprintf(errmsg, 4*PATH_MAX, fmt, ap);
+    va_end(ap);
+    return -1;
+  }
+
+  // Write the ZIP central directory structure for each local file
+  // entry in "entries".
+  void WriteCentralDirectory();
+
+  // Returns the offset of the pointer relative to the start of the
+  // output zip file.
+  size_t Offset(const u1 *const x) {
+    return x - zipdata_out_;
+  }
+
+  // Write ZIP file header in the output. Since the compressed size is not
+  // known in advance, it must be recorded later. This method returns a pointer
+  // to "compressed size" in the file header that should be passed to
+  // WriteFileSizeInLocalFileHeader() later.
+  u1* WriteLocalFileHeader(const char *filename, const u4 attr);
+
+  // Fill in the "compressed size" and "uncompressed size" fields in a local
+  // file header previously written by WriteLocalFileHeader().
+  size_t WriteFileSizeInLocalFileHeader(u1 *header_ptr, size_t out_length,
+                                        bool compress = false);
+};
+
+//
+// Implementation of InputZipFile
+//
+bool InputZipFile::ProcessNext() {
+  // Process the next entry in the central directory. Also make sure that the
+  // content pointer is in sync.
+  size_t compressed, uncompressed;
+  u4 offset;
+  if (!ProcessCentralDirEntry(central_dir_current_, &compressed, &uncompressed,
+                              filename, PATH_MAX, &attr, &offset)) {
+    return false;
+  }
+
+  // There might be an offset specified in the central directory that does
+  // not match the file offset, if so, correct the pointer.
+  if (offset != 0 && (p != (zipdata_in_ + in_offset_ + offset))) {
+    p = zipdata_in_ + offset;
+  }
+
+  if (EnsureRemaining(4, "signature") < 0) {
+    return false;
+  }
+  u4 signature = get_u4le(p);
+  if (signature == LOCAL_FILE_HEADER_SIGNATURE) {
+    if (ProcessLocalFileEntry(compressed, uncompressed) < 0) {
+      return false;
+    }
+  } else {
+    error("local file header signature for file %s not found\n", filename);
+    return false;
+  }
+
+  return true;
+}
+
+int InputZipFile::ProcessLocalFileEntry(
+    size_t compressed_size, size_t uncompressed_size) {
+  if (EnsureRemaining(26, "extract_version") < 0) {
+    return -1;
+  }
+  extract_version_ = get_u2le(p);
+  general_purpose_bit_flag_ = get_u2le(p);
+
+  if ((general_purpose_bit_flag_ & ~GENERAL_PURPOSE_BIT_FLAG_SUPPORTED) != 0) {
+    return error("Unsupported value (0x%04x) in general purpose bit flag.\n",
+                 general_purpose_bit_flag_);
+  }
+
+  compression_method_ = get_u2le(p);
+
+  if (compression_method_ != COMPRESSION_METHOD_DEFLATED &&
+      compression_method_ != COMPRESSION_METHOD_STORED) {
+    return error("Unsupported compression method (%d).\n",
+                 compression_method_);
+  }
+
+  // skip over: last_mod_file_time, last_mod_file_date, crc32
+  p += 2 + 2 + 4;
+  compressed_size_ = get_u4le(p);
+  uncompressed_size_ = get_u4le(p);
+  file_name_length_ = get_u2le(p);
+  extra_field_length_ = get_u2le(p);
+
+  if (EnsureRemaining(file_name_length_, "file_name") < 0) {
+    return -1;
+  }
+  file_name_ = p;
+  p += file_name_length_;
+
+  if (EnsureRemaining(extra_field_length_, "extra_field") < 0) {
+    return -1;
+  }
+  extra_field_ = p;
+  p += extra_field_length_;
+
+  bool is_compressed = compression_method_ == COMPRESSION_METHOD_DEFLATED;
+
+  // If the zip is compressed, compressed and uncompressed size members are
+  // zero in the local file header. If not, check that they are the same as the
+  // lengths from the central directory, otherwise, just believe the central
+  // directory
+  if (compressed_size_ == 0) {
+    compressed_size_ = compressed_size;
+  } else {
+    if (compressed_size_ != compressed_size) {
+      return error("central directory and file header inconsistent\n");
+    }
+  }
+
+  if (uncompressed_size_ == 0) {
+    uncompressed_size_ = uncompressed_size;
+  } else {
+    if (uncompressed_size_ != uncompressed_size) {
+      return error("central directory and file header inconsistent\n");
+    }
+  }
+
+  if (processor->Accept(filename, attr)) {
+    if (ProcessFile(is_compressed) < 0) {
+      return -1;
+    }
+  } else {
+    if (SkipFile(is_compressed) < 0) {
+      return -1;
+    }
+  }
+
+  if (general_purpose_bit_flag_ & GENERAL_PURPOSE_BIT_FLAG_COMPRESSED) {
+    // Skip the data descriptor. Some implementations do not put the signature
+    // here, so check if the next 4 bytes are a signature, and if so, skip the
+    // next 12 bytes (for CRC, compressed/uncompressed size), otherwise skip
+    // the next 8 bytes (because the value just read was the CRC).
+    u4 signature = get_u4le(p);
+    if (signature == DATA_DESCRIPTOR_SIGNATURE) {
+      p += 4 * 3;
+    } else {
+      p += 4 * 2;
+    }
+  }
+
+  if (p > zipdata_in_mapped_ + MAX_MAPPED_REGION) {
+    munmap(const_cast<u1 *>(zipdata_in_mapped_), MAX_MAPPED_REGION);
+    zipdata_in_mapped_ += MAX_MAPPED_REGION;
+  }
+
+  return 0;
+}
+
+int InputZipFile::SkipFile(const bool compressed) {
+  if (!compressed) {
+    // In this case, compressed_size_ == uncompressed_size_ (since the file is
+    // uncompressed), so we can use either.
+    if (compressed_size_ != uncompressed_size_) {
+      return error("compressed size != uncompressed size, although the file "
+                   "is uncompressed.\n");
+    }
+  }
+
+  if (EnsureRemaining(compressed_size_, "file_data") < 0) {
+    return -1;
+  }
+  p += compressed_size_;
+  return 0;
+}
+
+u1* InputZipFile::UncompressFile() {
+  size_t in_offset = p - zipdata_in_;
+  size_t remaining = in_length_ - in_offset;
+  z_stream stream;
+
+  stream.zalloc = Z_NULL;
+  stream.zfree = Z_NULL;
+  stream.opaque = Z_NULL;
+  stream.avail_in = remaining;
+  stream.next_in = (Bytef *) p;
+
+  int ret = inflateInit2(&stream, -MAX_WBITS);
+  if (ret != Z_OK) {
+    error("inflateInit: %d\n", ret);
+    return NULL;
+  }
+
+  int uncompressed_until_now = 0;
+
+  while (true) {
+    stream.avail_out = uncompressed_data_allocated_ - uncompressed_until_now;
+    stream.next_out = uncompressed_data_ + uncompressed_until_now;
+    int old_avail_out = stream.avail_out;
+
+    ret = inflate(&stream, Z_SYNC_FLUSH);
+    int uncompressed_now = old_avail_out - stream.avail_out;
+    uncompressed_until_now += uncompressed_now;
+
+    switch (ret) {
+      case Z_STREAM_END: {
+        // zlib said that there is no more data to decompress.
+
+        u1 *new_p = reinterpret_cast<u1*>(stream.next_in);
+        compressed_size_ = new_p - p;
+        uncompressed_size_ = uncompressed_until_now;
+        p = new_p;
+        inflateEnd(&stream);
+        return uncompressed_data_;
+      }
+
+      case Z_OK: {
+        // zlib said that there is no more room in the buffer allocated for
+        // the decompressed data. Enlarge that buffer and try again.
+
+        if (uncompressed_data_allocated_ == MAX_BUFFER_SIZE) {
+          error("ijar does not support decompressing files "
+                "larger than %dMB.\n",
+                (int) (MAX_BUFFER_SIZE/(1024*1024)));
+          return NULL;
+        }
+
+        uncompressed_data_allocated_ *= 2;
+        if (uncompressed_data_allocated_ > MAX_BUFFER_SIZE) {
+          uncompressed_data_allocated_ = MAX_BUFFER_SIZE;
+        }
+
+        uncompressed_data_ = reinterpret_cast<u1*>(
+            realloc(uncompressed_data_, uncompressed_data_allocated_));
+        break;
+      }
+
+      case Z_DATA_ERROR:
+      case Z_BUF_ERROR:
+      case Z_STREAM_ERROR:
+      case Z_NEED_DICT:
+      default: {
+        error("zlib returned error code %d during inflate.\n", ret);
+        return NULL;
+      }
+    }
+  }
+}
+
+int InputZipFile::ProcessFile(const bool compressed) {
+  const u1 *file_data;
+  if (compressed) {
+    file_data = UncompressFile();
+    if (file_data == NULL) {
+      return -1;
+    }
+  } else {
+    // In this case, compressed_size_ == uncompressed_size_ (since the file is
+    // uncompressed), so we can use either.
+    if (compressed_size_ != uncompressed_size_) {
+      return error("compressed size != uncompressed size, although the file "
+                   "is uncompressed.\n");
+    }
+
+    if (EnsureRemaining(compressed_size_, "file_data") < 0) {
+      return -1;
+    }
+    file_data = p;
+    p += compressed_size_;
+  }
+  processor->Process(filename, attr, file_data, uncompressed_size_);
+  return 0;
+}
+
+
+// Reads and returns some metadata of the next file from the central directory:
+// - compressed size
+// - uncompressed size
+// - whether the entry is a class file (to be included in the output).
+// Precondition: p points to the beginning of an entry in the central dir
+// Postcondition: p points to the beginning of the next entry in the central dir
+// Returns true if the central directory contains another file and false if not.
+// Of course, in the latter case, the size output variables are not changed.
+// Note that the central directory is always followed by another data structure
+// that has a signature, so parsing it this way is safe.
+static bool ProcessCentralDirEntry(
+    const u1 *&p, size_t *compressed_size, size_t *uncompressed_size,
+    char *filename, size_t filename_size, u4 *attr, u4 *offset) {
+  u4 signature = get_u4le(p);
+  if (signature != CENTRAL_FILE_HEADER_SIGNATURE) {
+    return false;
+  }
+
+  p += 16;  // skip to 'compressed size' field
+  *compressed_size = get_u4le(p);
+  *uncompressed_size = get_u4le(p);
+  u2 file_name_length = get_u2le(p);
+  u2 extra_field_length = get_u2le(p);
+  u2 file_comment_length = get_u2le(p);
+  p += 4;  // skip to external file attributes field
+  *attr = get_u4le(p);
+  *offset = get_u4le(p);
+  {
+    size_t len = (file_name_length < filename_size)
+      ? file_name_length
+      : (filename_size - 1);
+    memcpy(reinterpret_cast<void*>(filename), p, len);
+    filename[len] = 0;
+  }
+  p += file_name_length;
+  p += extra_field_length;
+  p += file_comment_length;
+  return true;
+}
+
+// Gives a maximum bound on the size of the interface JAR. Basically, adds
+// the difference between the compressed and uncompressed sizes to the size
+// of the input file.
+u8 InputZipFile::CalculateOutputLength() {
+  const u1* current = central_dir_;
+
+  u8 compressed_size = 0;
+  u8 uncompressed_size = 0;
+  u8 skipped_compressed_size = 0;
+  u4 attr;
+  u4 offset;
+  char filename[PATH_MAX];
+
+  while (true) {
+    size_t file_compressed, file_uncompressed;
+    if (!ProcessCentralDirEntry(current,
+                                &file_compressed, &file_uncompressed,
+                                filename, PATH_MAX, &attr, &offset)) {
+      break;
+    }
+
+    if (processor->Accept(filename, attr)) {
+      compressed_size += (u8) file_compressed;
+      uncompressed_size += (u8) file_uncompressed;
+    } else {
+      skipped_compressed_size += file_compressed;
+    }
+  }
+
+  // The worst case is when the output is simply the input uncompressed. The
+  // metadata in the zip file will stay the same, so the file will grow by the
+  // difference between the compressed and uncompressed sizes.
+  return (u8) in_length_ - skipped_compressed_size
+      + (uncompressed_size - compressed_size);
+}
+
+// Given the data in the zip file, returns the offset of the central directory
+// and the number of files contained in it.
+bool FindZipCentralDirectory(const u1* bytes, size_t in_length,
+                             u4* offset, const u1** central_dir) {
+  static const int MAX_COMMENT_LENGTH = 0xffff;
+  static const int CENTRAL_DIR_LOCATOR_SIZE = 22;
+  // Maximum distance of start of central dir locator from end of file
+  static const int MAX_DELTA = MAX_COMMENT_LENGTH + CENTRAL_DIR_LOCATOR_SIZE;
+  const u1* last_pos_to_check = in_length < MAX_DELTA
+      ? bytes
+      : bytes + (in_length - MAX_DELTA);
+  const u1* current;
+  bool found = false;
+
+  for (current = bytes + in_length - CENTRAL_DIR_LOCATOR_SIZE;
+       current >= last_pos_to_check;
+       current-- ) {
+    const u1* p = current;
+    if (get_u4le(p) != END_OF_CENTRAL_DIR_SIGNATURE) {
+      continue;
+    }
+
+    p += 16;  // skip to comment length field
+    u2 comment_length = get_u2le(p);
+
+    // Does the comment go exactly till the end of the file?
+    if (current + comment_length + CENTRAL_DIR_LOCATOR_SIZE
+        != bytes + in_length) {
+      continue;
+    }
+
+    // Hooray, we found it!
+    found = true;
+    break;
+  }
+
+  if (!found) {
+    fprintf(stderr, "file is invalid or corrupted (missing end of central "
+                    "directory record)\n");
+    return false;
+  }
+
+  const u1* end_of_central_dir = current;
+  get_u4le(current);  // central directory locator signature, already checked
+  u2 number_of_this_disk = get_u2le(current);
+  u2 disk_with_central_dir = get_u2le(current);
+  u2 central_dir_entries_on_this_disk = get_u2le(current);
+  u2 central_dir_entries = get_u2le(current);
+  u4 central_dir_size = get_u4le(current);
+  u4 central_dir_offset = get_u4le(current);
+  u2 file_comment_length = get_u2le(current);
+  current += file_comment_length;  // set current to the end of the central dir
+
+  if (number_of_this_disk != 0
+    || disk_with_central_dir != 0
+    || central_dir_entries_on_this_disk != central_dir_entries) {
+    fprintf(stderr, "multi-disk JAR files are not supported\n");
+    return false;
+  }
+
+  // Do not change output values before determining that they are OK.
+  *offset = central_dir_offset;
+  // Central directory start can then be used to determine the actual
+  // starts of the zip file (which can be different in case of a non-zip
+  // header like for auto-extractable binaries).
+  *central_dir = end_of_central_dir - central_dir_size;
+  return true;
+}
+
+void InputZipFile::Reset() {
+  central_dir_current_ = central_dir_;
+  zipdata_in_mapped_ = zipdata_in_;
+  p = zipdata_in_ + in_offset_;
+}
+
+int ZipExtractor::ProcessAll() {
+  while (ProcessNext()) {}
+  if (GetError() != NULL) {
+    return -1;
+  }
+  return 0;
+}
+
+ZipExtractor* ZipExtractor::Create(const char* filename,
+                                   ZipExtractorProcessor *processor) {
+  int fd_in = open(filename, O_RDONLY);
+  if (fd_in < 0) {
+    return NULL;
+  }
+
+  off_t length = lseek(fd_in, 0, SEEK_END);
+  if (length < 0) {
+    return NULL;
+  }
+
+  void *zipdata_in = mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd_in, 0);
+  if (zipdata_in == MAP_FAILED) {
+    return NULL;
+  }
+
+  u4 central_dir_offset;
+  const u1 *central_dir = NULL;
+
+  if (!devtools_ijar::FindZipCentralDirectory(
+          static_cast<const u1*>(zipdata_in), length,
+          &central_dir_offset, &central_dir)) {
+    errno = EIO;  // we don't really have a good error number
+    return NULL;
+  }
+  const u1 *zipdata_start = static_cast<const u1*>(zipdata_in);
+  off_t offset = - static_cast<off_t>(zipdata_start
+                                      + central_dir_offset
+                                      - central_dir);
+
+  return new InputZipFile(processor, fd_in, length, offset,
+                          zipdata_start, central_dir);
+}
+
+InputZipFile::InputZipFile(ZipExtractorProcessor *processor, int fd,
+                           off_t in_length, off_t in_offset,
+                           const u1* zipdata_in, const u1* central_dir)
+  : processor(processor), fd_in(fd),
+    zipdata_in_(zipdata_in), zipdata_in_mapped_(zipdata_in),
+    central_dir_(central_dir), in_length_(in_length), in_offset_(in_offset),
+    p(zipdata_in + in_offset), central_dir_current_(central_dir) {
+  uncompressed_data_allocated_ = INITIAL_BUFFER_SIZE;
+  uncompressed_data_ =
+    reinterpret_cast<u1*>(malloc(uncompressed_data_allocated_));
+  errmsg[0] = 0;
+}
+
+InputZipFile::~InputZipFile() {
+  free(uncompressed_data_);
+  close(fd_in);
+}
+
+
+//
+// Implementation of OutputZipFile
+//
+int OutputZipFile::WriteEmptyFile(const char *filename) {
+  const u1* file_name = (const u1*) filename;
+  size_t file_name_length = strlen(filename);
+
+  LocalFileEntry *entry = new LocalFileEntry;
+  entry->local_header_offset = Offset(q);
+  entry->external_attr = 0;
+
+  // Output the ZIP local_file_header:
+  put_u4le(q, LOCAL_FILE_HEADER_SIGNATURE);
+  put_u2le(q, 10);  // extract_version
+  put_u2le(q, 0);  // general_purpose_bit_flag
+  put_u2le(q, 0);  // compression_method
+  put_u2le(q, 0);  // last_mod_file_time
+  put_u2le(q, 0);  // last_mod_file_date
+  put_u4le(q, 0);  // crc32
+  put_u4le(q, 0);  // compressed_size
+  put_u4le(q, 0);  // uncompressed_size
+  put_u2le(q, file_name_length);
+  put_u2le(q, 0);  // extra_field_length
+  put_n(q, file_name, file_name_length);
+
+  entry->file_name_length = file_name_length;
+  entry->extra_field_length = 0;
+  entry->compressed_length = 0;
+  entry->uncompressed_length = 0;
+  entry->compression_method = 0;
+  entry->extra_field = (const u1 *)"";
+  entry->file_name = (u1*) strdup((const char *) file_name);
+  entries_.push_back(entry);
+
+  return 0;
+}
+
+void OutputZipFile::WriteCentralDirectory() {
+  // central directory:
+  const u1 *central_directory_start = q;
+  for (size_t ii = 0; ii < entries_.size(); ++ii) {
+    LocalFileEntry *entry = entries_[ii];
+    put_u4le(q, CENTRAL_FILE_HEADER_SIGNATURE);
+    put_u2le(q, 0);  // version made by
+
+    put_u2le(q, ZIP_VERSION_TO_EXTRACT);  // version to extract
+    put_u2le(q, 0);  // general purpose bit flag
+    put_u2le(q, entry->compression_method);  // compression method:
+    put_u2le(q, 0);                          // last_mod_file_time
+    put_u2le(q, 0);  // last_mod_file_date
+    put_u4le(q, 0);  // crc32 (jar/javac tools don't care)
+    put_u4le(q, entry->compressed_length);    // compressed_size
+    put_u4le(q, entry->uncompressed_length);  // uncompressed_size
+    put_u2le(q, entry->file_name_length);
+    put_u2le(q, entry->extra_field_length);
+
+    put_u2le(q, 0);  // file comment length
+    put_u2le(q, 0);  // disk number start
+    put_u2le(q, 0);  // internal file attributes
+    put_u4le(q, entry->external_attr);  // external file attributes
+    // relative offset of local header:
+    put_u4le(q, entry->local_header_offset);
+
+    put_n(q, entry->file_name, entry->file_name_length);
+    put_n(q, entry->extra_field, entry->extra_field_length);
+  }
+  u4 central_directory_size = q - central_directory_start;
+
+  put_u4le(q, END_OF_CENTRAL_DIR_SIGNATURE);
+  put_u2le(q, 0);  // number of this disk
+  put_u2le(q, 0);  // number of the disk with the start of the central directory
+  put_u2le(q, entries_.size());  // # central dir entries on this disk
+  put_u2le(q, entries_.size());  // total # entries in the central directory
+  put_u4le(q, central_directory_size);  // size of the central directory
+  put_u4le(q, Offset(central_directory_start));  // offset of start of central
+                                                 // directory wrt starting disk
+  put_u2le(q, 0);  // .ZIP file comment length
+}
+
+u1* OutputZipFile::WriteLocalFileHeader(const char* filename, const u4 attr) {
+  off_t file_name_length_ = strlen(filename);
+  LocalFileEntry *entry = new LocalFileEntry;
+  entry->local_header_offset = Offset(q);
+  entry->file_name_length = file_name_length_;
+  entry->file_name = new u1[file_name_length_];
+  entry->external_attr = attr;
+  memcpy(entry->file_name, filename, file_name_length_);
+  entry->extra_field_length = 0;
+  entry->extra_field = (const u1 *)"";
+
+  // Output the ZIP local_file_header:
+  put_u4le(q, LOCAL_FILE_HEADER_SIGNATURE);
+  put_u2le(q, ZIP_VERSION_TO_EXTRACT);     // version to extract
+  put_u2le(q, 0);                          // general purpose bit flag
+  u1 *header_ptr = q;
+  put_u2le(q, COMPRESSION_METHOD_STORED);  // compression method = placeholder
+  put_u2le(q, 0);                          // last_mod_file_time
+  put_u2le(q, 0);                          // last_mod_file_date
+  put_u4le(q, 0);                          // crc32 (jar/javac tools don't care)
+  put_u4le(q, 0);  // compressed_size = placeholder
+  put_u4le(q, 0);  // uncompressed_size = placeholder
+  put_u2le(q, entry->file_name_length);
+  put_u2le(q, entry->extra_field_length);
+
+  put_n(q, entry->file_name, entry->file_name_length);
+  put_n(q, entry->extra_field, entry->extra_field_length);
+  entries_.push_back(entry);
+
+  return header_ptr;
+}
+
+// Try to compress a file entry in memory using the deflate algorithm.
+// It will compress buf (of size length) unless the compressed size is bigger
+// than the input size. The result will overwrite the content of buf and the
+// final size is returned.
+size_t TryDeflate(u1 *buf, size_t length) {
+  u1 *outbuf = reinterpret_cast<u1 *>(malloc(length));
+  z_stream stream;
+
+  // Initialize the z_stream strcut for reading from buf and wrinting in outbuf.
+  stream.zalloc = Z_NULL;
+  stream.zfree = Z_NULL;
+  stream.opaque = Z_NULL;
+  stream.total_in = length;
+  stream.avail_in = length;
+  stream.total_out = length;
+  stream.avail_out = length;
+  stream.next_in = buf;
+  stream.next_out = outbuf;
+
+  if (deflateInit(&stream, Z_DEFAULT_COMPRESSION) != Z_OK) {
+    // Failure to compress => return the buffer uncompressed
+    free(outbuf);
+    return length;
+  }
+
+  if (deflate(&stream, Z_FINISH) == Z_STREAM_END) {
+    // Compression successful and fits in outbuf, let's copy the result in buf.
+    length = stream.total_out;
+    memcpy(buf, outbuf, length);
+  }
+
+  deflateEnd(&stream);
+  free(outbuf);
+
+  // Return the length of the resulting buffer
+  return length;
+}
+
+size_t OutputZipFile::WriteFileSizeInLocalFileHeader(u1 *header_ptr,
+                                                     size_t out_length,
+                                                     bool compress) {
+  size_t compressed_size = out_length;
+  if (compress) {
+    compressed_size = TryDeflate(q, out_length);
+  }
+  // compression method
+  if (compressed_size < out_length) {
+    put_u2le(header_ptr, COMPRESSION_METHOD_DEFLATED);
+  } else {
+    put_u2le(header_ptr, COMPRESSION_METHOD_STORED);
+  }
+  header_ptr += 8;
+  put_u4le(header_ptr, compressed_size);  // compressed_size
+  put_u4le(header_ptr, out_length);       // uncompressed_size
+  return compressed_size;
+}
+
+int OutputZipFile::Finish() {
+  if (fd_out > 0) {
+    WriteCentralDirectory();
+    if (ftruncate(fd_out, GetSize()) < 0) {
+      return error("ftruncate(fd_out, GetSize()): %s", strerror(errno));
+    }
+    if (close(fd_out) < 0) {
+      return error("close(fd_out): %s", strerror(errno));
+    }
+    fd_out = -1;
+  }
+  return 0;
+}
+
+u1* OutputZipFile::NewFile(const char* filename, const u4 attr) {
+  header_ptr = WriteLocalFileHeader(filename, attr);
+  return q;
+}
+
+int OutputZipFile::FinishFile(size_t filelength, bool compress) {
+  size_t compressed_size =
+      WriteFileSizeInLocalFileHeader(header_ptr, filelength, compress);
+  entries_.back()->compressed_length = compressed_size;
+  entries_.back()->uncompressed_length = filelength;
+  if (compressed_size < filelength) {
+    entries_.back()->compression_method = COMPRESSION_METHOD_DEFLATED;
+  } else {
+    entries_.back()->compression_method = COMPRESSION_METHOD_STORED;
+  }
+  q += compressed_size;
+  return 0;
+}
+
+ZipBuilder* ZipBuilder::Create(const char* zip_file, u8 estimated_size) {
+  if (estimated_size > kMaximumOutputSize) {
+    fprintf(stderr,
+            "Uncompressed input jar has size %llu, "
+            "which exceeds the maximum supported output size %llu.\n"
+            "Assuming that ijar will be smaller and hoping for the best.\n",
+            estimated_size, kMaximumOutputSize);
+    estimated_size = kMaximumOutputSize;
+  }
+
+  int fd_out = open(zip_file, O_CREAT|O_RDWR|O_TRUNC, 0644);
+  if (fd_out < 0) {
+    return NULL;
+  }
+
+  // Create mmap-able sparse file
+  if (ftruncate(fd_out, estimated_size) < 0) {
+    return NULL;
+  }
+
+  // Ensure that any buffer overflow in JarStripper will result in
+  // SIGSEGV or SIGBUS by over-allocating beyond the end of the file.
+  size_t mmap_length = std::min(estimated_size + sysconf(_SC_PAGESIZE),
+                                (u8) std::numeric_limits<size_t>::max());
+
+  void *zipdata_out = mmap(NULL, mmap_length, PROT_WRITE,
+                           MAP_SHARED, fd_out, 0);
+  if (zipdata_out == MAP_FAILED) {
+    fprintf(stderr, "output_length=%llu\n", estimated_size);
+    return NULL;
+  }
+
+  return new OutputZipFile(fd_out, (u1*) zipdata_out);
+}
+
+u8 ZipBuilder::EstimateSize(char **files) {
+  struct stat statst;
+  // Digital signature field size = 6, End of central directory = 22, Total = 28
+  u8 size = 28;
+  // Count the size of all the files in the input to estimate the size of the
+  // output.
+  for (int i = 0; files[i] != NULL; i++) {
+    if (stat(files[i], &statst) != 0) {
+      fprintf(stderr, "File %s does not seem to exist.", files[i]);
+      return 0;
+    }
+    size += statst.st_size;
+    // Add sizes of Zip meta data
+    // local file header = 30 bytes
+    // data descriptor = 12 bytes
+    // central directory descriptor = 46 bytes
+    //    Total: 88bytes
+    size += 88;
+    // The filename is stored twice (once in the central directory
+    // and once in the local file header).
+    size += strlen(files[i]) * 2;
+  }
+  return size;
+}
+
+}  // namespace devtools_ijar