OLD | NEW |
(Empty) | |
| 1 /* |
| 2 * jdatadst.c |
| 3 * |
| 4 * Copyright (C) 1994-1996, Thomas G. Lane. |
| 5 * This file is part of the Independent JPEG Group's software. |
| 6 * For conditions of distribution and use, see the accompanying README file. |
| 7 * |
| 8 * This file contains compression data destination routines for the case of |
| 9 * emitting JPEG data to a file (or any stdio stream). While these routines |
| 10 * are sufficient for most applications, some will want to use a different |
| 11 * destination manager. |
| 12 * IMPORTANT: we assume that fwrite() will correctly transcribe an array of |
| 13 * JOCTETs into 8-bit-wide elements on external storage. If char is wider |
| 14 * than 8 bits on your machine, you may need to do some tweaking. |
| 15 */ |
| 16 |
| 17 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */ |
| 18 #include "jinclude.h" |
| 19 #include "jpeglib.h" |
| 20 #include "jerror.h" |
| 21 |
| 22 |
| 23 /* Expanded data destination object for stdio output */ |
| 24 |
| 25 typedef struct { |
| 26 struct jpeg_destination_mgr pub; /* public fields */ |
| 27 |
| 28 FILE * outfile; /* target stream */ |
| 29 JOCTET * buffer; /* start of buffer */ |
| 30 } my_destination_mgr; |
| 31 |
| 32 typedef my_destination_mgr * my_dest_ptr; |
| 33 |
| 34 #define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */ |
| 35 |
| 36 |
| 37 /* |
| 38 * Initialize destination --- called by jpeg_start_compress |
| 39 * before any data is actually written. |
| 40 */ |
| 41 |
| 42 METHODDEF(void) |
| 43 init_destination (j_compress_ptr cinfo) |
| 44 { |
| 45 my_dest_ptr dest = (my_dest_ptr) cinfo->dest; |
| 46 |
| 47 /* Allocate the output buffer --- it will be released when done with image */ |
| 48 dest->buffer = (JOCTET *) |
| 49 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 50 OUTPUT_BUF_SIZE * SIZEOF(JOCTET)); |
| 51 |
| 52 dest->pub.next_output_byte = dest->buffer; |
| 53 dest->pub.free_in_buffer = OUTPUT_BUF_SIZE; |
| 54 } |
| 55 |
| 56 |
| 57 /* |
| 58 * Empty the output buffer --- called whenever buffer fills up. |
| 59 * |
| 60 * In typical applications, this should write the entire output buffer |
| 61 * (ignoring the current state of next_output_byte & free_in_buffer), |
| 62 * reset the pointer & count to the start of the buffer, and return TRUE |
| 63 * indicating that the buffer has been dumped. |
| 64 * |
| 65 * In applications that need to be able to suspend compression due to output |
| 66 * overrun, a FALSE return indicates that the buffer cannot be emptied now. |
| 67 * In this situation, the compressor will return to its caller (possibly with |
| 68 * an indication that it has not accepted all the supplied scanlines). The |
| 69 * application should resume compression after it has made more room in the |
| 70 * output buffer. Note that there are substantial restrictions on the use of |
| 71 * suspension --- see the documentation. |
| 72 * |
| 73 * When suspending, the compressor will back up to a convenient restart point |
| 74 * (typically the start of the current MCU). next_output_byte & free_in_buffer |
| 75 * indicate where the restart point will be if the current call returns FALSE. |
| 76 * Data beyond this point will be regenerated after resumption, so do not |
| 77 * write it out when emptying the buffer externally. |
| 78 */ |
| 79 |
| 80 METHODDEF(boolean) |
| 81 empty_output_buffer (j_compress_ptr cinfo) |
| 82 { |
| 83 my_dest_ptr dest = (my_dest_ptr) cinfo->dest; |
| 84 |
| 85 if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) != |
| 86 (size_t) OUTPUT_BUF_SIZE) |
| 87 ERREXIT(cinfo, JERR_FILE_WRITE); |
| 88 |
| 89 dest->pub.next_output_byte = dest->buffer; |
| 90 dest->pub.free_in_buffer = OUTPUT_BUF_SIZE; |
| 91 |
| 92 return TRUE; |
| 93 } |
| 94 |
| 95 |
| 96 /* |
| 97 * Terminate destination --- called by jpeg_finish_compress |
| 98 * after all data has been written. Usually needs to flush buffer. |
| 99 * |
| 100 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding |
| 101 * application must deal with any cleanup that should happen even |
| 102 * for error exit. |
| 103 */ |
| 104 |
| 105 METHODDEF(void) |
| 106 term_destination (j_compress_ptr cinfo) |
| 107 { |
| 108 my_dest_ptr dest = (my_dest_ptr) cinfo->dest; |
| 109 size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer; |
| 110 |
| 111 /* Write any data remaining in the buffer */ |
| 112 if (datacount > 0) { |
| 113 if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount) |
| 114 ERREXIT(cinfo, JERR_FILE_WRITE); |
| 115 } |
| 116 fflush(dest->outfile); |
| 117 /* Make sure we wrote the output file OK */ |
| 118 if (ferror(dest->outfile)) |
| 119 ERREXIT(cinfo, JERR_FILE_WRITE); |
| 120 } |
| 121 |
| 122 |
| 123 /* |
| 124 * Prepare for output to a stdio stream. |
| 125 * The caller must have already opened the stream, and is responsible |
| 126 * for closing it after finishing compression. |
| 127 */ |
| 128 |
| 129 GLOBAL(void) |
| 130 jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile) |
| 131 { |
| 132 my_dest_ptr dest; |
| 133 |
| 134 /* The destination object is made permanent so that multiple JPEG images |
| 135 * can be written to the same file without re-executing jpeg_stdio_dest. |
| 136 * This makes it dangerous to use this manager and a different destination |
| 137 * manager serially with the same JPEG object, because their private object |
| 138 * sizes may be different. Caveat programmer. |
| 139 */ |
| 140 if (cinfo->dest == NULL) { /* first time for this JPEG object? */ |
| 141 cinfo->dest = (struct jpeg_destination_mgr *) |
| 142 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, |
| 143 SIZEOF(my_destination_mgr)); |
| 144 } |
| 145 |
| 146 dest = (my_dest_ptr) cinfo->dest; |
| 147 dest->pub.init_destination = init_destination; |
| 148 dest->pub.empty_output_buffer = empty_output_buffer; |
| 149 dest->pub.term_destination = term_destination; |
| 150 dest->outfile = outfile; |
| 151 } |
OLD | NEW |