Subversion Repositories Kolibri OS

Rev

Blame | Last modification | View Log | RSS feed

  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. }
  152.