source: trunk/libjpeg/jdatadst.c @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 15 years ago

needed libs update

File size: 5.1 KB
Line 
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
25typedef 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
32typedef 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
42METHODDEF(void)
43init_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
80METHODDEF(boolean)
81empty_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
105METHODDEF(void)
106term_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
129GLOBAL(void)
130jpeg_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}
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