ReactOS 0.4.15-dev-7201-g2de6e75
jdatasrc.c
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1/*
2 * jdatasrc.c
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * Modified 2009-2019 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains decompression data source routines for the case of
10 * reading JPEG data from memory or from a file (or any stdio stream).
11 * While these routines are sufficient for most applications,
12 * some will want to use a different source manager.
13 * IMPORTANT: we assume that fread() will correctly transcribe an array of
14 * JOCTETs from 8-bit-wide elements on external storage. If char is wider
15 * than 8 bits on your machine, you may need to do some tweaking.
16 */
17
18/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
19#include "jinclude.h"
20#include "jpeglib.h"
21#include "jerror.h"
22
23
24/* Expanded data source object for stdio input */
25
26typedef struct {
27 struct jpeg_source_mgr pub; /* public fields */
28
29 FILE * infile; /* source stream */
30 JOCTET * buffer; /* start of buffer */
31 boolean start_of_file; /* have we gotten any data yet? */
33
35
36#define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
37
38
39/*
40 * Initialize source --- called by jpeg_read_header
41 * before any data is actually read.
42 */
43
44METHODDEF(void)
46{
47 my_src_ptr src = (my_src_ptr) cinfo->src;
48
49 /* We reset the empty-input-file flag for each image,
50 * but we don't clear the input buffer.
51 * This is correct behavior for reading a series of images from one source.
52 */
54}
55
56METHODDEF(void)
58{
59 /* no work necessary here */
60}
61
62
63/*
64 * Fill the input buffer --- called whenever buffer is emptied.
65 *
66 * In typical applications, this should read fresh data into the buffer
67 * (ignoring the current state of next_input_byte & bytes_in_buffer),
68 * reset the pointer & count to the start of the buffer, and return TRUE
69 * indicating that the buffer has been reloaded. It is not necessary to
70 * fill the buffer entirely, only to obtain at least one more byte.
71 *
72 * There is no such thing as an EOF return. If the end of the file has been
73 * reached, the routine has a choice of ERREXIT() or inserting fake data into
74 * the buffer. In most cases, generating a warning message and inserting a
75 * fake EOI marker is the best course of action --- this will allow the
76 * decompressor to output however much of the image is there. However,
77 * the resulting error message is misleading if the real problem is an empty
78 * input file, so we handle that case specially.
79 *
80 * In applications that need to be able to suspend compression due to input
81 * not being available yet, a FALSE return indicates that no more data can be
82 * obtained right now, but more may be forthcoming later. In this situation,
83 * the decompressor will return to its caller (with an indication of the
84 * number of scanlines it has read, if any). The application should resume
85 * decompression after it has loaded more data into the input buffer. Note
86 * that there are substantial restrictions on the use of suspension --- see
87 * the documentation.
88 *
89 * When suspending, the decompressor will back up to a convenient restart point
90 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
91 * indicate where the restart point will be if the current call returns FALSE.
92 * Data beyond this point must be rescanned after resumption, so move it to
93 * the front of the buffer rather than discarding it.
94 */
95
96METHODDEF(boolean)
98{
99 my_src_ptr src = (my_src_ptr) cinfo->src;
100 size_t nbytes;
101
102 nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
103
104 if (nbytes <= 0) {
105 if (src->start_of_file) /* Treat empty input file as fatal error */
106 ERREXIT(cinfo, JERR_INPUT_EMPTY);
107 WARNMS(cinfo, JWRN_JPEG_EOF);
108 /* Insert a fake EOI marker */
109 src->buffer[0] = (JOCTET) 0xFF;
110 src->buffer[1] = (JOCTET) JPEG_EOI;
111 nbytes = 2;
112 }
113
114 src->pub.next_input_byte = src->buffer;
115 src->pub.bytes_in_buffer = nbytes;
116 src->start_of_file = FALSE;
117
118 return TRUE;
119}
120
121METHODDEF(boolean)
123{
124 static const JOCTET mybuffer[4] = {
125 (JOCTET) 0xFF, (JOCTET) JPEG_EOI, 0, 0
126 };
127
128 /* The whole JPEG data is expected to reside in the supplied memory
129 * buffer, so any request for more data beyond the given buffer size
130 * is treated as an error.
131 */
132 WARNMS(cinfo, JWRN_JPEG_EOF);
133
134 /* Insert a fake EOI marker */
135
136 cinfo->src->next_input_byte = mybuffer;
137 cinfo->src->bytes_in_buffer = 2;
138
139 return TRUE;
140}
141
142
143/*
144 * Skip data --- used to skip over a potentially large amount of
145 * uninteresting data (such as an APPn marker).
146 *
147 * Writers of suspendable-input applications must note that skip_input_data
148 * is not granted the right to give a suspension return. If the skip extends
149 * beyond the data currently in the buffer, the buffer can be marked empty so
150 * that the next read will cause a fill_input_buffer call that can suspend.
151 * Arranging for additional bytes to be discarded before reloading the input
152 * buffer is the application writer's problem.
153 */
154
155METHODDEF(void)
156skip_input_data (j_decompress_ptr cinfo, long num_bytes)
157{
158 struct jpeg_source_mgr * src = cinfo->src;
159 size_t nbytes;
160
161 /* Just a dumb implementation for now. Could use fseek() except
162 * it doesn't work on pipes. Not clear that being smart is worth
163 * any trouble anyway --- large skips are infrequent.
164 */
165 if (num_bytes > 0) {
166 nbytes = (size_t) num_bytes;
167 while (nbytes > src->bytes_in_buffer) {
168 nbytes -= src->bytes_in_buffer;
169 (void) (*src->fill_input_buffer) (cinfo);
170 /* note we assume that fill_input_buffer will never return FALSE,
171 * so suspension need not be handled.
172 */
173 }
174 src->next_input_byte += nbytes;
175 src->bytes_in_buffer -= nbytes;
176 }
177}
178
179
180/*
181 * An additional method that can be provided by data source modules is the
182 * resync_to_restart method for error recovery in the presence of RST markers.
183 * For the moment, this source module just uses the default resync method
184 * provided by the JPEG library. That method assumes that no backtracking
185 * is possible.
186 */
187
188
189/*
190 * Terminate source --- called by jpeg_finish_decompress
191 * after all data has been read. Often a no-op.
192 *
193 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
194 * application must deal with any cleanup that should happen even
195 * for error exit.
196 */
197
198METHODDEF(void)
200{
201 /* no work necessary here */
202}
203
204
205/*
206 * Prepare for input from a stdio stream.
207 * The caller must have already opened the stream, and is responsible
208 * for closing it after finishing decompression.
209 */
210
211GLOBAL(void)
213{
215
216 /* The source object and input buffer are made permanent so that a series
217 * of JPEG images can be read from the same file by calling jpeg_stdio_src
218 * only before the first one. (If we discarded the buffer at the end of
219 * one image, we'd likely lose the start of the next one.)
220 * This makes it unsafe to use this manager and a different source
221 * manager serially with the same JPEG object. Caveat programmer.
222 */
223 if (cinfo->src == NULL) { /* first time for this JPEG object? */
224 cinfo->src = (struct jpeg_source_mgr *) (*cinfo->mem->alloc_small)
226 src = (my_src_ptr) cinfo->src;
227 src->buffer = (JOCTET *) (*cinfo->mem->alloc_small)
229 }
230
231 src = (my_src_ptr) cinfo->src;
232 src->pub.init_source = init_source;
233 src->pub.fill_input_buffer = fill_input_buffer;
234 src->pub.skip_input_data = skip_input_data;
235 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
236 src->pub.term_source = term_source;
237 src->infile = infile;
238 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
239 src->pub.next_input_byte = NULL; /* until buffer loaded */
240}
241
242
243/*
244 * Prepare for input from a supplied memory buffer.
245 * The buffer must contain the whole JPEG data.
246 */
247
248GLOBAL(void)
250 const unsigned char * inbuffer, size_t insize)
251{
252 struct jpeg_source_mgr * src;
253
254 if (inbuffer == NULL || insize == 0) /* Treat empty input as fatal error */
255 ERREXIT(cinfo, JERR_INPUT_EMPTY);
256
257 /* The source object is made permanent so that a series of JPEG images
258 * can be read from the same buffer by calling jpeg_mem_src only before
259 * the first one.
260 */
261 if (cinfo->src == NULL) { /* first time for this JPEG object? */
262 cinfo->src = (struct jpeg_source_mgr *) (*cinfo->mem->alloc_small)
264 }
265
266 src = cinfo->src;
267 src->init_source = init_mem_source;
268 src->fill_input_buffer = fill_mem_input_buffer;
269 src->skip_input_data = skip_input_data;
270 src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
271 src->term_source = term_source;
272 src->bytes_in_buffer = insize;
273 src->next_input_byte = (const JOCTET *) inbuffer;
274}
#define SIZEOF(_ar)
Definition: calc.h:97
#define NULL
Definition: types.h:112
#define TRUE
Definition: types.h:120
#define FALSE
Definition: types.h:117
__kernel_size_t size_t
Definition: linux.h:237
GLenum src
Definition: glext.h:6340
term_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:199
jpeg_mem_src(j_decompress_ptr cinfo, const unsigned char *inbuffer, size_t insize)
Definition: jdatasrc.c:249
my_source_mgr * my_src_ptr
Definition: jdatasrc.c:34
jpeg_stdio_src(j_decompress_ptr cinfo, FILE *infile)
Definition: jdatasrc.c:212
#define INPUT_BUF_SIZE
Definition: jdatasrc.c:36
fill_input_buffer(j_decompress_ptr cinfo)
Definition: jdatasrc.c:97
init_mem_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:57
fill_mem_input_buffer(j_decompress_ptr cinfo)
Definition: jdatasrc.c:122
init_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:45
skip_input_data(j_decompress_ptr cinfo, long num_bytes)
Definition: jdatasrc.c:156
jpeg_resync_to_restart(j_decompress_ptr cinfo, int desired)
Definition: jdmarker.c:1338
#define WARNMS(cinfo, code)
Definition: jerror.h:251
#define JFREAD(file, buf, sizeofbuf)
Definition: jinclude.h:92
char JOCTET
Definition: jmorecfg.h:167
#define METHODDEF(type)
Definition: jmorecfg.h:287
#define GLOBAL(type)
Definition: jmorecfg.h:291
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:284
#define JPEG_EOI
Definition: jpeglib.h:1127
const unsigned char * inbuffer
Definition: jpeglib.h:983
const unsigned char size_t insize
Definition: jpeglib.h:984
#define JPOOL_PERMANENT
Definition: jpeglib.h:807
#define ERREXIT(msg)
Definition: rdjpgcom.c:72
static FILE * infile
Definition: rdjpgcom.c:65
size_t bytes_in_buffer
Definition: jpeglib.h:786
FILE * infile
Definition: jdatasrc.c:29
boolean start_of_file
Definition: jdatasrc.c:31
JOCTET * buffer
Definition: jdatasrc.c:30
#define const
Definition: zconf.h:233