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comparison mupdf-source/thirdparty/libjpeg/jdatasrc.c @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * jdatasrc.c
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * Modified 2009-2022 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
26 #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
27
28 typedef struct {
29 struct jpeg_source_mgr pub; /* public fields */
30
31 FILE * infile; /* source stream */
32 JOCTET buffer[INPUT_BUF_SIZE]; /* input buffer */
33 boolean start_of_file; /* have we gotten any data yet? */
34 } my_source_mgr;
35
36 typedef my_source_mgr * my_src_ptr;
37
38
39 /*
40 * Initialize source --- called by jpeg_read_header
41 * before any data is actually read.
42 */
43
44 METHODDEF(void)
45 init_source (j_decompress_ptr cinfo)
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 */
53 src->start_of_file = TRUE;
54 }
55
56 METHODDEF(void)
57 init_mem_source (j_decompress_ptr cinfo)
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
96 METHODDEF(boolean)
97 fill_input_buffer (j_decompress_ptr cinfo)
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
121 METHODDEF(boolean)
122 fill_mem_input_buffer (j_decompress_ptr cinfo)
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
155 METHODDEF(void)
156 skip_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
198 METHODDEF(void)
199 term_source (j_decompress_ptr cinfo)
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,
208 * and is responsible for closing it after finishing decompression.
209 */
210
211 GLOBAL(void)
212 jpeg_stdio_src (j_decompress_ptr cinfo, FILE * infile)
213 {
214 my_src_ptr src;
215
216 /* The source object including the input buffer is made permanent so that
217 * a series of JPEG images can be read from the same file by calling
218 * jpeg_stdio_src only before the first one. (If we discarded the buffer
219 * at the end of 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)
225 ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(my_source_mgr));
226 }
227
228 src = (my_src_ptr) cinfo->src;
229 src->pub.init_source = init_source;
230 src->pub.fill_input_buffer = fill_input_buffer;
231 src->pub.skip_input_data = skip_input_data;
232 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
233 src->pub.term_source = term_source;
234 src->infile = infile;
235 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
236 src->pub.next_input_byte = NULL; /* until buffer loaded */
237 }
238
239
240 /*
241 * Prepare for input from a supplied memory buffer.
242 * The buffer must contain the whole JPEG data.
243 */
244
245 GLOBAL(void)
246 jpeg_mem_src (j_decompress_ptr cinfo,
247 const unsigned char * inbuffer, size_t insize)
248 {
249 struct jpeg_source_mgr * src;
250
251 if (inbuffer == NULL || insize == 0) /* Treat empty input as fatal error */
252 ERREXIT(cinfo, JERR_INPUT_EMPTY);
253
254 /* The source object is made permanent so that a series of JPEG images
255 * can be read from the same buffer by calling jpeg_mem_src only before
256 * the first one.
257 */
258 if (cinfo->src == NULL) { /* first time for this JPEG object? */
259 cinfo->src = (struct jpeg_source_mgr *) (*cinfo->mem->alloc_small)
260 ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(struct jpeg_source_mgr));
261 }
262
263 src = cinfo->src;
264 src->init_source = init_mem_source;
265 src->fill_input_buffer = fill_mem_input_buffer;
266 src->skip_input_data = skip_input_data;
267 src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
268 src->term_source = term_source;
269 src->bytes_in_buffer = insize;
270 src->next_input_byte = (const JOCTET *) inbuffer;
271 }