Line data Source code
1 : /*
2 : * jdatasrc.c
3 : *
4 : * This file was part of the Independent JPEG Group's software:
5 : * Copyright (C) 1994-1996, Thomas G. Lane.
6 : * Modified 2009-2011 by Guido Vollbeding.
7 : * libjpeg-turbo Modifications:
8 : * Copyright (C) 2013, 2016, D. R. Commander.
9 : * For conditions of distribution and use, see the accompanying README.ijg
10 : * file.
11 : *
12 : * This file contains decompression data source routines for the case of
13 : * reading JPEG data from memory or from a file (or any stdio stream).
14 : * While these routines are sufficient for most applications,
15 : * some will want to use a different source manager.
16 : * IMPORTANT: we assume that fread() will correctly transcribe an array of
17 : * JOCTETs from 8-bit-wide elements on external storage. If char is wider
18 : * than 8 bits on your machine, you may need to do some tweaking.
19 : */
20 :
21 : /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
22 : #include "jinclude.h"
23 : #include "jpeglib.h"
24 : #include "jerror.h"
25 :
26 :
27 : /* Expanded data source object for stdio input */
28 :
29 : typedef struct {
30 : struct jpeg_source_mgr pub; /* public fields */
31 :
32 : FILE *infile; /* source stream */
33 : JOCTET *buffer; /* start of buffer */
34 : boolean start_of_file; /* have we gotten any data yet? */
35 : } my_source_mgr;
36 :
37 : typedef my_source_mgr *my_src_ptr;
38 :
39 : #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
40 :
41 :
42 : /*
43 : * Initialize source --- called by jpeg_read_header
44 : * before any data is actually read.
45 : */
46 :
47 : METHODDEF(void)
48 0 : init_source (j_decompress_ptr cinfo)
49 : {
50 0 : my_src_ptr src = (my_src_ptr) cinfo->src;
51 :
52 : /* We reset the empty-input-file flag for each image,
53 : * but we don't clear the input buffer.
54 : * This is correct behavior for reading a series of images from one source.
55 : */
56 0 : src->start_of_file = TRUE;
57 0 : }
58 :
59 : #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
60 : METHODDEF(void)
61 : init_mem_source (j_decompress_ptr cinfo)
62 : {
63 : /* no work necessary here */
64 : }
65 : #endif
66 :
67 :
68 : /*
69 : * Fill the input buffer --- called whenever buffer is emptied.
70 : *
71 : * In typical applications, this should read fresh data into the buffer
72 : * (ignoring the current state of next_input_byte & bytes_in_buffer),
73 : * reset the pointer & count to the start of the buffer, and return TRUE
74 : * indicating that the buffer has been reloaded. It is not necessary to
75 : * fill the buffer entirely, only to obtain at least one more byte.
76 : *
77 : * There is no such thing as an EOF return. If the end of the file has been
78 : * reached, the routine has a choice of ERREXIT() or inserting fake data into
79 : * the buffer. In most cases, generating a warning message and inserting a
80 : * fake EOI marker is the best course of action --- this will allow the
81 : * decompressor to output however much of the image is there. However,
82 : * the resulting error message is misleading if the real problem is an empty
83 : * input file, so we handle that case specially.
84 : *
85 : * In applications that need to be able to suspend compression due to input
86 : * not being available yet, a FALSE return indicates that no more data can be
87 : * obtained right now, but more may be forthcoming later. In this situation,
88 : * the decompressor will return to its caller (with an indication of the
89 : * number of scanlines it has read, if any). The application should resume
90 : * decompression after it has loaded more data into the input buffer. Note
91 : * that there are substantial restrictions on the use of suspension --- see
92 : * the documentation.
93 : *
94 : * When suspending, the decompressor will back up to a convenient restart point
95 : * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
96 : * indicate where the restart point will be if the current call returns FALSE.
97 : * Data beyond this point must be rescanned after resumption, so move it to
98 : * the front of the buffer rather than discarding it.
99 : */
100 :
101 : METHODDEF(boolean)
102 0 : fill_input_buffer (j_decompress_ptr cinfo)
103 : {
104 0 : my_src_ptr src = (my_src_ptr) cinfo->src;
105 : size_t nbytes;
106 :
107 0 : nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
108 :
109 0 : if (nbytes <= 0) {
110 0 : if (src->start_of_file) /* Treat empty input file as fatal error */
111 0 : ERREXIT(cinfo, JERR_INPUT_EMPTY);
112 0 : WARNMS(cinfo, JWRN_JPEG_EOF);
113 : /* Insert a fake EOI marker */
114 0 : src->buffer[0] = (JOCTET) 0xFF;
115 0 : src->buffer[1] = (JOCTET) JPEG_EOI;
116 0 : nbytes = 2;
117 : }
118 :
119 0 : src->pub.next_input_byte = src->buffer;
120 0 : src->pub.bytes_in_buffer = nbytes;
121 0 : src->start_of_file = FALSE;
122 :
123 0 : return TRUE;
124 : }
125 :
126 : #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
127 : METHODDEF(boolean)
128 : fill_mem_input_buffer (j_decompress_ptr cinfo)
129 : {
130 : static const JOCTET mybuffer[4] = {
131 : (JOCTET) 0xFF, (JOCTET) JPEG_EOI, 0, 0
132 : };
133 :
134 : /* The whole JPEG data is expected to reside in the supplied memory
135 : * buffer, so any request for more data beyond the given buffer size
136 : * is treated as an error.
137 : */
138 : WARNMS(cinfo, JWRN_JPEG_EOF);
139 :
140 : /* Insert a fake EOI marker */
141 :
142 : cinfo->src->next_input_byte = mybuffer;
143 : cinfo->src->bytes_in_buffer = 2;
144 :
145 : return TRUE;
146 : }
147 : #endif
148 :
149 :
150 : /*
151 : * Skip data --- used to skip over a potentially large amount of
152 : * uninteresting data (such as an APPn marker).
153 : *
154 : * Writers of suspendable-input applications must note that skip_input_data
155 : * is not granted the right to give a suspension return. If the skip extends
156 : * beyond the data currently in the buffer, the buffer can be marked empty so
157 : * that the next read will cause a fill_input_buffer call that can suspend.
158 : * Arranging for additional bytes to be discarded before reloading the input
159 : * buffer is the application writer's problem.
160 : */
161 :
162 : METHODDEF(void)
163 0 : skip_input_data (j_decompress_ptr cinfo, long num_bytes)
164 : {
165 0 : struct jpeg_source_mgr *src = cinfo->src;
166 :
167 : /* Just a dumb implementation for now. Could use fseek() except
168 : * it doesn't work on pipes. Not clear that being smart is worth
169 : * any trouble anyway --- large skips are infrequent.
170 : */
171 0 : if (num_bytes > 0) {
172 0 : while (num_bytes > (long) src->bytes_in_buffer) {
173 0 : num_bytes -= (long) src->bytes_in_buffer;
174 0 : (void) (*src->fill_input_buffer) (cinfo);
175 : /* note we assume that fill_input_buffer will never return FALSE,
176 : * so suspension need not be handled.
177 : */
178 : }
179 0 : src->next_input_byte += (size_t) num_bytes;
180 0 : src->bytes_in_buffer -= (size_t) num_bytes;
181 : }
182 0 : }
183 :
184 :
185 : /*
186 : * An additional method that can be provided by data source modules is the
187 : * resync_to_restart method for error recovery in the presence of RST markers.
188 : * For the moment, this source module just uses the default resync method
189 : * provided by the JPEG library. That method assumes that no backtracking
190 : * is possible.
191 : */
192 :
193 :
194 : /*
195 : * Terminate source --- called by jpeg_finish_decompress
196 : * after all data has been read. Often a no-op.
197 : *
198 : * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
199 : * application must deal with any cleanup that should happen even
200 : * for error exit.
201 : */
202 :
203 : METHODDEF(void)
204 0 : term_source (j_decompress_ptr cinfo)
205 : {
206 : /* no work necessary here */
207 0 : }
208 :
209 :
210 : /*
211 : * Prepare for input from a stdio stream.
212 : * The caller must have already opened the stream, and is responsible
213 : * for closing it after finishing decompression.
214 : */
215 :
216 : GLOBAL(void)
217 0 : jpeg_stdio_src (j_decompress_ptr cinfo, FILE *infile)
218 : {
219 : my_src_ptr src;
220 :
221 : /* The source object and input buffer are made permanent so that a series
222 : * of JPEG images can be read from the same file by calling jpeg_stdio_src
223 : * only before the first one. (If we discarded the buffer at the end of
224 : * one image, we'd likely lose the start of the next one.)
225 : */
226 0 : if (cinfo->src == NULL) { /* first time for this JPEG object? */
227 0 : cinfo->src = (struct jpeg_source_mgr *)
228 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
229 : sizeof(my_source_mgr));
230 0 : src = (my_src_ptr) cinfo->src;
231 0 : src->buffer = (JOCTET *)
232 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
233 : INPUT_BUF_SIZE * sizeof(JOCTET));
234 0 : } else if (cinfo->src->init_source != init_source) {
235 : /* It is unsafe to reuse the existing source manager unless it was created
236 : * by this function. Otherwise, there is no guarantee that the opaque
237 : * structure is the right size. Note that we could just create a new
238 : * structure, but the old structure would not be freed until
239 : * jpeg_destroy_decompress() was called.
240 : */
241 0 : ERREXIT(cinfo, JERR_BUFFER_SIZE);
242 : }
243 :
244 0 : src = (my_src_ptr) cinfo->src;
245 0 : src->pub.init_source = init_source;
246 0 : src->pub.fill_input_buffer = fill_input_buffer;
247 0 : src->pub.skip_input_data = skip_input_data;
248 0 : src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
249 0 : src->pub.term_source = term_source;
250 0 : src->infile = infile;
251 0 : src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
252 0 : src->pub.next_input_byte = NULL; /* until buffer loaded */
253 0 : }
254 :
255 :
256 : #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
257 : /*
258 : * Prepare for input from a supplied memory buffer.
259 : * The buffer must contain the whole JPEG data.
260 : */
261 :
262 : GLOBAL(void)
263 : jpeg_mem_src (j_decompress_ptr cinfo,
264 : const unsigned char *inbuffer, unsigned long insize)
265 : {
266 : struct jpeg_source_mgr *src;
267 :
268 : if (inbuffer == NULL || insize == 0) /* Treat empty input as fatal error */
269 : ERREXIT(cinfo, JERR_INPUT_EMPTY);
270 :
271 : /* The source object is made permanent so that a series of JPEG images
272 : * can be read from the same buffer by calling jpeg_mem_src only before
273 : * the first one.
274 : */
275 : if (cinfo->src == NULL) { /* first time for this JPEG object? */
276 : cinfo->src = (struct jpeg_source_mgr *)
277 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
278 : sizeof(struct jpeg_source_mgr));
279 : } else if (cinfo->src->init_source != init_mem_source) {
280 : /* It is unsafe to reuse the existing source manager unless it was created
281 : * by this function.
282 : */
283 : ERREXIT(cinfo, JERR_BUFFER_SIZE);
284 : }
285 :
286 : src = cinfo->src;
287 : src->init_source = init_mem_source;
288 : src->fill_input_buffer = fill_mem_input_buffer;
289 : src->skip_input_data = skip_input_data;
290 : src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
291 : src->term_source = term_source;
292 : src->bytes_in_buffer = (size_t) insize;
293 : src->next_input_byte = (const JOCTET *) inbuffer;
294 : }
295 : #endif
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