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
29typedef 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
37typedef 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
47METHODDEF(void)
48init_source (j_decompress_ptr cinfo)
49{
50 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 src->start_of_file = TRUE;
57}
58
59#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
60METHODDEF(void)
61init_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
101METHODDEF(boolean)
102fill_input_buffer (j_decompress_ptr cinfo)
103{
104 my_src_ptr src = (my_src_ptr) cinfo->src;
105 size_t nbytes;
106
107 nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
108
109 if (nbytes <= 0) {
110 if (src->start_of_file) /* Treat empty input file as fatal error */
111 ERREXIT(cinfo, JERR_INPUT_EMPTY);
112 WARNMS(cinfo, JWRN_JPEG_EOF);
113 /* Insert a fake EOI marker */
114 src->buffer[0] = (JOCTET) 0xFF;
115 src->buffer[1] = (JOCTET) JPEG_EOI;
116 nbytes = 2;
117 }
118
119 src->pub.next_input_byte = src->buffer;
120 src->pub.bytes_in_buffer = nbytes;
121 src->start_of_file = FALSE;
122
123 return TRUE;
124}
125
126#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
127METHODDEF(boolean)
128fill_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
162METHODDEF(void)
163skip_input_data (j_decompress_ptr cinfo, long num_bytes)
164{
165 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 if (num_bytes > 0) {
172 while (num_bytes > (long) src->bytes_in_buffer) {
173 num_bytes -= (long) src->bytes_in_buffer;
174 (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 src->next_input_byte += (size_t) num_bytes;
180 src->bytes_in_buffer -= (size_t) num_bytes;
181 }
182}
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
203METHODDEF(void)
204term_source (j_decompress_ptr cinfo)
205{
206 /* no work necessary here */
207}
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
216GLOBAL(void)
217jpeg_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 if (cinfo->src == NULL) { /* first time for this JPEG object? */
227 cinfo->src = (struct jpeg_source_mgr *)
228 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
229 sizeof(my_source_mgr));
230 src = (my_src_ptr) cinfo->src;
231 src->buffer = (JOCTET *)
232 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
233 INPUT_BUF_SIZE * sizeof(JOCTET));
234 } 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 ERREXIT(cinfo, JERR_BUFFER_SIZE);
242 }
243
244 src = (my_src_ptr) cinfo->src;
245 src->pub.init_source = init_source;
246 src->pub.fill_input_buffer = fill_input_buffer;
247 src->pub.skip_input_data = skip_input_data;
248 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
249 src->pub.term_source = term_source;
250 src->infile = infile;
251 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
252 src->pub.next_input_byte = NULL; /* until buffer loaded */
253}
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
262GLOBAL(void)
263jpeg_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
296