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