ReactOS  0.4.14-dev-854-gb9426a3
jdatasrc.c
Go to the documentation of this file.
1 /*
2  * jdatasrc.c
3  *
4  * Copyright (C) 1994-1996, Thomas G. Lane.
5  * Modified 2009-2015 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 typedef 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 
44 METHODDEF(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 
56 METHODDEF(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 
96 METHODDEF(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 
121 METHODDEF(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 
155 METHODDEF(void)
157 {
158  struct jpeg_source_mgr * src = cinfo->src;
159 
160  /* Just a dumb implementation for now. Could use fseek() except
161  * it doesn't work on pipes. Not clear that being smart is worth
162  * any trouble anyway --- large skips are infrequent.
163  */
164  if (num_bytes > 0) {
165  while (num_bytes > (long) src->bytes_in_buffer) {
166  num_bytes -= (long) src->bytes_in_buffer;
167  (void) (*src->fill_input_buffer) (cinfo);
168  /* note we assume that fill_input_buffer will never return FALSE,
169  * so suspension need not be handled.
170  */
171  }
172  src->next_input_byte += (size_t) num_bytes;
173  src->bytes_in_buffer -= (size_t) num_bytes;
174  }
175 }
176 
177 
178 /*
179  * An additional method that can be provided by data source modules is the
180  * resync_to_restart method for error recovery in the presence of RST markers.
181  * For the moment, this source module just uses the default resync method
182  * provided by the JPEG library. That method assumes that no backtracking
183  * is possible.
184  */
185 
186 
187 /*
188  * Terminate source --- called by jpeg_finish_decompress
189  * after all data has been read. Often a no-op.
190  *
191  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
192  * application must deal with any cleanup that should happen even
193  * for error exit.
194  */
195 
196 METHODDEF(void)
198 {
199  /* no work necessary here */
200 }
201 
202 
203 /*
204  * Prepare for input from a stdio stream.
205  * The caller must have already opened the stream, and is responsible
206  * for closing it after finishing decompression.
207  */
208 
209 GLOBAL(void)
211 {
212  my_src_ptr src;
213 
214  /* The source object and input buffer are made permanent so that a series
215  * of JPEG images can be read from the same file by calling jpeg_stdio_src
216  * only before the first one. (If we discarded the buffer at the end of
217  * one image, we'd likely lose the start of the next one.)
218  * This makes it unsafe to use this manager and a different source
219  * manager serially with the same JPEG object. Caveat programmer.
220  */
221  if (cinfo->src == NULL) { /* first time for this JPEG object? */
222  cinfo->src = (struct jpeg_source_mgr *)
223  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
225  src = (my_src_ptr) cinfo->src;
226  src->buffer = (JOCTET *)
227  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
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 
248 GLOBAL(void)
250  const unsigned char * inbuffer, unsigned long 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 *)
263  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
264  SIZEOF(struct jpeg_source_mgr));
265  }
266 
267  src = cinfo->src;
268  src->init_source = init_mem_source;
269  src->fill_input_buffer = fill_mem_input_buffer;
270  src->skip_input_data = skip_input_data;
271  src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
272  src->term_source = term_source;
273  src->bytes_in_buffer = (size_t) insize;
274  src->next_input_byte = (const JOCTET *) inbuffer;
275 }
const unsigned char * inbuffer
Definition: jpeglib.h:982
#define TRUE
Definition: types.h:120
#define ERREXIT(msg)
Definition: rdjpgcom.c:72
term_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:197
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:284
static FILE * infile
Definition: rdjpgcom.c:65
JOCTET * buffer
Definition: jdatasrc.c:30
fill_mem_input_buffer(j_decompress_ptr cinfo)
Definition: jdatasrc.c:122
#define JFREAD(file, buf, sizeofbuf)
Definition: jinclude.h:92
jpeg_mem_src(j_decompress_ptr cinfo, const unsigned char *inbuffer, unsigned long insize)
Definition: jdatasrc.c:249
#define SIZEOF(_ar)
Definition: calc.h:97
init_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:45
smooth NULL
Definition: ftsmooth.c:416
#define INPUT_BUF_SIZE
Definition: jdatasrc.c:36
FILE * infile
Definition: jdatasrc.c:29
__kernel_size_t size_t
Definition: linux.h:237
init_mem_source(j_decompress_ptr cinfo)
Definition: jdatasrc.c:57
jpeg_stdio_src(j_decompress_ptr cinfo, FILE *infile)
Definition: jdatasrc.c:210
ed2 num_bytes
Definition: write.c:2846
#define WARNMS(cinfo, code)
Definition: jerror.h:251
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:1343
const unsigned char unsigned long insize
Definition: jpeglib.h:982
GLenum src
Definition: glext.h:6340
#define GLOBAL(type)
Definition: jmorecfg.h:291
#define METHODDEF(type)
Definition: jmorecfg.h:287
#define JPEG_EOI
Definition: jpeglib.h:1124
boolean start_of_file
Definition: jdatasrc.c:31
#define long
Definition: qsort.c:33
my_source_mgr * my_src_ptr
Definition: jdatasrc.c:34
#define JPOOL_PERMANENT
Definition: jpeglib.h:807
#define const
Definition: zconf.h:230
char JOCTET
Definition: jmorecfg.h:167
fill_input_buffer(j_decompress_ptr cinfo)
Definition: jdatasrc.c:97