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, 2022, D. R. Commander.
9 * For conditions of distribution and use, see the accompanying README.ijg
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.
21 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
27 /* Expanded data source object for stdio input */
30 struct jpeg_source_mgr pub
; /* public fields */
32 FILE *infile
; /* source stream */
33 JOCTET
*buffer
; /* start of buffer */
34 boolean start_of_file
; /* have we gotten any data yet? */
37 typedef my_source_mgr
*my_src_ptr
;
39 #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
43 * Initialize source --- called by jpeg_read_header
44 * before any data is actually read.
48 init_source(j_decompress_ptr cinfo
)
50 my_src_ptr src
= (my_src_ptr
)cinfo
->src
;
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.
56 src
->start_of_file
= TRUE
;
59 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
61 init_mem_source(j_decompress_ptr cinfo
)
63 /* no work necessary here */
69 * Fill the input buffer --- called whenever buffer is emptied.
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.
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.
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
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.
102 fill_input_buffer(j_decompress_ptr cinfo
)
104 my_src_ptr src
= (my_src_ptr
)cinfo
->src
;
107 nbytes
= fread(src
->buffer
, 1, INPUT_BUF_SIZE
, src
->infile
);
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
;
119 src
->pub
.next_input_byte
= src
->buffer
;
120 src
->pub
.bytes_in_buffer
= nbytes
;
121 src
->start_of_file
= FALSE
;
126 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
128 fill_mem_input_buffer(j_decompress_ptr cinfo
)
130 static const JOCTET mybuffer
[4] = {
131 (JOCTET
)0xFF, (JOCTET
)JPEG_EOI
, 0, 0
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.
138 WARNMS(cinfo
, JWRN_JPEG_EOF
);
140 /* Insert a fake EOI marker */
142 cinfo
->src
->next_input_byte
= mybuffer
;
143 cinfo
->src
->bytes_in_buffer
= 2;
151 * Skip data --- used to skip over a potentially large amount of
152 * uninteresting data (such as an APPn marker).
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.
163 skip_input_data(j_decompress_ptr cinfo
, long num_bytes
)
165 struct jpeg_source_mgr
*src
= cinfo
->src
;
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.
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.
179 src
->next_input_byte
+= (size_t)num_bytes
;
180 src
->bytes_in_buffer
-= (size_t)num_bytes
;
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
195 * Terminate source --- called by jpeg_finish_decompress
196 * after all data has been read. Often a no-op.
198 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
199 * application must deal with any cleanup that should happen even
204 term_source(j_decompress_ptr cinfo
)
206 /* no work necessary here */
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.
217 jpeg_stdio_src(j_decompress_ptr cinfo
, FILE *infile
)
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.)
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.
241 ERREXIT(cinfo
, JERR_BUFFER_SIZE
);
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 */
256 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
258 * Prepare for input from a supplied memory buffer.
259 * The buffer must contain the whole JPEG data.
263 jpeg_mem_src(j_decompress_ptr cinfo
, const unsigned char *inbuffer
,
264 unsigned long insize
)
266 struct jpeg_source_mgr
*src
;
268 if (inbuffer
== NULL
|| insize
== 0) /* Treat empty input as fatal error */
269 ERREXIT(cinfo
, JERR_INPUT_EMPTY
);
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
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
283 ERREXIT(cinfo
, JERR_BUFFER_SIZE
);
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
;