4 * Copyright (C) 1994, Thomas G. Lane.
\r
5 * This file is part of the Independent JPEG Group's software.
\r
6 * For conditions of distribution and use, see the accompanying README file.
\r
8 * This file contains decompression data source routines for the case of
\r
9 * reading JPEG data from a file (or any stdio stream). While these routines
\r
10 * are sufficient for most applications, some will want to use a different
\r
12 * IMPORTANT: we assume that fread() will correctly transcribe an array of
\r
13 * JOCTETs from 8-bit-wide elements on external storage. If char is wider
\r
14 * than 8 bits on your machine, you may need to do some tweaking.
\r
18 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
\r
19 #include "jinclude.h"
\r
20 #include "radiant_jpeglib.h"
\r
23 //extern int leo_buf_size; // FIXME ? merged in from Alpha - replaced by my_source_mgr->src_size
\r
25 /* Expanded data source object for stdio input */
\r
28 struct jpeg_source_mgr pub; /* public fields */
\r
29 int src_size; // FIXME ? merged from Alpha
\r
30 unsigned char *infile; /* source stream */
\r
31 JOCTET * buffer; /* start of buffer */
\r
32 boolean start_of_file; /* have we gotten any data yet? */
\r
35 typedef my_source_mgr * my_src_ptr;
\r
37 #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
\r
41 * Initialize source --- called by jpeg_read_header
\r
42 * before any data is actually read.
\r
46 init_source (j_decompress_ptr cinfo)
\r
48 my_src_ptr src = (my_src_ptr) cinfo->src;
\r
50 /* We reset the empty-input-file flag for each image,
\r
51 * but we don't clear the input buffer.
\r
52 * This is correct behavior for reading a series of images from one source.
\r
54 src->start_of_file = TRUE;
\r
59 * Fill the input buffer --- called whenever buffer is emptied.
\r
61 * In typical applications, this should read fresh data into the buffer
\r
62 * (ignoring the current state of next_input_byte & bytes_in_buffer),
\r
63 * reset the pointer & count to the start of the buffer, and return TRUE
\r
64 * indicating that the buffer has been reloaded. It is not necessary to
\r
65 * fill the buffer entirely, only to obtain at least one more byte.
\r
67 * There is no such thing as an EOF return. If the end of the file has been
\r
68 * reached, the routine has a choice of ERREXIT() or inserting fake data into
\r
69 * the buffer. In most cases, generating a warning message and inserting a
\r
70 * fake EOI marker is the best course of action --- this will allow the
\r
71 * decompressor to output however much of the image is there. However,
\r
72 * the resulting error message is misleading if the real problem is an empty
\r
73 * input file, so we handle that case specially.
\r
75 * In applications that need to be able to suspend compression due to input
\r
76 * not being available yet, a FALSE return indicates that no more data can be
\r
77 * obtained right now, but more may be forthcoming later. In this situation,
\r
78 * the decompressor will return to its caller (with an indication of the
\r
79 * number of scanlines it has read, if any). The application should resume
\r
80 * decompression after it has loaded more data into the input buffer. Note
\r
81 * that there are substantial restrictions on the use of suspension --- see
\r
82 * the documentation.
\r
84 * When suspending, the decompressor will back up to a convenient restart point
\r
85 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
\r
86 * indicate where the restart point will be if the current call returns FALSE.
\r
87 * Data beyond this point must be rescanned after resumption, so move it to
\r
88 * the front of the buffer rather than discarding it.
\r
92 // FIXME ? merged in from Alpha
\r
93 fill_input_buffer (j_decompress_ptr cinfo)
\r
95 my_src_ptr src = (my_src_ptr) cinfo->src;
\r
98 if (src->src_size > INPUT_BUF_SIZE)
\r
99 nbytes = INPUT_BUF_SIZE;
\r
101 nbytes = src->src_size;
\r
103 memcpy (src->buffer, src->infile, nbytes);
\r
105 src->infile += nbytes;
\r
106 src->src_size -= nbytes;
\r
108 src->pub.next_input_byte = src->buffer;
\r
109 src->pub.bytes_in_buffer = nbytes;
\r
110 src->start_of_file = FALSE;
\r
117 * Skip data --- used to skip over a potentially large amount of
\r
118 * uninteresting data (such as an APPn marker).
\r
120 * Writers of suspendable-input applications must note that skip_input_data
\r
121 * is not granted the right to give a suspension return. If the skip extends
\r
122 * beyond the data currently in the buffer, the buffer can be marked empty so
\r
123 * that the next read will cause a fill_input_buffer call that can suspend.
\r
124 * Arranging for additional bytes to be discarded before reloading the input
\r
125 * buffer is the application writer's problem.
\r
129 skip_input_data (j_decompress_ptr cinfo, long num_bytes)
\r
131 my_src_ptr src = (my_src_ptr) cinfo->src;
\r
133 /* Just a dumb implementation for now. Could use fseek() except
\r
134 * it doesn't work on pipes. Not clear that being smart is worth
\r
135 * any trouble anyway --- large skips are infrequent.
\r
137 if (num_bytes > 0) {
\r
138 while (num_bytes > (long) src->pub.bytes_in_buffer) {
\r
139 num_bytes -= (long) src->pub.bytes_in_buffer;
\r
140 (void) fill_input_buffer(cinfo);
\r
141 /* note we assume that fill_input_buffer will never return FALSE,
\r
142 * so suspension need not be handled.
\r
145 src->pub.next_input_byte += (size_t) num_bytes;
\r
146 src->pub.bytes_in_buffer -= (size_t) num_bytes;
\r
152 * An additional method that can be provided by data source modules is the
\r
153 * resync_to_restart method for error recovery in the presence of RST markers.
\r
154 * For the moment, this source module just uses the default resync method
\r
155 * provided by the JPEG library. That method assumes that no backtracking
\r
161 * Terminate source --- called by jpeg_finish_decompress
\r
162 * after all data has been read. Often a no-op.
\r
164 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
\r
165 * application must deal with any cleanup that should happen even
\r
170 term_source (j_decompress_ptr cinfo)
\r
172 /* no work necessary here */
\r
177 * Prepare for input from a stdio stream.
\r
178 * The caller must have already opened the stream, and is responsible
\r
179 * for closing it after finishing decompression.
\r
183 jpeg_stdio_src (j_decompress_ptr cinfo, unsigned char *infile, int bufsize)
\r
187 /* The source object and input buffer are made permanent so that a series
\r
188 * of JPEG images can be read from the same file by calling jpeg_stdio_src
\r
189 * only before the first one. (If we discarded the buffer at the end of
\r
190 * one image, we'd likely lose the start of the next one.)
\r
191 * This makes it unsafe to use this manager and a different source
\r
192 * manager serially with the same JPEG object. Caveat programmer.
\r
194 if (cinfo->src == NULL) { /* first time for this JPEG object? */
\r
195 cinfo->src = (struct jpeg_source_mgr *)
\r
196 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
\r
197 SIZEOF(my_source_mgr));
\r
198 src = (my_src_ptr) cinfo->src;
\r
199 src->buffer = (JOCTET *)
\r
200 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
\r
201 INPUT_BUF_SIZE * SIZEOF(JOCTET));
\r
204 src = (my_src_ptr) cinfo->src;
\r
205 src->pub.init_source = init_source;
\r
206 src->pub.fill_input_buffer = fill_input_buffer;
\r
207 src->pub.skip_input_data = skip_input_data;
\r
208 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
\r
209 src->pub.term_source = term_source;
\r
210 src->infile = infile;
\r
211 src->src_size = bufsize; // FIXME ? merged from Alpha
\r
212 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
\r
213 src->pub.next_input_byte = NULL; /* until buffer loaded */
\r