3dphotoshoot

annotate libs/libjpeg/jdatasrc.c @ 17:aef7f51f6397

find changesets by author, revision, files, or words in the commit message
resource loading works
author John Tsiombikas <nuclear@member.fsf.org>
date Wed, 10 Jun 2015 06:56:27 +0300
parents
children
rev   line source
nuclear@14 1 /*
nuclear@14 2 * jdatasrc.c
nuclear@14 3 *
nuclear@14 4 * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@14 5 * This file is part of the Independent JPEG Group's software.
nuclear@14 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@14 7 *
nuclear@14 8 * This file contains decompression data source routines for the case of
nuclear@14 9 * reading JPEG data from a file (or any stdio stream). While these routines
nuclear@14 10 * are sufficient for most applications, some will want to use a different
nuclear@14 11 * source manager.
nuclear@14 12 * IMPORTANT: we assume that fread() will correctly transcribe an array of
nuclear@14 13 * JOCTETs from 8-bit-wide elements on external storage. If char is wider
nuclear@14 14 * than 8 bits on your machine, you may need to do some tweaking.
nuclear@14 15 */
nuclear@14 16
nuclear@14 17 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
nuclear@14 18 #include "jinclude.h"
nuclear@14 19 #include "jpeglib.h"
nuclear@14 20 #include "jerror.h"
nuclear@14 21
nuclear@14 22
nuclear@14 23 /* Expanded data source object for stdio input */
nuclear@14 24
nuclear@14 25 typedef struct {
nuclear@14 26 struct jpeg_source_mgr pub; /* public fields */
nuclear@14 27
nuclear@14 28 FILE * infile; /* source stream */
nuclear@14 29 JOCTET * buffer; /* start of buffer */
nuclear@14 30 boolean start_of_file; /* have we gotten any data yet? */
nuclear@14 31 } my_source_mgr;
nuclear@14 32
nuclear@14 33 typedef my_source_mgr * my_src_ptr;
nuclear@14 34
nuclear@14 35 #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
nuclear@14 36
nuclear@14 37
nuclear@14 38 /*
nuclear@14 39 * Initialize source --- called by jpeg_read_header
nuclear@14 40 * before any data is actually read.
nuclear@14 41 */
nuclear@14 42
nuclear@14 43 METHODDEF(void)
nuclear@14 44 init_source (j_decompress_ptr cinfo)
nuclear@14 45 {
nuclear@14 46 my_src_ptr src = (my_src_ptr) cinfo->src;
nuclear@14 47
nuclear@14 48 /* We reset the empty-input-file flag for each image,
nuclear@14 49 * but we don't clear the input buffer.
nuclear@14 50 * This is correct behavior for reading a series of images from one source.
nuclear@14 51 */
nuclear@14 52 src->start_of_file = TRUE;
nuclear@14 53 }
nuclear@14 54
nuclear@14 55
nuclear@14 56 /*
nuclear@14 57 * Fill the input buffer --- called whenever buffer is emptied.
nuclear@14 58 *
nuclear@14 59 * In typical applications, this should read fresh data into the buffer
nuclear@14 60 * (ignoring the current state of next_input_byte & bytes_in_buffer),
nuclear@14 61 * reset the pointer & count to the start of the buffer, and return TRUE
nuclear@14 62 * indicating that the buffer has been reloaded. It is not necessary to
nuclear@14 63 * fill the buffer entirely, only to obtain at least one more byte.
nuclear@14 64 *
nuclear@14 65 * There is no such thing as an EOF return. If the end of the file has been
nuclear@14 66 * reached, the routine has a choice of ERREXIT() or inserting fake data into
nuclear@14 67 * the buffer. In most cases, generating a warning message and inserting a
nuclear@14 68 * fake EOI marker is the best course of action --- this will allow the
nuclear@14 69 * decompressor to output however much of the image is there. However,
nuclear@14 70 * the resulting error message is misleading if the real problem is an empty
nuclear@14 71 * input file, so we handle that case specially.
nuclear@14 72 *
nuclear@14 73 * In applications that need to be able to suspend compression due to input
nuclear@14 74 * not being available yet, a FALSE return indicates that no more data can be
nuclear@14 75 * obtained right now, but more may be forthcoming later. In this situation,
nuclear@14 76 * the decompressor will return to its caller (with an indication of the
nuclear@14 77 * number of scanlines it has read, if any). The application should resume
nuclear@14 78 * decompression after it has loaded more data into the input buffer. Note
nuclear@14 79 * that there are substantial restrictions on the use of suspension --- see
nuclear@14 80 * the documentation.
nuclear@14 81 *
nuclear@14 82 * When suspending, the decompressor will back up to a convenient restart point
nuclear@14 83 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
nuclear@14 84 * indicate where the restart point will be if the current call returns FALSE.
nuclear@14 85 * Data beyond this point must be rescanned after resumption, so move it to
nuclear@14 86 * the front of the buffer rather than discarding it.
nuclear@14 87 */
nuclear@14 88
nuclear@14 89 METHODDEF(boolean)
nuclear@14 90 fill_input_buffer (j_decompress_ptr cinfo)
nuclear@14 91 {
nuclear@14 92 my_src_ptr src = (my_src_ptr) cinfo->src;
nuclear@14 93 size_t nbytes;
nuclear@14 94
nuclear@14 95 nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
nuclear@14 96
nuclear@14 97 if (nbytes <= 0) {
nuclear@14 98 if (src->start_of_file) /* Treat empty input file as fatal error */
nuclear@14 99 ERREXIT(cinfo, JERR_INPUT_EMPTY);
nuclear@14 100 WARNMS(cinfo, JWRN_JPEG_EOF);
nuclear@14 101 /* Insert a fake EOI marker */
nuclear@14 102 src->buffer[0] = (JOCTET) 0xFF;
nuclear@14 103 src->buffer[1] = (JOCTET) JPEG_EOI;
nuclear@14 104 nbytes = 2;
nuclear@14 105 }
nuclear@14 106
nuclear@14 107 src->pub.next_input_byte = src->buffer;
nuclear@14 108 src->pub.bytes_in_buffer = nbytes;
nuclear@14 109 src->start_of_file = FALSE;
nuclear@14 110
nuclear@14 111 return TRUE;
nuclear@14 112 }
nuclear@14 113
nuclear@14 114
nuclear@14 115 /*
nuclear@14 116 * Skip data --- used to skip over a potentially large amount of
nuclear@14 117 * uninteresting data (such as an APPn marker).
nuclear@14 118 *
nuclear@14 119 * Writers of suspendable-input applications must note that skip_input_data
nuclear@14 120 * is not granted the right to give a suspension return. If the skip extends
nuclear@14 121 * beyond the data currently in the buffer, the buffer can be marked empty so
nuclear@14 122 * that the next read will cause a fill_input_buffer call that can suspend.
nuclear@14 123 * Arranging for additional bytes to be discarded before reloading the input
nuclear@14 124 * buffer is the application writer's problem.
nuclear@14 125 */
nuclear@14 126
nuclear@14 127 METHODDEF(void)
nuclear@14 128 skip_input_data (j_decompress_ptr cinfo, long num_bytes)
nuclear@14 129 {
nuclear@14 130 my_src_ptr src = (my_src_ptr) cinfo->src;
nuclear@14 131
nuclear@14 132 /* Just a dumb implementation for now. Could use fseek() except
nuclear@14 133 * it doesn't work on pipes. Not clear that being smart is worth
nuclear@14 134 * any trouble anyway --- large skips are infrequent.
nuclear@14 135 */
nuclear@14 136 if (num_bytes > 0) {
nuclear@14 137 while (num_bytes > (long) src->pub.bytes_in_buffer) {
nuclear@14 138 num_bytes -= (long) src->pub.bytes_in_buffer;
nuclear@14 139 (void) fill_input_buffer(cinfo);
nuclear@14 140 /* note we assume that fill_input_buffer will never return FALSE,
nuclear@14 141 * so suspension need not be handled.
nuclear@14 142 */
nuclear@14 143 }
nuclear@14 144 src->pub.next_input_byte += (size_t) num_bytes;
nuclear@14 145 src->pub.bytes_in_buffer -= (size_t) num_bytes;
nuclear@14 146 }
nuclear@14 147 }
nuclear@14 148
nuclear@14 149
nuclear@14 150 /*
nuclear@14 151 * An additional method that can be provided by data source modules is the
nuclear@14 152 * resync_to_restart method for error recovery in the presence of RST markers.
nuclear@14 153 * For the moment, this source module just uses the default resync method
nuclear@14 154 * provided by the JPEG library. That method assumes that no backtracking
nuclear@14 155 * is possible.
nuclear@14 156 */
nuclear@14 157
nuclear@14 158
nuclear@14 159 /*
nuclear@14 160 * Terminate source --- called by jpeg_finish_decompress
nuclear@14 161 * after all data has been read. Often a no-op.
nuclear@14 162 *
nuclear@14 163 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
nuclear@14 164 * application must deal with any cleanup that should happen even
nuclear@14 165 * for error exit.
nuclear@14 166 */
nuclear@14 167
nuclear@14 168 METHODDEF(void)
nuclear@14 169 term_source (j_decompress_ptr cinfo)
nuclear@14 170 {
nuclear@14 171 /* no work necessary here */
nuclear@14 172 }
nuclear@14 173
nuclear@14 174
nuclear@14 175 /*
nuclear@14 176 * Prepare for input from a stdio stream.
nuclear@14 177 * The caller must have already opened the stream, and is responsible
nuclear@14 178 * for closing it after finishing decompression.
nuclear@14 179 */
nuclear@14 180
nuclear@14 181 GLOBAL(void)
nuclear@14 182 jpeg_stdio_src (j_decompress_ptr cinfo, FILE * infile)
nuclear@14 183 {
nuclear@14 184 my_src_ptr src;
nuclear@14 185
nuclear@14 186 /* The source object and input buffer are made permanent so that a series
nuclear@14 187 * of JPEG images can be read from the same file by calling jpeg_stdio_src
nuclear@14 188 * only before the first one. (If we discarded the buffer at the end of
nuclear@14 189 * one image, we'd likely lose the start of the next one.)
nuclear@14 190 * This makes it unsafe to use this manager and a different source
nuclear@14 191 * manager serially with the same JPEG object. Caveat programmer.
nuclear@14 192 */
nuclear@14 193 if (cinfo->src == NULL) { /* first time for this JPEG object? */
nuclear@14 194 cinfo->src = (struct jpeg_source_mgr *)
nuclear@14 195 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
nuclear@14 196 SIZEOF(my_source_mgr));
nuclear@14 197 src = (my_src_ptr) cinfo->src;
nuclear@14 198 src->buffer = (JOCTET *)
nuclear@14 199 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
nuclear@14 200 INPUT_BUF_SIZE * SIZEOF(JOCTET));
nuclear@14 201 }
nuclear@14 202
nuclear@14 203 src = (my_src_ptr) cinfo->src;
nuclear@14 204 src->pub.init_source = init_source;
nuclear@14 205 src->pub.fill_input_buffer = fill_input_buffer;
nuclear@14 206 src->pub.skip_input_data = skip_input_data;
nuclear@14 207 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
nuclear@14 208 src->pub.term_source = term_source;
nuclear@14 209 src->infile = infile;
nuclear@14 210 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
nuclear@14 211 src->pub.next_input_byte = NULL; /* until buffer loaded */
nuclear@14 212 }