media/libjpeg/jdatasrc.c

   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  * 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
  28 typedef 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
  36 typedef 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
  46 METHODDEF(void)
  47 init_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)
  59 METHODDEF(void)
  60 init_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
 100 METHODDEF(boolean)
 101 fill_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)
 126 METHODDEF(boolean)
 127 fill_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
 161 METHODDEF(void)
 162 skip_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
 202 METHODDEF(void)
 203 term_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
 215 GLOBAL(void)
 216 jpeg_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
 255 GLOBAL(void)
 256 jpeg_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