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  * libjpeg-turbo Modifications:
   8  * Copyright (C) 2013, 2016, 2022, D. R. Commander.
   9  * For conditions of distribution and use, see the accompanying README.ijg
  10  * file.
  11  *
  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.
  19  */
  20
  21 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
  22 #include "jinclude.h"
  23 #include "jpeglib.h"
  24 #include "jerror.h"
  25
  26
  27 /* Expanded data source object for stdio input */
  28
  29 typedef struct {
  30   struct jpeg_source_mgr pub;   /* public fields */
  31
  32   FILE *infile;                 /* source stream */
  33   JOCTET *buffer;               /* start of buffer */
  34   boolean start_of_file;        /* have we gotten any data yet? */
  35 } my_source_mgr;
  36
  37 typedef my_source_mgr *my_src_ptr;
  38
  39 #define INPUT_BUF_SIZE  4096    /* choose an efficiently fread'able size */
  40
  41
  42 /*
  43  * Initialize source --- called by jpeg_read_header
  44  * before any data is actually read.
  45  */
  46
  47 METHODDEF(void)
  48 init_source(j_decompress_ptr cinfo)
  49 {
  50   my_src_ptr src = (my_src_ptr)cinfo->src;
  51
  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.
  55    */
  56   src->start_of_file = TRUE;
  57 }
  58
  59 METHODDEF(void)
  60 init_mem_source(j_decompress_ptr cinfo)
  61 {
  62   /* no work necessary here */
  63 }
  64
  65
  66 /*
  67  * Fill the input buffer --- called whenever buffer is emptied.
  68  *
  69  * In typical applications, this should read fresh data into the buffer
  70  * (ignoring the current state of next_input_byte & bytes_in_buffer),
  71  * reset the pointer & count to the start of the buffer, and return TRUE
  72  * indicating that the buffer has been reloaded.  It is not necessary to
  73  * fill the buffer entirely, only to obtain at least one more byte.
  74  *
  75  * There is no such thing as an EOF return.  If the end of the file has been
  76  * reached, the routine has a choice of ERREXIT() or inserting fake data into
  77  * the buffer.  In most cases, generating a warning message and inserting a
  78  * fake EOI marker is the best course of action --- this will allow the
  79  * decompressor to output however much of the image is there.  However,
  80  * the resulting error message is misleading if the real problem is an empty
  81  * input file, so we handle that case specially.
  82  *
  83  * In applications that need to be able to suspend compression due to input
  84  * not being available yet, a FALSE return indicates that no more data can be
  85  * obtained right now, but more may be forthcoming later.  In this situation,
  86  * the decompressor will return to its caller (with an indication of the
  87  * number of scanlines it has read, if any).  The application should resume
  88  * decompression after it has loaded more data into the input buffer.  Note
  89  * that there are substantial restrictions on the use of suspension --- see
  90  * the documentation.
  91  *
  92  * When suspending, the decompressor will back up to a convenient restart point
  93  * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
  94  * indicate where the restart point will be if the current call returns FALSE.
  95  * Data beyond this point must be rescanned after resumption, so move it to
  96  * the front of the buffer rather than discarding it.
  97  */
  98
  99 METHODDEF(boolean)
 100 fill_input_buffer(j_decompress_ptr cinfo)
 101 {
 102   my_src_ptr src = (my_src_ptr)cinfo->src;
 103   size_t nbytes;
 104
 105   nbytes = fread(src->buffer, 1, INPUT_BUF_SIZE, src->infile);
 106
 107   if (nbytes <= 0) {
 108     if (src->start_of_file)     /* Treat empty input file as fatal error */
 109       ERREXIT(cinfo, JERR_INPUT_EMPTY);
 110     WARNMS(cinfo, JWRN_JPEG_EOF);
 111     /* Insert a fake EOI marker */
 112     src->buffer[0] = (JOCTET)0xFF;
 113     src->buffer[1] = (JOCTET)JPEG_EOI;
 114     nbytes = 2;
 115   }
 116
 117   src->pub.next_input_byte = src->buffer;
 118   src->pub.bytes_in_buffer = nbytes;
 119   src->start_of_file = FALSE;
 120
 121   return TRUE;
 122 }
 123
 124 METHODDEF(boolean)
 125 fill_mem_input_buffer(j_decompress_ptr cinfo)
 126 {
 127   static const JOCTET mybuffer[4] = {
 128     (JOCTET)0xFF, (JOCTET)JPEG_EOI, 0, 0
 129   };
 130
 131   /* The whole JPEG data is expected to reside in the supplied memory
 132    * buffer, so any request for more data beyond the given buffer size
 133    * is treated as an error.
 134    */
 135   WARNMS(cinfo, JWRN_JPEG_EOF);
 136
 137   /* Insert a fake EOI marker */
 138
 139   cinfo->src->next_input_byte = mybuffer;
 140   cinfo->src->bytes_in_buffer = 2;
 141
 142   return TRUE;
 143 }
 144
 145
 146 /*
 147  * Skip data --- used to skip over a potentially large amount of
 148  * uninteresting data (such as an APPn marker).
 149  *
 150  * Writers of suspendable-input applications must note that skip_input_data
 151  * is not granted the right to give a suspension return.  If the skip extends
 152  * beyond the data currently in the buffer, the buffer can be marked empty so
 153  * that the next read will cause a fill_input_buffer call that can suspend.
 154  * Arranging for additional bytes to be discarded before reloading the input
 155  * buffer is the application writer's problem.
 156  */
 157
 158 METHODDEF(void)
 159 skip_input_data(j_decompress_ptr cinfo, long num_bytes)
 160 {
 161   struct jpeg_source_mgr *src = cinfo->src;
 162
 163   /* Just a dumb implementation for now.  Could use fseek() except
 164    * it doesn't work on pipes.  Not clear that being smart is worth
 165    * any trouble anyway --- large skips are infrequent.
 166    */
 167   if (num_bytes > 0) {
 168     while (num_bytes > (long)src->bytes_in_buffer) {
 169       num_bytes -= (long)src->bytes_in_buffer;
 170       (void)(*src->fill_input_buffer) (cinfo);
 171       /* note we assume that fill_input_buffer will never return FALSE,
 172        * so suspension need not be handled.
 173        */
 174     }
 175     src->next_input_byte += (size_t)num_bytes;
 176     src->bytes_in_buffer -= (size_t)num_bytes;
 177   }
 178 }
 179
 180
 181 /*
 182  * An additional method that can be provided by data source modules is the
 183  * resync_to_restart method for error recovery in the presence of RST markers.
 184  * For the moment, this source module just uses the default resync method
 185  * provided by the JPEG library.  That method assumes that no backtracking
 186  * is possible.
 187  */
 188
 189
 190 /*
 191  * Terminate source --- called by jpeg_finish_decompress
 192  * after all data has been read.  Often a no-op.
 193  *
 194  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
 195  * application must deal with any cleanup that should happen even
 196  * for error exit.
 197  */
 198
 199 METHODDEF(void)
 200 term_source(j_decompress_ptr cinfo)
 201 {
 202   /* no work necessary here */
 203 }
 204
 205
 206 /*
 207  * Prepare for input from a stdio stream.
 208  * The caller must have already opened the stream, and is responsible
 209  * for closing it after finishing decompression.
 210  */
 211
 212 GLOBAL(void)
 213 jpeg_stdio_src(j_decompress_ptr cinfo, FILE *infile)
 214 {
 215   my_src_ptr src;
 216
 217   /* The source object and input buffer are made permanent so that a series
 218    * of JPEG images can be read from the same file by calling jpeg_stdio_src
 219    * only before the first one.  (If we discarded the buffer at the end of
 220    * one image, we'd likely lose the start of the next one.)
 221    */
 222   if (cinfo->src == NULL) {     /* first time for this JPEG object? */
 223     cinfo->src = (struct jpeg_source_mgr *)
 224       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
 225                                   sizeof(my_source_mgr));
 226     src = (my_src_ptr)cinfo->src;
 227     src->buffer = (JOCTET *)
 228       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
 229                                   INPUT_BUF_SIZE * sizeof(JOCTET));
 230   } else if (cinfo->src->init_source != init_source) {
 231     /* It is unsafe to reuse the existing source manager unless it was created
 232      * by this function.  Otherwise, there is no guarantee that the opaque
 233      * structure is the right size.  Note that we could just create a new
 234      * structure, but the old structure would not be freed until
 235      * jpeg_destroy_decompress() was called.
 236      */
 237     ERREXIT(cinfo, JERR_BUFFER_SIZE);
 238   }
 239
 240   src = (my_src_ptr)cinfo->src;
 241   src->pub.init_source = init_source;
 242   src->pub.fill_input_buffer = fill_input_buffer;
 243   src->pub.skip_input_data = skip_input_data;
 244   src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
 245   src->pub.term_source = term_source;
 246   src->infile = infile;
 247   src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
 248   src->pub.next_input_byte = NULL; /* until buffer loaded */
 249 }
 250
 251
 252 /*
 253  * Prepare for input from a supplied memory buffer.
 254  * The buffer must contain the whole JPEG data.
 255  */
 256
 257 GLOBAL(void)
 258 jpeg_mem_src(j_decompress_ptr cinfo, const unsigned char *inbuffer,
 259              unsigned long insize)
 260 {
 261   struct jpeg_source_mgr *src;
 262
 263   if (inbuffer == NULL || insize == 0)  /* Treat empty input as fatal error */
 264     ERREXIT(cinfo, JERR_INPUT_EMPTY);
 265
 266   /* The source object is made permanent so that a series of JPEG images
 267    * can be read from the same buffer by calling jpeg_mem_src only before
 268    * the first one.
 269    */
 270   if (cinfo->src == NULL) {     /* first time for this JPEG object? */
 271     cinfo->src = (struct jpeg_source_mgr *)
 272       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
 273                                   sizeof(struct jpeg_source_mgr));
 274   } else if (cinfo->src->init_source != init_mem_source) {
 275     /* It is unsafe to reuse the existing source manager unless it was created
 276      * by this function.
 277      */
 278     ERREXIT(cinfo, JERR_BUFFER_SIZE);
 279   }
 280
 281   src = cinfo->src;
 282   src->init_source = init_mem_source;
 283   src->fill_input_buffer = fill_mem_input_buffer;
 284   src->skip_input_data = skip_input_data;
 285   src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
 286   src->term_source = term_source;
 287   src->bytes_in_buffer = (size_t)insize;
 288   src->next_input_byte = (const JOCTET *)inbuffer;
 289 }