The Tor Browser: media/libjpeg/jdatasrc.c@b8a032363ba2 (annotated)

media/libjpeg/jdatasrc.c@b8a032363ba2 (annotated)

media/libjpeg/jdatasrc.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * jdatasrc.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * Modified 2009-2011 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2013, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains decompression data source routines for the case of
  * reading JPEG data from memory or from a file (or any stdio stream).
  * While these routines are sufficient for most applications,
  * some will want to use a different source manager.
  * IMPORTANT: we assume that fread() will correctly transcribe an array of
  * JOCTETs from 8-bit-wide elements on external storage.  If char is wider
  * than 8 bits on your machine, you may need to do some tweaking.
  */
 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jerror.h"
 /* Expanded data source object for stdio input */
 typedef struct {
   struct jpeg_source_mgr pub;	/* public fields */
   FILE * infile;		/* source stream */
   JOCTET * buffer;		/* start of buffer */
   boolean start_of_file;	/* have we gotten any data yet? */
 } my_source_mgr;
 typedef my_source_mgr * my_src_ptr;
 #define INPUT_BUF_SIZE  4096	/* choose an efficiently fread'able size */
 /*
  * Initialize source --- called by jpeg_read_header
  * before any data is actually read.
  */
 METHODDEF(void)
 init_source (j_decompress_ptr cinfo)
 {
   my_src_ptr src = (my_src_ptr) cinfo->src;
   /* We reset the empty-input-file flag for each image,
    * but we don't clear the input buffer.
    * This is correct behavior for reading a series of images from one source.
    */
   src->start_of_file = TRUE;
 }
 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
 METHODDEF(void)
 init_mem_source (j_decompress_ptr cinfo)
 {
   /* no work necessary here */
 }
 #endif
 /*
  * Fill the input buffer --- called whenever buffer is emptied.
  *
  * In typical applications, this should read fresh data into the buffer
  * (ignoring the current state of next_input_byte & bytes_in_buffer),
  * reset the pointer & count to the start of the buffer, and return TRUE
  * indicating that the buffer has been reloaded.  It is not necessary to
  * fill the buffer entirely, only to obtain at least one more byte.
  *
  * There is no such thing as an EOF return.  If the end of the file has been
  * reached, the routine has a choice of ERREXIT() or inserting fake data into
  * the buffer.  In most cases, generating a warning message and inserting a
  * fake EOI marker is the best course of action --- this will allow the
  * decompressor to output however much of the image is there.  However,
  * the resulting error message is misleading if the real problem is an empty
  * input file, so we handle that case specially.
  *
  * In applications that need to be able to suspend compression due to input
  * not being available yet, a FALSE return indicates that no more data can be
  * obtained right now, but more may be forthcoming later.  In this situation,
  * the decompressor will return to its caller (with an indication of the
  * number of scanlines it has read, if any).  The application should resume
  * decompression after it has loaded more data into the input buffer.  Note
  * that there are substantial restrictions on the use of suspension --- see
  * the documentation.
  *
  * When suspending, the decompressor will back up to a convenient restart point
  * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
  * indicate where the restart point will be if the current call returns FALSE.
  * Data beyond this point must be rescanned after resumption, so move it to
  * the front of the buffer rather than discarding it.
  */
 METHODDEF(boolean)
 fill_input_buffer (j_decompress_ptr cinfo)
 {
   my_src_ptr src = (my_src_ptr) cinfo->src;
   size_t nbytes;
   nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
   if (nbytes <= 0) {
     if (src->start_of_file)	/* Treat empty input file as fatal error */
       ERREXIT(cinfo, JERR_INPUT_EMPTY);
     WARNMS(cinfo, JWRN_JPEG_EOF);
     /* Insert a fake EOI marker */
     src->buffer[0] = (JOCTET) 0xFF;
     src->buffer[1] = (JOCTET) JPEG_EOI;
     nbytes = 2;
   }
   src->pub.next_input_byte = src->buffer;
   src->pub.bytes_in_buffer = nbytes;
   src->start_of_file = FALSE;
   return TRUE;
 }
 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
 METHODDEF(boolean)
 fill_mem_input_buffer (j_decompress_ptr cinfo)
 {
   static const JOCTET mybuffer[4] = {
     (JOCTET) 0xFF, (JOCTET) JPEG_EOI, 0, 0
   };
   /* The whole JPEG data is expected to reside in the supplied memory
    * buffer, so any request for more data beyond the given buffer size
    * is treated as an error.
    */
   WARNMS(cinfo, JWRN_JPEG_EOF);
   /* Insert a fake EOI marker */
   cinfo->src->next_input_byte = mybuffer;
   cinfo->src->bytes_in_buffer = 2;
   return TRUE;
 }
 #endif
 /*
  * Skip data --- used to skip over a potentially large amount of
  * uninteresting data (such as an APPn marker).
  *
  * Writers of suspendable-input applications must note that skip_input_data
  * is not granted the right to give a suspension return.  If the skip extends
  * beyond the data currently in the buffer, the buffer can be marked empty so
  * that the next read will cause a fill_input_buffer call that can suspend.
  * Arranging for additional bytes to be discarded before reloading the input
  * buffer is the application writer's problem.
  */
 METHODDEF(void)
 skip_input_data (j_decompress_ptr cinfo, long num_bytes)
 {
   struct jpeg_source_mgr * src = cinfo->src;
   /* Just a dumb implementation for now.  Could use fseek() except
    * it doesn't work on pipes.  Not clear that being smart is worth
    * any trouble anyway --- large skips are infrequent.
    */
   if (num_bytes > 0) {
     while (num_bytes > (long) src->bytes_in_buffer) {
       num_bytes -= (long) src->bytes_in_buffer;
       (void) (*src->fill_input_buffer) (cinfo);
       /* note we assume that fill_input_buffer will never return FALSE,
        * so suspension need not be handled.
        */
     }
     src->next_input_byte += (size_t) num_bytes;
     src->bytes_in_buffer -= (size_t) num_bytes;
   }
 }
 /*
  * An additional method that can be provided by data source modules is the
  * resync_to_restart method for error recovery in the presence of RST markers.
  * For the moment, this source module just uses the default resync method
  * provided by the JPEG library.  That method assumes that no backtracking
  * is possible.
  */
 /*
  * Terminate source --- called by jpeg_finish_decompress
  * after all data has been read.  Often a no-op.
  *
  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
  * application must deal with any cleanup that should happen even
  * for error exit.
  */
 METHODDEF(void)
 term_source (j_decompress_ptr cinfo)
 {
   /* no work necessary here */
 }
 /*
  * Prepare for input from a stdio stream.
  * The caller must have already opened the stream, and is responsible
  * for closing it after finishing decompression.
  */
 GLOBAL(void)
 jpeg_stdio_src (j_decompress_ptr cinfo, FILE * infile)
 {
   my_src_ptr src;
   /* The source object and input buffer are made permanent so that a series
    * of JPEG images can be read from the same file by calling jpeg_stdio_src
    * only before the first one.  (If we discarded the buffer at the end of
    * one image, we'd likely lose the start of the next one.)
    * This makes it unsafe to use this manager and a different source
    * manager serially with the same JPEG object.  Caveat programmer.
    */
   if (cinfo->src == NULL) {	/* first time for this JPEG object? */
     cinfo->src = (struct jpeg_source_mgr *)
       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 				  SIZEOF(my_source_mgr));
     src = (my_src_ptr) cinfo->src;
     src->buffer = (JOCTET *)
       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 				  INPUT_BUF_SIZE * SIZEOF(JOCTET));
   }
   src = (my_src_ptr) cinfo->src;
   src->pub.init_source = init_source;
   src->pub.fill_input_buffer = fill_input_buffer;
   src->pub.skip_input_data = skip_input_data;
   src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
   src->pub.term_source = term_source;
   src->infile = infile;
   src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
   src->pub.next_input_byte = NULL; /* until buffer loaded */
 }
 #if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
 /*
  * Prepare for input from a supplied memory buffer.
  * The buffer must contain the whole JPEG data.
  */
 GLOBAL(void)
 jpeg_mem_src (j_decompress_ptr cinfo,
 	      unsigned char * inbuffer, unsigned long insize)
 {
   struct jpeg_source_mgr * src;
   if (inbuffer == NULL || insize == 0)	/* Treat empty input as fatal error */
     ERREXIT(cinfo, JERR_INPUT_EMPTY);
   /* The source object is made permanent so that a series of JPEG images
    * can be read from the same buffer by calling jpeg_mem_src only before
    * the first one.
    */
   if (cinfo->src == NULL) {	/* first time for this JPEG object? */
     cinfo->src = (struct jpeg_source_mgr *)
       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 				  SIZEOF(struct jpeg_source_mgr));
   }
   src = cinfo->src;
   src->init_source = init_mem_source;
   src->fill_input_buffer = fill_mem_input_buffer;
   src->skip_input_data = skip_input_data;
   src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
   src->term_source = term_source;
   src->bytes_in_buffer = (size_t) insize;
   src->next_input_byte = (JOCTET *) inbuffer;
 }
 #endif

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media/libjpeg/jdatasrc.c@b8a032363ba2 (annotated)

media/libjpeg/jdatasrc.c