jdatadst.c

Go to the documentation of this file.

/*
 * jdatadst.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Modified 2009-2019 by Guido Vollbeding.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains compression data destination routines for the case of
 * emitting JPEG data to memory or to a file (or any stdio stream).
 * While these routines are sufficient for most applications,
 * some will want to use a different destination manager.
 * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
 * JOCTETs into 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"
 
#ifndef HAVE_STDLIB_H       /* <stdlib.h> should declare malloc(),free() */
extern void * malloc JPP((size_t size));
extern void free JPP((void *ptr));
#endif
 
 
/* Expanded data destination object for stdio output */
 
typedef struct {
  struct jpeg_destination_mgr pub; /* public fields */
 
  FILE * outfile;       /* target stream */
  JOCTET * buffer;      /* start of buffer */
} my_destination_mgr;
 
typedef my_destination_mgr * my_dest_ptr;
 
#define OUTPUT_BUF_SIZE  4096   /* choose an efficiently fwrite'able size */
 
 
/* Expanded data destination object for memory output */
 
typedef struct {
  struct jpeg_destination_mgr pub; /* public fields */
 
  unsigned char ** outbuffer;   /* target buffer */
  size_t * outsize;
  unsigned char * newbuffer;    /* newly allocated buffer */
  JOCTET * buffer;      /* start of buffer */
  size_t bufsize;
} my_mem_destination_mgr;
 
typedef my_mem_destination_mgr * my_mem_dest_ptr;
 
 
/*
 * Initialize destination --- called by jpeg_start_compress
 * before any data is actually written.
 */
 
METHODDEF(void)
init_destination (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
 
  /* Allocate the output buffer --- it will be released when done with image */
  dest->buffer = (JOCTET *) (*cinfo->mem->alloc_small)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
 
  dest->pub.next_output_byte = dest->buffer;
  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
}
 
METHODDEF(void)
init_mem_destination (j_compress_ptr cinfo)
{
  /* no work necessary here */
}
 
 
/*
 * Empty the output buffer --- called whenever buffer fills up.
 *
 * In typical applications, this should write the entire output buffer
 * (ignoring the current state of next_output_byte & free_in_buffer),
 * reset the pointer & count to the start of the buffer, and return TRUE
 * indicating that the buffer has been dumped.
 *
 * In applications that need to be able to suspend compression due to output
 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
 * In this situation, the compressor will return to its caller (possibly with
 * an indication that it has not accepted all the supplied scanlines).  The
 * application should resume compression after it has made more room in the
 * output buffer.  Note that there are substantial restrictions on the use of
 * suspension --- see the documentation.
 *
 * When suspending, the compressor will back up to a convenient restart point
 * (typically the start of the current MCU). next_output_byte & free_in_buffer
 * indicate where the restart point will be if the current call returns FALSE.
 * Data beyond this point will be regenerated after resumption, so do not
 * write it out when emptying the buffer externally.
 */
 
METHODDEF(boolean)
empty_output_buffer (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
 
  if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
      (size_t) OUTPUT_BUF_SIZE)
    ERREXIT(cinfo, JERR_FILE_WRITE);
 
  dest->pub.next_output_byte = dest->buffer;
  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
 
  return TRUE;
}
 
METHODDEF(boolean)
empty_mem_output_buffer (j_compress_ptr cinfo)
{
  size_t nextsize;
  JOCTET * nextbuffer;
  my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
 
  /* Try to allocate new buffer with double size */
  nextsize = dest->bufsize * 2;
  nextbuffer = (JOCTET *) malloc(nextsize);
 
  if (nextbuffer == NULL)
    ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 11);
 
  MEMCOPY(nextbuffer, dest->buffer, dest->bufsize);
 
  if (dest->newbuffer != NULL)
    free(dest->newbuffer);
 
  dest->newbuffer = nextbuffer;
 
  dest->pub.next_output_byte = nextbuffer + dest->bufsize;
  dest->pub.free_in_buffer = dest->bufsize;
 
  dest->buffer = nextbuffer;
  dest->bufsize = nextsize;
 
  return TRUE;
}
 
 
/*
 * Terminate destination --- called by jpeg_finish_compress
 * after all data has been written.  Usually needs to flush buffer.
 *
 * 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_destination (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
  size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
 
  /* Write any data remaining in the buffer */
  if (datacount > 0) {
    if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
      ERREXIT(cinfo, JERR_FILE_WRITE);
  }
  JFFLUSH(dest->outfile);
  /* Make sure we wrote the output file OK */
  if (JFERROR(dest->outfile))
    ERREXIT(cinfo, JERR_FILE_WRITE);
}
 
METHODDEF(void)
term_mem_destination (j_compress_ptr cinfo)
{
  my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
 
  *dest->outbuffer = dest->buffer;
  *dest->outsize = dest->bufsize - dest->pub.free_in_buffer;
}
 
 
/*
 * Prepare for output to a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing compression.
 */
 
GLOBAL(void)
jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile)
{
  my_dest_ptr dest;
 
  /* The destination object is made permanent so that multiple JPEG images
   * can be written to the same file without re-executing jpeg_stdio_dest.
   * This makes it dangerous to use this manager and a different destination
   * manager serially with the same JPEG object, because their private object
   * sizes may be different.  Caveat programmer.
   */
  if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
    cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small)
      ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(my_destination_mgr));
  }
 
  dest = (my_dest_ptr) cinfo->dest;
  dest->pub.init_destination = init_destination;
  dest->pub.empty_output_buffer = empty_output_buffer;
  dest->pub.term_destination = term_destination;
  dest->outfile = outfile;
}
 
 
/*
 * Prepare for output to a memory buffer.
 * The caller may supply an own initial buffer with appropriate size.
 * Otherwise, or when the actual data output exceeds the given size,
 * the library adapts the buffer size as necessary.
 * The standard library functions malloc/free are used for allocating
 * larger memory, so the buffer is available to the application after
 * finishing compression, and then the application is responsible for
 * freeing the requested memory.
 * Note:  An initial buffer supplied by the caller is expected to be
 * managed by the application.  The library does not free such buffer
 * when allocating a larger buffer.
 */
 
GLOBAL(void)
jpeg_mem_dest (j_compress_ptr cinfo,
           unsigned char ** outbuffer, size_t * outsize)
{
  my_mem_dest_ptr dest;
 
  if (outbuffer == NULL || outsize == NULL) /* sanity check */
    ERREXIT(cinfo, JERR_BUFFER_SIZE);
 
  /* The destination object is made permanent so that multiple JPEG images
   * can be written to the same buffer without re-executing jpeg_mem_dest.
   */
  if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
    cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small)
      ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(my_mem_destination_mgr));
  }
 
  dest = (my_mem_dest_ptr) cinfo->dest;
  dest->pub.init_destination = init_mem_destination;
  dest->pub.empty_output_buffer = empty_mem_output_buffer;
  dest->pub.term_destination = term_mem_destination;
  dest->outbuffer = outbuffer;
  dest->outsize = outsize;
  dest->newbuffer = NULL;
 
  if (*outbuffer == NULL || *outsize == 0) {
    /* Allocate initial buffer */
    dest->newbuffer = *outbuffer = (unsigned char *) malloc(OUTPUT_BUF_SIZE);
    if (dest->newbuffer == NULL)
      ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
    *outsize = OUTPUT_BUF_SIZE;
  }
 
  dest->pub.next_output_byte = dest->buffer = *outbuffer;
  dest->pub.free_in_buffer = dest->bufsize = *outsize;
}