/*
    Copyright (C) 1998 by Tor Andersson and Jorrit Tyberghein

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/* !!! not standard... written by Tor Andersson !!!
 * get data from memory buffer instead of from file
 * assumes that the entire file is in one large block of memory
 *
 */

/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
#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;


/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */

static 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;
}


/*
 * Fill the input buffer --- called whenever buffer is emptied.
 * should never happen :)
 */

static boolean
fill_input_buffer (j_decompress_ptr cinfo)
{
  /* no-op */ (void)cinfo;
 return TRUE;
}


/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 */

static void
skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;

  if (num_bytes > 0) {
    src->pub.next_input_byte += (size_t) num_bytes;
    src->pub.bytes_in_buffer -= (size_t) num_bytes;
  }
}


/*
 * 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.
 */

static void
term_source (j_decompress_ptr cinfo)
{
  /* no work necessary here */ (void)cinfo;
}


/*
 * Prepare for input from mem buffer.
 * Leaves buffer untouched.
 */

void
jpeg_memory_src (j_decompress_ptr cinfo, char * inbfr, int len)
{
  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,
				  (size_t)sizeof(my_source_mgr));
    src = (my_src_ptr) cinfo->src;
    src->buffer = (JOCTET *) inbfr;
  }

  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 = 0L;
  src->pub.bytes_in_buffer = len;		/*!!! sets to entire file len */
  src->pub.next_input_byte = (JOCTET *)inbfr;	/*!!! at start of buffer */
}

