/*
 * ZoneMinder JPEG memory encoding/decoding, $Date$, $Revision$
 * Copyright (C) 2003  Philip Coombes
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/ 

#include "zm_jpeg.h"

/* Expanded data destination object for memory */

typedef struct {
  struct jpeg_destination_mgr pub; /* public fields */

  JOCTET *outbuffer;		/* target buffer */
  int    *outbuffer_size;
  JOCTET *buffer;		/* start of buffer */
} mem_destination_mgr;

typedef mem_destination_mgr * mem_dest_ptr;

#define OUTPUT_BUF_SIZE  4096	/* choose an efficiently fwrite'able size */


/*
 * Initialize destination --- called by jpeg_start_compress
 * before any data is actually written.
 */

static void init_destination (j_compress_ptr cinfo)
{
  mem_dest_ptr dest = (mem_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;

  *(dest->outbuffer_size) = 0;
}


/*
 * 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.
 */

static boolean empty_output_buffer (j_compress_ptr cinfo)
{
  mem_dest_ptr dest = (mem_dest_ptr) cinfo->dest;

  memcpy( dest->outbuffer+*(dest->outbuffer_size), dest->buffer, OUTPUT_BUF_SIZE );
  *(dest->outbuffer_size) += OUTPUT_BUF_SIZE;

  dest->pub.next_output_byte = dest->buffer;
  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;

  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.
 */

static void term_destination (j_compress_ptr cinfo)
{
  mem_dest_ptr dest = (mem_dest_ptr) cinfo->dest;
  size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;

  if (datacount > 0) {
    memcpy( dest->outbuffer+*(dest->outbuffer_size), dest->buffer, datacount );
    *(dest->outbuffer_size) += datacount;
  }
}


/*
 * Prepare for output to a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing compression.
 */

void jpeg_mem_dest (j_compress_ptr cinfo, JOCTET *outbuffer, int *outbuffer_size )
{
  mem_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(mem_destination_mgr));
  }

  dest = (mem_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->outbuffer = outbuffer;
  dest->outbuffer_size = outbuffer_size;
}

/* Expanded data source object for memory input */

typedef struct {
  struct jpeg_source_mgr pub;	/* public fields */

  JOCTET * inbuffer;		/* source stream */
  int    inbuffer_size;

  JOCTET * buffer;		/* start of buffer */
  boolean start_of_data;	/* have we gotten any data yet? */
} mem_source_mgr;

typedef mem_source_mgr * mem_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.
 */

static void init_source (j_decompress_ptr cinfo)
{
  mem_src_ptr src = (mem_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_data = TRUE;
  src->pub.bytes_in_buffer = 0;
}


/*
 * 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.
 */

static boolean fill_input_buffer (j_decompress_ptr cinfo)
{
  mem_src_ptr src = (mem_src_ptr) cinfo->src;
  size_t nbytes;

  memcpy( src->buffer, src->inbuffer, (size_t) src->inbuffer_size );
  nbytes = src->inbuffer_size;

  if (nbytes <= 0) {
    if (src->start_of_data)	/* 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_data = FALSE;

  return TRUE;
}


/*
 * 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.
 */

static void skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
  mem_src_ptr src = (mem_src_ptr) 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->pub.bytes_in_buffer) {
      num_bytes -= (long) src->pub.bytes_in_buffer;
      (void) fill_input_buffer(cinfo);
      /* note we assume that fill_input_buffer will never return FALSE,
       * so suspension need not be handled.
       */
    }
    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 */
}


/*
 * Prepare for input from a memory stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing decompression.
 */

void jpeg_mem_src (j_decompress_ptr cinfo, JOCTET *inbuffer, int inbuffer_size )
{
  mem_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_mem_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(mem_source_mgr));
    src = (mem_src_ptr) cinfo->src;
    src->buffer = (JOCTET *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				  inbuffer_size * SIZEOF(JOCTET));
  }

  src = (mem_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->inbuffer = inbuffer;
  src->inbuffer_size = inbuffer_size;
  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
  src->pub.next_input_byte = NULL; /* until buffer loaded */
}