/*

 * jmemansi.c

 *

 * Copyright (C) 1992-1996, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file provides a simple generic implementation of the system-

 * dependent portion of the JPEG memory manager.  This implementation

 * assumes that you have the ANSI-standard library routine tmpfile().

 * Also, the problem of determining the amount of memory available

 * is shoved onto the user.

 */



#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jmemsys.h"		/* import the system-dependent declarations */



#ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare malloc(),free() */

extern void * malloc JPP((size_t size));

extern void free JPP((void *ptr));

#endif



#ifndef SEEK_SET		/* pre-ANSI systems may not define this; */

#define SEEK_SET  0		/* if not, assume 0 is correct */

#endif





/*

 * Memory allocation and freeing are controlled by the regular library

 * routines malloc() and free().

 */



GLOBAL(void *)

jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)

{

  return (void *) malloc(sizeofobject);

}



GLOBAL(void)

jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)

{

  free(object);

}





/*

 * "Large" objects are treated the same as "small" ones.

 * NB: although we include FAR keywords in the routine declarations,

 * this file won't actually work in 80x86 small/medium model; at least,

 * you probably won't be able to process useful-size images in only 64KB.

 */



GLOBAL(void FAR *)

jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)

{

  return (void FAR *) malloc(sizeofobject);

}



GLOBAL(void)

jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)

{

  free(object);

}





/*

 * This routine computes the total memory space available for allocation.

 * It's impossible to do this in a portable way; our current solution is

 * to make the user tell us (with a default value set at compile time).

 * If you can actually get the available space, it's a good idea to subtract

 * a slop factor of 5% or so.

 */



#ifndef DEFAULT_MAX_MEM		/* so can override from makefile */

#define DEFAULT_MAX_MEM		1000000L /* default: one megabyte */

#endif



GLOBAL(long)

jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,

		    long max_bytes_needed, long already_allocated)

{

  return cinfo->mem->max_memory_to_use - already_allocated;

}





/*

 * Backing store (temporary file) management.

 * Backing store objects are only used when the value returned by

 * jpeg_mem_available is less than the total space needed.  You can dispense

 * with these routines if you have plenty of virtual memory; see jmemnobs.c.

 */





METHODDEF(void)

read_backing_store (j_common_ptr cinfo, backing_store_ptr info,

		    void FAR * buffer_address,

		    long file_offset, long byte_count)

{

  if (fseek(info->temp_file, file_offset, SEEK_SET))

    ERREXIT(cinfo, JERR_TFILE_SEEK);

  if (JFREAD(info->temp_file, buffer_address, byte_count)

      != (size_t) byte_count)

    ERREXIT(cinfo, JERR_TFILE_READ);

}





METHODDEF(void)

write_backing_store (j_common_ptr cinfo, backing_store_ptr info,

		     void FAR * buffer_address,

		     long file_offset, long byte_count)

{

  if (fseek(info->temp_file, file_offset, SEEK_SET))

    ERREXIT(cinfo, JERR_TFILE_SEEK);

  if (JFWRITE(info->temp_file, buffer_address, byte_count)

      != (size_t) byte_count)

    ERREXIT(cinfo, JERR_TFILE_WRITE);

}





METHODDEF(void)

close_backing_store (j_common_ptr cinfo, backing_store_ptr info)

{

  fclose(info->temp_file);

  /* Since this implementation uses tmpfile() to create the file,

   * no explicit file deletion is needed.

   */

}





/*

 * Initial opening of a backing-store object.

 *

 * This version uses tmpfile(), which constructs a suitable file name

 * behind the scenes.  We don't have to use info->temp_name[] at all;

 * indeed, we can't even find out the actual name of the temp file.

 */



GLOBAL(void)

jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,

			 long total_bytes_needed)

{

  if ((info->temp_file = tmpfile()) == NULL)

    ERREXITS(cinfo, JERR_TFILE_CREATE, "");

  info->read_backing_store = read_backing_store;

  info->write_backing_store = write_backing_store;

  info->close_backing_store = close_backing_store;

}





/*

 * These routines take care of any system-dependent initialization and

 * cleanup required.

 */



GLOBAL(long)

jpeg_mem_init (j_common_ptr cinfo)

{

  return DEFAULT_MAX_MEM;	/* default for max_memory_to_use */

}



GLOBAL(void)

jpeg_mem_term (j_common_ptr cinfo)

{

  /* no work */

}

