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/*
* jmemansi.c (jmemsys.c)
*
* Copyright (C) 1992, 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.
*/
#include "jinclude.h"
#include "jmemsys.h"
#ifdef INCLUDES_ARE_ANSI
#include <stdlib.h> /* to declare malloc(), free() */
#else
extern void * malloc PP((size_t size));
extern void free PP((void *ptr));
#endif
#ifndef SEEK_SET /* pre-ANSI systems may not define this; */
#define SEEK_SET 0 /* if not, assume 0 is correct */
#endif
static external_methods_ptr methods; /* saved for access to error_exit */
static long total_used; /* total memory requested so far */
/*
* Memory allocation and freeing are controlled by the regular library
* routines malloc() and free().
*/
GLOBAL void *
jget_small (size_t sizeofobject)
{
total_used += sizeofobject;
return (void *) malloc(sizeofobject);
}
GLOBAL void
jfree_small (void * object)
{
free(object);
}
/*
* We assume NEED_FAR_POINTERS is not defined and so the separate entry points
* jget_large, jfree_large are not needed.
*/
/*
* 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
jmem_available (long min_bytes_needed, long max_bytes_needed)
{
return methods->max_memory_to_use - total_used;
}
/*
* Backing store (temporary file) management.
* Backing store objects are only used when the value returned by
* jmem_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 (backing_store_ptr info, void FAR * buffer_address,
long file_offset, long byte_count)
{
if (fseek(info->temp_file, file_offset, SEEK_SET))
ERREXIT(methods, "fseek failed on temporary file");
if (JFREAD(info->temp_file, buffer_address, byte_count)
!= (size_t) byte_count)
ERREXIT(methods, "fread failed on temporary file");
}
METHODDEF void
write_backing_store (backing_store_ptr info, void FAR * buffer_address,
long file_offset, long byte_count)
{
if (fseek(info->temp_file, file_offset, SEEK_SET))
ERREXIT(methods, "fseek failed on temporary file");
if (JFWRITE(info->temp_file, buffer_address, byte_count)
!= (size_t) byte_count)
ERREXIT(methods, "fwrite failed on temporary file --- out of disk space?");
}
METHODDEF void
close_backing_store (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 temp_name[] at all;
* indeed, we can't even find out the actual name of the temp file.
*/
GLOBAL void
jopen_backing_store (backing_store_ptr info, long total_bytes_needed)
{
if ((info->temp_file = tmpfile()) == NULL)
ERREXIT(methods, "Failed to create temporary file");
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. Keep in mind that jmem_term may be called more than
* once.
*/
GLOBAL void
jmem_init (external_methods_ptr emethods)
{
methods = emethods; /* save struct addr for error exit access */
emethods->max_memory_to_use = DEFAULT_MAX_MEM;
total_used = 0;
}
GLOBAL void
jmem_term (void)
{
/* no work */
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.