www.pudn.com > imgport.rar > jmemansi.c, change:2008-11-05,size:4777b


/* 
 * 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 */ 
}