www.pudn.com > imgport.rar > jmemname.c, change:2008-11-05,size:8590b


/* 
 * jmemname.c 
 * 
 * Copyright (C) 1992-1997, 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 generic implementation of the system-dependent 
 * portion of the JPEG memory manager.  This implementation assumes that 
 * you must explicitly construct a name for each temp file. 
 * 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 
 
#ifdef DONT_USE_B_MODE		/* define mode parameters for fopen() */ 
#define READ_BINARY	"r" 
#define RW_BINARY	"w+" 
#else 
#ifdef VMS			/* VMS is very nonstandard */ 
#define READ_BINARY	"rb", "ctx=stm" 
#define RW_BINARY	"w+b", "ctx=stm" 
#else				/* standard ANSI-compliant case */ 
#define READ_BINARY	"rb" 
#define RW_BINARY	"w+b" 
#endif 
#endif 
 
 
/* 
 * Selection of a file name for a temporary file. 
 * This is system-dependent! 
 * 
 * The code as given is suitable for most Unix systems, and it is easily 
 * modified for most non-Unix systems.  Some notes: 
 *  1.  The temp file is created in the directory named by TEMP_DIRECTORY. 
 *      The default value is /usr/tmp, which is the conventional place for 
 *      creating large temp files on Unix.  On other systems you'll probably 
 *      want to change the file location.  You can do this by editing the 
 *      #define, or (preferred) by defining TEMP_DIRECTORY in jconfig.h. 
 * 
 *  2.  If you need to change the file name as well as its location, 
 *      you can override the TEMP_FILE_NAME macro.  (Note that this is 
 *      actually a printf format string; it must contain %s and %d.) 
 *      Few people should need to do this. 
 * 
 *  3.  mktemp() is used to ensure that multiple processes running 
 *      simultaneously won't select the same file names.  If your system 
 *      doesn't have mktemp(), define NO_MKTEMP to do it the hard way. 
 *      (If you don't have <errno.h>, also define NO_ERRNO_H.) 
 * 
 *  4.  You probably want to define NEED_SIGNAL_CATCHER so that cjpeg.c/djpeg.c 
 *      will cause the temp files to be removed if you stop the program early. 
 */ 
 
#ifndef TEMP_DIRECTORY		/* can override from jconfig.h or Makefile */ 
#define TEMP_DIRECTORY  "/usr/tmp/" /* recommended setting for Unix */ 
#endif 
 
static int next_file_num;	/* to distinguish among several temp files */ 
 
#ifdef NO_MKTEMP 
 
#ifndef TEMP_FILE_NAME		/* can override from jconfig.h or Makefile */ 
#define TEMP_FILE_NAME  "%sJPG%03d.TMP" 
#endif 
 
#ifndef NO_ERRNO_H 
#include <errno.h>		/* to define ENOENT */ 
#endif 
 
/* ANSI C specifies that errno is a macro, but on older systems it's more 
 * likely to be a plain int variable.  And not all versions of errno.h 
 * bother to declare it, so we have to in order to be most portable.  Thus: 
 */ 
#ifndef errno 
extern int errno; 
#endif 
 
 
LOCAL(void) 
select_file_name (char * fname) 
{ 
  FILE * tfile; 
 
  /* Keep generating file names till we find one that's not in use */ 
  for (;;) { 
    next_file_num++;		/* advance counter */ 
    sprintf(fname, TEMP_FILE_NAME, TEMP_DIRECTORY, next_file_num); 
    if ((tfile = fopen(fname, READ_BINARY)) == NULL) { 
      /* fopen could have failed for a reason other than the file not 
       * being there; for example, file there but unreadable. 
       * If <errno.h> isn't available, then we cannot test the cause. 
       */ 
#ifdef ENOENT 
      if (errno != ENOENT) 
	continue; 
#endif 
      break; 
    } 
    fclose(tfile);		/* oops, it's there; close tfile & try again */ 
  } 
} 
 
#else /* ! NO_MKTEMP */ 
 
/* Note that mktemp() requires the initial filename to end in six X's */ 
#ifndef TEMP_FILE_NAME		/* can override from jconfig.h or Makefile */ 
#define TEMP_FILE_NAME  "%sJPG%dXXXXXX" 
#endif 
 
LOCAL(void) 
select_file_name (char * fname) 
{ 
  next_file_num++;		/* advance counter */ 
  sprintf(fname, TEMP_FILE_NAME, TEMP_DIRECTORY, next_file_num); 
  mktemp(fname);		/* make sure file name is unique */ 
  /* mktemp replaces the trailing XXXXXX with a unique string of characters */ 
} 
 
#endif /* NO_MKTEMP */ 
 
 
/* 
 * 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);	/* close the file */ 
  unlink(info->temp_name);	/* delete the file */ 
/* If your system doesn't have unlink(), use remove() instead. 
 * remove() is the ANSI-standard name for this function, but if 
 * your system was ANSI you'd be using jmemansi.c, right? 
 */ 
  TRACEMSS(cinfo, 1, JTRC_TFILE_CLOSE, info->temp_name); 
} 
 
 
/* 
 * Initial opening of a backing-store object. 
 */ 
 
GLOBAL(void) 
jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info, 
			 long total_bytes_needed) 
{ 
  select_file_name(info->temp_name); 
  if ((info->temp_file = fopen(info->temp_name, RW_BINARY)) == NULL) 
    ERREXITS(cinfo, JERR_TFILE_CREATE, info->temp_name); 
  info->read_backing_store = read_backing_store; 
  info->write_backing_store = write_backing_store; 
  info->close_backing_store = close_backing_store; 
  TRACEMSS(cinfo, 1, JTRC_TFILE_OPEN, info->temp_name); 
} 
 
 
/* 
 * These routines take care of any system-dependent initialization and 
 * cleanup required. 
 */ 
 
GLOBAL(long) 
jpeg_mem_init (j_common_ptr cinfo) 
{ 
  next_file_num = 0;		/* initialize temp file name generator */ 
  return DEFAULT_MAX_MEM;	/* default for max_memory_to_use */ 
} 
 
GLOBAL(void) 
jpeg_mem_term (j_common_ptr cinfo) 
{ 
  /* no work */ 
}