compiler/libjpeg/main/jmemansi.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jmemansi.c
   7  *
   8  * Copyright (C) 1992-1996, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file provides a simple generic implementation of the system-
  13  * dependent portion of the JPEG memory manager.  This implementation
  14  * assumes that you have the ANSI-standard library routine tmpfile().
  15  * Also, the problem of determining the amount of memory available
  16  * is shoved onto the user.
  17  */
  18
  19 #define JPEG_INTERNALS
  20 #include "jinclude.h"
  21 #include "jpeglib.h"
  22 #include "jmemsys.h"            /* import the system-dependent declarations */
  23
  24 #ifndef HAVE_STDLIB_H           /* <stdlib.h> should declare malloc(),free() */
  25 extern void * malloc JPP((size_t size));
  26 extern void free JPP((void *ptr));
  27 #endif
  28
  29 #ifndef SEEK_SET                /* pre-ANSI systems may not define this; */
  30 #define SEEK_SET  0             /* if not, assume 0 is correct */
  31 #endif
  32
  33
  34 /*
  35  * Memory allocation and freeing are controlled by the regular library
  36  * routines malloc() and free().
  37  */
  38
  39 JGLOBAL(void *)
  40 jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)
  41 {
  42   return (void *) malloc(sizeofobject);
  43 }
  44
  45 JGLOBAL(void)
  46 jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)
  47 {
  48   free(object);
  49 }
  50
  51
  52 /*
  53  * "Large" objects are treated the same as "small" ones.
  54  * NB: although we include FAR keywords in the routine declarations,
  55  * this file won't actually work in 80x86 small/medium model; at least,
  56  * you probably won't be able to process useful-size images in only 64KB.
  57  */
  58
  59 JGLOBAL(void FAR *)
  60 jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)
  61 {
  62   return (void FAR *) malloc(sizeofobject);
  63 }
  64
  65 JGLOBAL(void)
  66 jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)
  67 {
  68   free(object);
  69 }
  70
  71
  72 /*
  73  * This routine computes the total memory space available for allocation.
  74  * It's impossible to do this in a portable way; our current solution is
  75  * to make the user tell us (with a default value set at compile time).
  76  * If you can actually get the available space, it's a good idea to subtract
  77  * a slop factor of 5% or so.
  78  */
  79
  80 #ifndef DEFAULT_MAX_MEM         /* so can override from makefile */
  81 #define DEFAULT_MAX_MEM         1000000L /* default: one megabyte */
  82 #endif
  83
  84 JGLOBAL(long)
  85 jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,
  86                     long max_bytes_needed, long already_allocated)
  87 {
  88   return cinfo->mem->max_memory_to_use - already_allocated;
  89 }
  90
  91
  92 /*
  93  * Backing store (temporary file) management.
  94  * Backing store objects are only used when the value returned by
  95  * jpeg_mem_available is less than the total space needed.  You can dispense
  96  * with these routines if you have plenty of virtual memory; see jmemnobs.c.
  97  */
  98
  99
 100 METHODDEF(void)
 101 read_backing_store (j_common_ptr cinfo, backing_store_ptr info,
 102                     void FAR * buffer_address,
 103                     long file_offset, long byte_count)
 104 {
 105   if (fseek(info->temp_file, file_offset, SEEK_SET))
 106     ERREXIT(cinfo, JERR_TFILE_SEEK);
 107   if (JFREAD(info->temp_file, buffer_address, byte_count)
 108       != (size_t) byte_count)
 109     ERREXIT(cinfo, JERR_TFILE_READ);
 110 }
 111
 112
 113 METHODDEF(void)
 114 write_backing_store (j_common_ptr cinfo, backing_store_ptr info,
 115                      void FAR * buffer_address,
 116                      long file_offset, long byte_count)
 117 {
 118   if (fseek(info->temp_file, file_offset, SEEK_SET))
 119     ERREXIT(cinfo, JERR_TFILE_SEEK);
 120   if (JFWRITE(info->temp_file, buffer_address, byte_count)
 121       != (size_t) byte_count)
 122     ERREXIT(cinfo, JERR_TFILE_WRITE);
 123 }
 124
 125
 126 METHODDEF(void)
 127 close_backing_store (j_common_ptr cinfo, backing_store_ptr info)
 128 {
 129   fclose(info->temp_file);
 130   /* Since this implementation uses tmpfile() to create the file,
 131    * no explicit file deletion is needed.
 132    */
 133 }
 134
 135
 136 /*
 137  * Initial opening of a backing-store object.
 138  *
 139  * This version uses tmpfile(), which constructs a suitable file name
 140  * behind the scenes.  We don't have to use info->temp_name[] at all;
 141  * indeed, we can't even find out the actual name of the temp file.
 142  */
 143
 144 JGLOBAL(void)
 145 jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,
 146                          long total_bytes_needed)
 147 {
 148   if ((info->temp_file = tmpfile()) == NULL)
 149     ERREXITS(cinfo, JERR_TFILE_CREATE, "");
 150   info->read_backing_store = read_backing_store;
 151   info->write_backing_store = write_backing_store;
 152   info->close_backing_store = close_backing_store;
 153 }
 154
 155
 156 /*
 157  * These routines take care of any system-dependent initialization and
 158  * cleanup required.
 159  */
 160
 161 JGLOBAL(long)
 162 jpeg_mem_init (j_common_ptr cinfo)
 163 {
 164   return DEFAULT_MAX_MEM;       /* default for max_memory_to_use */
 165 }
 166
 167 JGLOBAL(void)
 168 jpeg_mem_term (j_common_ptr cinfo)
 169 {
 170   /* no work */
 171 }