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