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 }