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() */
21extern void * malloc JPP((size_t size));
22extern 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
35GLOBAL(void *)
36jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)
37{
38 return (void *) malloc(sizeofobject);
39}
40
41GLOBAL(void)
42jpeg_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
55GLOBAL(void FAR *)
56jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)
57{
58 return (void FAR *) malloc(sizeofobject);
59}
60
61GLOBAL(void)
62jpeg_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
80GLOBAL(long)
81jpeg_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
96METHODDEF(void)
97read_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
109METHODDEF(void)
110write_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
122METHODDEF(void)
123close_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
140GLOBAL(void)
141jpeg_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
157GLOBAL(long)
158jpeg_mem_init (j_common_ptr cinfo)
159{
160 return DEFAULT_MAX_MEM; /* default for max_memory_to_use */
161}
162
163GLOBAL(void)
164jpeg_mem_term (j_common_ptr cinfo)
165{
166 /* no work */
167}
168