1/*
2 * jmemsys.h
3 *
4 * Copyright (C) 1992-1997, 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 include file defines the interface between the system-independent
9 * and system-dependent portions of the JPEG memory manager. No other
10 * modules need include it. (The system-independent portion is jmemmgr.c;
11 * there are several different versions of the system-dependent portion.)
12 *
13 * This file works as-is for the system-dependent memory managers supplied
14 * in the IJG distribution. You may need to modify it if you write a
15 * custom memory manager. If system-dependent changes are needed in
16 * this file, the best method is to #ifdef them based on a configuration
17 * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR
18 * and USE_MAC_MEMMGR.
19 */
20
21
22/* Short forms of external names for systems with brain-damaged linkers. */
23
24#ifdef NEED_SHORT_EXTERNAL_NAMES
25#define jpeg_get_small jGetSmall
26#define jpeg_free_small jFreeSmall
27#define jpeg_get_large jGetLarge
28#define jpeg_free_large jFreeLarge
29#define jpeg_mem_available jMemAvail
30#define jpeg_open_backing_store jOpenBackStore
31#define jpeg_mem_init jMemInit
32#define jpeg_mem_term jMemTerm
33#endif /* NEED_SHORT_EXTERNAL_NAMES */
34
35
36/*
37 * These two functions are used to allocate and release small chunks of
38 * memory. (Typically the total amount requested through jpeg_get_small is
39 * no more than 20K or so; this will be requested in chunks of a few K each.)
40 * Behavior should be the same as for the standard library functions malloc
41 * and free; in particular, jpeg_get_small must return NULL on failure.
42 * On most systems, these ARE malloc and free. jpeg_free_small is passed the
43 * size of the object being freed, just in case it's needed.
44 * On an 80x86 machine using small-data memory model, these manage near heap.
45 */
46
47EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
48EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object,
49 size_t sizeofobject));
50
51/*
52 * These two functions are used to allocate and release large chunks of
53 * memory (up to the total free space designated by jpeg_mem_available).
54 * The interface is the same as above, except that on an 80x86 machine,
55 * far pointers are used. On most other machines these are identical to
56 * the jpeg_get/free_small routines; but we keep them separate anyway,
57 * in case a different allocation strategy is desirable for large chunks.
58 */
59
60EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
61 size_t sizeofobject));
62EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
63 size_t sizeofobject));
64
65/*
66 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
67 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
68 * matter, but that case should never come into play). This macro is needed
69 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
70 * On those machines, we expect that jconfig.h will provide a proper value.
71 * On machines with 32-bit flat address spaces, any large constant may be used.
72 *
73 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
74 * size_t and will be a multiple of sizeof(align_type).
75 */
76
77#ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */
78#define MAX_ALLOC_CHUNK 1000000000L
79#endif
80
81/*
82 * This routine computes the total space still available for allocation by
83 * jpeg_get_large. If more space than this is needed, backing store will be
84 * used. NOTE: any memory already allocated must not be counted.
85 *
86 * There is a minimum space requirement, corresponding to the minimum
87 * feasible buffer sizes; jmemmgr.c will request that much space even if
88 * jpeg_mem_available returns zero. The maximum space needed, enough to hold
89 * all working storage in memory, is also passed in case it is useful.
90 * Finally, the total space already allocated is passed. If no better
91 * method is available, cinfo->mem->max_memory_to_use - already_allocated
92 * is often a suitable calculation.
93 *
94 * It is OK for jpeg_mem_available to underestimate the space available
95 * (that'll just lead to more backing-store access than is really necessary).
96 * However, an overestimate will lead to failure. Hence it's wise to subtract
97 * a slop factor from the true available space. 5% should be enough.
98 *
99 * On machines with lots of virtual memory, any large constant may be returned.
100 * Conversely, zero may be returned to always use the minimum amount of memory.
101 */
102
103EXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo,
104 long min_bytes_needed,
105 long max_bytes_needed,
106 long already_allocated));
107
108
109/*
110 * This structure holds whatever state is needed to access a single
111 * backing-store object. The read/write/close method pointers are called
112 * by jmemmgr.c to manipulate the backing-store object; all other fields
113 * are private to the system-dependent backing store routines.
114 */
115
116#define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */
117
118
119#ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */
120
121typedef unsigned short XMSH; /* type of extended-memory handles */
122typedef unsigned short EMSH; /* type of expanded-memory handles */
123
124typedef union {
125 short file_handle; /* DOS file handle if it's a temp file */
126 XMSH xms_handle; /* handle if it's a chunk of XMS */
127 EMSH ems_handle; /* handle if it's a chunk of EMS */
128} handle_union;
129
130#endif /* USE_MSDOS_MEMMGR */
131
132#ifdef USE_MAC_MEMMGR /* Mac-specific junk */
133#include <Files.h>
134#endif /* USE_MAC_MEMMGR */
135
136
137typedef struct backing_store_struct * backing_store_ptr;
138
139typedef struct backing_store_struct {
140 /* Methods for reading/writing/closing this backing-store object */
141 JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
142 backing_store_ptr info,
143 void FAR * buffer_address,
144 long file_offset, long byte_count));
145 JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
146 backing_store_ptr info,
147 void FAR * buffer_address,
148 long file_offset, long byte_count));
149 JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
150 backing_store_ptr info));
151
152 /* Private fields for system-dependent backing-store management */
153#ifdef USE_MSDOS_MEMMGR
154 /* For the MS-DOS manager (jmemdos.c), we need: */
155 handle_union handle; /* reference to backing-store storage object */
156 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
157#else
158#ifdef USE_MAC_MEMMGR
159 /* For the Mac manager (jmemmac.c), we need: */
160 short temp_file; /* file reference number to temp file */
161 FSSpec tempSpec; /* the FSSpec for the temp file */
162 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
163#else
164 /* For a typical implementation with temp files, we need: */
165 FILE * temp_file; /* stdio reference to temp file */
166 char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
167#endif
168#endif
169} backing_store_info;
170
171
172/*
173 * Initial opening of a backing-store object. This must fill in the
174 * read/write/close pointers in the object. The read/write routines
175 * may take an error exit if the specified maximum file size is exceeded.
176 * (If jpeg_mem_available always returns a large value, this routine can
177 * just take an error exit.)
178 */
179
180EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
181 backing_store_ptr info,
182 long total_bytes_needed));
183
184
185/*
186 * These routines take care of any system-dependent initialization and
187 * cleanup required. jpeg_mem_init will be called before anything is
188 * allocated (and, therefore, nothing in cinfo is of use except the error
189 * manager pointer). It should return a suitable default value for
190 * max_memory_to_use; this may subsequently be overridden by the surrounding
191 * application. (Note that max_memory_to_use is only important if
192 * jpeg_mem_available chooses to consult it ... no one else will.)
193 * jpeg_mem_term may assume that all requested memory has been freed and that
194 * all opened backing-store objects have been closed.
195 */
196
197EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
198EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));
199