File: jmemsys.h

package info (click to toggle)
libjpeg-turbo 1:1.5.1-2
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 9,068 kB
  • ctags: 6,369
  • sloc: ansic: 43,407; asm: 25,683; sh: 5,436; java: 3,123; makefile: 797; xml: 24
file content (178 lines) | stat: -rw-r--r-- 7,802 bytes parent folder | download | duplicates (12)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
/*
 * jmemsys.h
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1992-1997, Thomas G. Lane.
 * It was modified by The libjpeg-turbo Project to include only code and
 * information relevant to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This include file defines the interface between the system-independent
 * and system-dependent portions of the JPEG memory manager.  No other
 * modules need include it.  (The system-independent portion is jmemmgr.c;
 * there are several different versions of the system-dependent portion.)
 *
 * This file works as-is for the system-dependent memory managers supplied
 * in the IJG distribution.  You may need to modify it if you write a
 * custom memory manager.  If system-dependent changes are needed in
 * this file, the best method is to #ifdef them based on a configuration
 * symbol supplied in jconfig.h.
 */


/*
 * These two functions are used to allocate and release small chunks of
 * memory.  (Typically the total amount requested through jpeg_get_small is
 * no more than 20K or so; this will be requested in chunks of a few K each.)
 * Behavior should be the same as for the standard library functions malloc
 * and free; in particular, jpeg_get_small must return NULL on failure.
 * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
 * size of the object being freed, just in case it's needed.
 */

EXTERN(void *) jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject);
EXTERN(void) jpeg_free_small (j_common_ptr cinfo, void *object,
                              size_t sizeofobject);

/*
 * These two functions are used to allocate and release large chunks of
 * memory (up to the total free space designated by jpeg_mem_available).
 * These are identical to the jpeg_get/free_small routines; but we keep them
 * separate anyway, in case a different allocation strategy is desirable for
 * large chunks.
 */

EXTERN(void *) jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject);
EXTERN(void) jpeg_free_large (j_common_ptr cinfo, void *object,
                              size_t sizeofobject);

/*
 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
 * matter, but that case should never come into play).  This macro was needed
 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
 * On machines with flat address spaces, any large constant may be used.
 *
 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
 * size_t and will be a multiple of sizeof(align_type).
 */

#ifndef MAX_ALLOC_CHUNK         /* may be overridden in jconfig.h */
#define MAX_ALLOC_CHUNK  1000000000L
#endif

/*
 * This routine computes the total space still available for allocation by
 * jpeg_get_large.  If more space than this is needed, backing store will be
 * used.  NOTE: any memory already allocated must not be counted.
 *
 * There is a minimum space requirement, corresponding to the minimum
 * feasible buffer sizes; jmemmgr.c will request that much space even if
 * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
 * all working storage in memory, is also passed in case it is useful.
 * Finally, the total space already allocated is passed.  If no better
 * method is available, cinfo->mem->max_memory_to_use - already_allocated
 * is often a suitable calculation.
 *
 * It is OK for jpeg_mem_available to underestimate the space available
 * (that'll just lead to more backing-store access than is really necessary).
 * However, an overestimate will lead to failure.  Hence it's wise to subtract
 * a slop factor from the true available space.  5% should be enough.
 *
 * On machines with lots of virtual memory, any large constant may be returned.
 * Conversely, zero may be returned to always use the minimum amount of memory.
 */

EXTERN(size_t) jpeg_mem_available (j_common_ptr cinfo, size_t min_bytes_needed,
                                   size_t max_bytes_needed,
                                   size_t already_allocated);


/*
 * This structure holds whatever state is needed to access a single
 * backing-store object.  The read/write/close method pointers are called
 * by jmemmgr.c to manipulate the backing-store object; all other fields
 * are private to the system-dependent backing store routines.
 */

#define TEMP_NAME_LENGTH   64   /* max length of a temporary file's name */


#ifdef USE_MSDOS_MEMMGR         /* DOS-specific junk */

typedef unsigned short XMSH;    /* type of extended-memory handles */
typedef unsigned short EMSH;    /* type of expanded-memory handles */

typedef union {
  short file_handle;            /* DOS file handle if it's a temp file */
  XMSH xms_handle;              /* handle if it's a chunk of XMS */
  EMSH ems_handle;              /* handle if it's a chunk of EMS */
} handle_union;

#endif /* USE_MSDOS_MEMMGR */

#ifdef USE_MAC_MEMMGR           /* Mac-specific junk */
#include <Files.h>
#endif /* USE_MAC_MEMMGR */


typedef struct backing_store_struct *backing_store_ptr;

typedef struct backing_store_struct {
  /* Methods for reading/writing/closing this backing-store object */
  void (*read_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
                              void *buffer_address, long file_offset,
                              long byte_count);
  void (*write_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
                               void *buffer_address, long file_offset,
                               long byte_count);
  void (*close_backing_store) (j_common_ptr cinfo, backing_store_ptr info);

  /* Private fields for system-dependent backing-store management */
#ifdef USE_MSDOS_MEMMGR
  /* For the MS-DOS manager (jmemdos.c), we need: */
  handle_union handle;          /* reference to backing-store storage object */
  char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
#else
#ifdef USE_MAC_MEMMGR
  /* For the Mac manager (jmemmac.c), we need: */
  short temp_file;              /* file reference number to temp file */
  FSSpec tempSpec;              /* the FSSpec for the temp file */
  char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
#else
  /* For a typical implementation with temp files, we need: */
  FILE *temp_file;              /* stdio reference to temp file */
  char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
#endif
#endif
} backing_store_info;


/*
 * Initial opening of a backing-store object.  This must fill in the
 * read/write/close pointers in the object.  The read/write routines
 * may take an error exit if the specified maximum file size is exceeded.
 * (If jpeg_mem_available always returns a large value, this routine can
 * just take an error exit.)
 */

EXTERN(void) jpeg_open_backing_store (j_common_ptr cinfo,
                                      backing_store_ptr info,
                                      long total_bytes_needed);


/*
 * These routines take care of any system-dependent initialization and
 * cleanup required.  jpeg_mem_init will be called before anything is
 * allocated (and, therefore, nothing in cinfo is of use except the error
 * manager pointer).  It should return a suitable default value for
 * max_memory_to_use; this may subsequently be overridden by the surrounding
 * application.  (Note that max_memory_to_use is only important if
 * jpeg_mem_available chooses to consult it ... no one else will.)
 * jpeg_mem_term may assume that all requested memory has been freed and that
 * all opened backing-store objects have been closed.
 */

EXTERN(long) jpeg_mem_init (j_common_ptr cinfo);
EXTERN(void) jpeg_mem_term (j_common_ptr cinfo);