source: golgotha/src/i4/loaders/jpg/jmemsys.h @ 80

Last change on this file since 80 was 80, checked in by Sam Hocevar, 12 years ago
  • Adding the Golgotha source code. Not sure what's going to be interesting in there, but since it's all public domain, there's certainly stuff to pick up.
  • Property svn:keywords set to Id
File size: 7.8 KB
Line 
1/*
2 * jmemsys.h
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 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 */
19
20
21/* Short forms of external names for systems with brain-damaged linkers. */
22
23#ifdef NEED_SHORT_EXTERNAL_NAMES
24#define jpeg_get_small          jGetSmall
25#define jpeg_free_small         jFreeSmall
26#define jpeg_get_large          jGetLarge
27#define jpeg_free_large         jFreeLarge
28#define jpeg_mem_available      jMemAvail
29#define jpeg_open_backing_store jOpenBackStore
30#define jpeg_mem_init           jMemInit
31#define jpeg_mem_term           jMemTerm
32#endif /* NEED_SHORT_EXTERNAL_NAMES */
33
34
35/*
36 * These two functions are used to allocate and release small chunks of
37 * memory.  (Typically the total amount requested through jpeg_get_small is
38 * no more than 20K or so; this will be requested in chunks of a few K each.)
39 * Behavior should be the same as for the standard library functions malloc
40 * and free; in particular, jpeg_get_small must return NULL on failure.
41 * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
42 * size of the object being freed, just in case it's needed.
43 * On an 80x86 machine using small-data memory model, these manage near heap.
44 */
45
46EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
47EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object,
48                                  size_t sizeofobject));
49
50/*
51 * These two functions are used to allocate and release large chunks of
52 * memory (up to the total free space designated by jpeg_mem_available).
53 * The interface is the same as above, except that on an 80x86 machine,
54 * far pointers are used.  On most other machines these are identical to
55 * the jpeg_get/free_small routines; but we keep them separate anyway,
56 * in case a different allocation strategy is desirable for large chunks.
57 */
58
59EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
60                                       size_t sizeofobject));
61EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
62                                  size_t sizeofobject));
63
64/*
65 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
66 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
67 * matter, but that case should never come into play).  This macro is needed
68 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
69 * On those machines, we expect that jconfig.h will provide a proper value.
70 * On machines with 32-bit flat address spaces, any large constant may be used.
71 *
72 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
73 * size_t and will be a multiple of sizeof(align_type).
74 */
75
76#ifndef MAX_ALLOC_CHUNK         /* may be overridden in jconfig.h */
77#define MAX_ALLOC_CHUNK  1000000000L
78#endif
79
80/*
81 * This routine computes the total space still available for allocation by
82 * jpeg_get_large.  If more space than this is needed, backing store will be
83 * used.  NOTE: any memory already allocated must not be counted.
84 *
85 * There is a minimum space requirement, corresponding to the minimum
86 * feasible buffer sizes; jmemmgr.c will request that much space even if
87 * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
88 * all working storage in memory, is also passed in case it is useful.
89 * Finally, the total space already allocated is passed.  If no better
90 * method is available, cinfo->mem->max_memory_to_use - already_allocated
91 * is often a suitable calculation.
92 *
93 * It is OK for jpeg_mem_available to underestimate the space available
94 * (that'll just lead to more backing-store access than is really necessary).
95 * However, an overestimate will lead to failure.  Hence it's wise to subtract
96 * a slop factor from the true available space.  5% should be enough.
97 *
98 * On machines with lots of virtual memory, any large constant may be returned.
99 * Conversely, zero may be returned to always use the minimum amount of memory.
100 */
101
102EXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo,
103                                     long min_bytes_needed,
104                                     long max_bytes_needed,
105                                     long already_allocated));
106
107
108/*
109 * This structure holds whatever state is needed to access a single
110 * backing-store object.  The read/write/close method pointers are called
111 * by jmemmgr.c to manipulate the backing-store object; all other fields
112 * are private to the system-dependent backing store routines.
113 */
114
115#define TEMP_NAME_LENGTH   64   /* max length of a temporary file's name */
116
117#ifdef USE_MSDOS_MEMMGR         /* DOS-specific junk */
118
119typedef unsigned short XMSH;    /* type of extended-memory handles */
120typedef unsigned short EMSH;    /* type of expanded-memory handles */
121
122typedef union {
123  short file_handle;            /* DOS file handle if it's a temp file */
124  XMSH xms_handle;              /* handle if it's a chunk of XMS */
125  EMSH ems_handle;              /* handle if it's a chunk of EMS */
126} handle_union;
127
128#endif /* USE_MSDOS_MEMMGR */
129
130typedef struct backing_store_struct * backing_store_ptr;
131
132typedef struct backing_store_struct {
133  /* Methods for reading/writing/closing this backing-store object */
134  JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
135                                     backing_store_ptr info,
136                                     void FAR * buffer_address,
137                                     long file_offset, long byte_count));
138  JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
139                                      backing_store_ptr info,
140                                      void FAR * buffer_address,
141                                      long file_offset, long byte_count));
142  JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
143                                      backing_store_ptr info));
144
145  /* Private fields for system-dependent backing-store management */
146#ifdef USE_MSDOS_MEMMGR
147  /* For the MS-DOS manager (jmemdos.c), we need: */
148  handle_union handle;          /* reference to backing-store storage object */
149  char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
150#else
151  /* For a typical implementation with temp files, we need: */
152  FILE * temp_file;             /* stdio reference to temp file */
153  char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
154#endif
155} backing_store_info;
156
157/*
158 * Initial opening of a backing-store object.  This must fill in the
159 * read/write/close pointers in the object.  The read/write routines
160 * may take an error exit if the specified maximum file size is exceeded.
161 * (If jpeg_mem_available always returns a large value, this routine can
162 * just take an error exit.)
163 */
164
165EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
166                                          backing_store_ptr info,
167                                          long total_bytes_needed));
168
169
170/*
171 * These routines take care of any system-dependent initialization and
172 * cleanup required.  jpeg_mem_init will be called before anything is
173 * allocated (and, therefore, nothing in cinfo is of use except the error
174 * manager pointer).  It should return a suitable default value for
175 * max_memory_to_use; this may subsequently be overridden by the surrounding
176 * application.  (Note that max_memory_to_use is only important if
177 * jpeg_mem_available chooses to consult it ... no one else will.)
178 * jpeg_mem_term may assume that all requested memory has been freed and that
179 * all opened backing-store objects have been closed.
180 */
181
182EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
183EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));
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