4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1992-1997, Thomas G. Lane.
6 * It was modified by The libjpeg-turbo Project to include only code and
7 * information relevant to libjpeg-turbo.
8 * For conditions of distribution and use, see the accompanying README.ijg
11 * This include file defines the interface between the system-independent
12 * and system-dependent portions of the JPEG memory manager. No other
13 * modules need include it. (The system-independent portion is jmemmgr.c;
14 * there are several different versions of the system-dependent portion.)
16 * This file works as-is for the system-dependent memory managers supplied
17 * in the IJG distribution. You may need to modify it if you write a
18 * custom memory manager. If system-dependent changes are needed in
19 * this file, the best method is to #ifdef them based on a configuration
20 * symbol supplied in jconfig.h.
25 * These two functions are used to allocate and release small chunks of
26 * memory. (Typically the total amount requested through jpeg_get_small is
27 * no more than 20K or so; this will be requested in chunks of a few K each.)
28 * Behavior should be the same as for the standard library functions malloc
29 * and free; in particular, jpeg_get_small must return NULL on failure.
30 * On most systems, these ARE malloc and free. jpeg_free_small is passed the
31 * size of the object being freed, just in case it's needed.
34 EXTERN(void *) jpeg_get_small(j_common_ptr cinfo, size_t sizeofobject);
35 EXTERN(void) jpeg_free_small(j_common_ptr cinfo, void *object,
39 * These two functions are used to allocate and release large chunks of
40 * memory (up to the total free space designated by jpeg_mem_available).
41 * These are identical to the jpeg_get/free_small routines; but we keep them
42 * separate anyway, in case a different allocation strategy is desirable for
46 EXTERN(void *) jpeg_get_large(j_common_ptr cinfo, size_t sizeofobject);
47 EXTERN(void) jpeg_free_large(j_common_ptr cinfo, void *object,
51 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
52 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
53 * matter, but that case should never come into play). This macro was needed
54 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
55 * On machines with flat address spaces, any large constant may be used.
57 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
58 * size_t and will be a multiple of sizeof(align_type).
61 #ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */
62 #define MAX_ALLOC_CHUNK 1000000000L
66 * This routine computes the total space still available for allocation by
67 * jpeg_get_large. If more space than this is needed, backing store will be
68 * used. NOTE: any memory already allocated must not be counted.
70 * There is a minimum space requirement, corresponding to the minimum
71 * feasible buffer sizes; jmemmgr.c will request that much space even if
72 * jpeg_mem_available returns zero. The maximum space needed, enough to hold
73 * all working storage in memory, is also passed in case it is useful.
74 * Finally, the total space already allocated is passed. If no better
75 * method is available, cinfo->mem->max_memory_to_use - already_allocated
76 * is often a suitable calculation.
78 * It is OK for jpeg_mem_available to underestimate the space available
79 * (that'll just lead to more backing-store access than is really necessary).
80 * However, an overestimate will lead to failure. Hence it's wise to subtract
81 * a slop factor from the true available space. 5% should be enough.
83 * On machines with lots of virtual memory, any large constant may be returned.
84 * Conversely, zero may be returned to always use the minimum amount of memory.
87 EXTERN(size_t) jpeg_mem_available(j_common_ptr cinfo, size_t min_bytes_needed,
88 size_t max_bytes_needed,
89 size_t already_allocated);
93 * This structure holds whatever state is needed to access a single
94 * backing-store object. The read/write/close method pointers are called
95 * by jmemmgr.c to manipulate the backing-store object; all other fields
96 * are private to the system-dependent backing store routines.
99 #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */
102 #ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */
104 typedef unsigned short XMSH; /* type of extended-memory handles */
105 typedef unsigned short EMSH; /* type of expanded-memory handles */
108 short file_handle; /* DOS file handle if it's a temp file */
109 XMSH xms_handle; /* handle if it's a chunk of XMS */
110 EMSH ems_handle; /* handle if it's a chunk of EMS */
113 #endif /* USE_MSDOS_MEMMGR */
115 #ifdef USE_MAC_MEMMGR /* Mac-specific junk */
117 #endif /* USE_MAC_MEMMGR */
120 typedef struct backing_store_struct *backing_store_ptr;
122 typedef struct backing_store_struct {
123 /* Methods for reading/writing/closing this backing-store object */
124 void (*read_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
125 void *buffer_address, long file_offset,
127 void (*write_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
128 void *buffer_address, long file_offset,
130 void (*close_backing_store) (j_common_ptr cinfo, backing_store_ptr info);
132 /* Private fields for system-dependent backing-store management */
133 #ifdef USE_MSDOS_MEMMGR
134 /* For the MS-DOS manager (jmemdos.c), we need: */
135 handle_union handle; /* reference to backing-store storage object */
136 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
138 #ifdef USE_MAC_MEMMGR
139 /* For the Mac manager (jmemmac.c), we need: */
140 short temp_file; /* file reference number to temp file */
141 FSSpec tempSpec; /* the FSSpec for the temp file */
142 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
144 /* For a typical implementation with temp files, we need: */
145 FILE *temp_file; /* stdio reference to temp file */
146 char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
149 } backing_store_info;
153 * Initial opening of a backing-store object. This must fill in the
154 * read/write/close pointers in the object. The read/write routines
155 * may take an error exit if the specified maximum file size is exceeded.
156 * (If jpeg_mem_available always returns a large value, this routine can
157 * just take an error exit.)
160 EXTERN(void) jpeg_open_backing_store(j_common_ptr cinfo,
161 backing_store_ptr info,
162 long total_bytes_needed);
166 * These routines take care of any system-dependent initialization and
167 * cleanup required. jpeg_mem_init will be called before anything is
168 * allocated (and, therefore, nothing in cinfo is of use except the error
169 * manager pointer). It should return a suitable default value for
170 * max_memory_to_use; this may subsequently be overridden by the surrounding
171 * application. (Note that max_memory_to_use is only important if
172 * jpeg_mem_available chooses to consult it ... no one else will.)
173 * jpeg_mem_term may assume that all requested memory has been freed and that
174 * all opened backing-store objects have been closed.
177 EXTERN(long) jpeg_mem_init(j_common_ptr cinfo);
178 EXTERN(void) jpeg_mem_term(j_common_ptr cinfo);