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annotate libs/libjpeg/jmemsys.h @ 35:643f4ab609a4

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added readme and license
author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 31 Oct 2015 05:45:35 +0200
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nuclear@2 1 /*
nuclear@2 2 * jmemsys.h
nuclear@2 3 *
nuclear@2 4 * Copyright (C) 1992-1997, Thomas G. Lane.
nuclear@2 5 * This file is part of the Independent JPEG Group's software.
nuclear@2 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@2 7 *
nuclear@2 8 * This include file defines the interface between the system-independent
nuclear@2 9 * and system-dependent portions of the JPEG memory manager. No other
nuclear@2 10 * modules need include it. (The system-independent portion is jmemmgr.c;
nuclear@2 11 * there are several different versions of the system-dependent portion.)
nuclear@2 12 *
nuclear@2 13 * This file works as-is for the system-dependent memory managers supplied
nuclear@2 14 * in the IJG distribution. You may need to modify it if you write a
nuclear@2 15 * custom memory manager. If system-dependent changes are needed in
nuclear@2 16 * this file, the best method is to #ifdef them based on a configuration
nuclear@2 17 * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR
nuclear@2 18 * and USE_MAC_MEMMGR.
nuclear@2 19 */
nuclear@2 20
nuclear@2 21
nuclear@2 22 /* Short forms of external names for systems with brain-damaged linkers. */
nuclear@2 23
nuclear@2 24 #ifdef NEED_SHORT_EXTERNAL_NAMES
nuclear@2 25 #define jpeg_get_small jGetSmall
nuclear@2 26 #define jpeg_free_small jFreeSmall
nuclear@2 27 #define jpeg_get_large jGetLarge
nuclear@2 28 #define jpeg_free_large jFreeLarge
nuclear@2 29 #define jpeg_mem_available jMemAvail
nuclear@2 30 #define jpeg_open_backing_store jOpenBackStore
nuclear@2 31 #define jpeg_mem_init jMemInit
nuclear@2 32 #define jpeg_mem_term jMemTerm
nuclear@2 33 #endif /* NEED_SHORT_EXTERNAL_NAMES */
nuclear@2 34
nuclear@2 35
nuclear@2 36 /*
nuclear@2 37 * These two functions are used to allocate and release small chunks of
nuclear@2 38 * memory. (Typically the total amount requested through jpeg_get_small is
nuclear@2 39 * no more than 20K or so; this will be requested in chunks of a few K each.)
nuclear@2 40 * Behavior should be the same as for the standard library functions malloc
nuclear@2 41 * and free; in particular, jpeg_get_small must return NULL on failure.
nuclear@2 42 * On most systems, these ARE malloc and free. jpeg_free_small is passed the
nuclear@2 43 * size of the object being freed, just in case it's needed.
nuclear@2 44 * On an 80x86 machine using small-data memory model, these manage near heap.
nuclear@2 45 */
nuclear@2 46
nuclear@2 47 EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject));
nuclear@2 48 EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object,
nuclear@2 49 size_t sizeofobject));
nuclear@2 50
nuclear@2 51 /*
nuclear@2 52 * These two functions are used to allocate and release large chunks of
nuclear@2 53 * memory (up to the total free space designated by jpeg_mem_available).
nuclear@2 54 * The interface is the same as above, except that on an 80x86 machine,
nuclear@2 55 * far pointers are used. On most other machines these are identical to
nuclear@2 56 * the jpeg_get/free_small routines; but we keep them separate anyway,
nuclear@2 57 * in case a different allocation strategy is desirable for large chunks.
nuclear@2 58 */
nuclear@2 59
nuclear@2 60 EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo,
nuclear@2 61 size_t sizeofobject));
nuclear@2 62 EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object,
nuclear@2 63 size_t sizeofobject));
nuclear@2 64
nuclear@2 65 /*
nuclear@2 66 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
nuclear@2 67 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
nuclear@2 68 * matter, but that case should never come into play). This macro is needed
nuclear@2 69 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
nuclear@2 70 * On those machines, we expect that jconfig.h will provide a proper value.
nuclear@2 71 * On machines with 32-bit flat address spaces, any large constant may be used.
nuclear@2 72 *
nuclear@2 73 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
nuclear@2 74 * size_t and will be a multiple of sizeof(align_type).
nuclear@2 75 */
nuclear@2 76
nuclear@2 77 #ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */
nuclear@2 78 #define MAX_ALLOC_CHUNK 1000000000L
nuclear@2 79 #endif
nuclear@2 80
nuclear@2 81 /*
nuclear@2 82 * This routine computes the total space still available for allocation by
nuclear@2 83 * jpeg_get_large. If more space than this is needed, backing store will be
nuclear@2 84 * used. NOTE: any memory already allocated must not be counted.
nuclear@2 85 *
nuclear@2 86 * There is a minimum space requirement, corresponding to the minimum
nuclear@2 87 * feasible buffer sizes; jmemmgr.c will request that much space even if
nuclear@2 88 * jpeg_mem_available returns zero. The maximum space needed, enough to hold
nuclear@2 89 * all working storage in memory, is also passed in case it is useful.
nuclear@2 90 * Finally, the total space already allocated is passed. If no better
nuclear@2 91 * method is available, cinfo->mem->max_memory_to_use - already_allocated
nuclear@2 92 * is often a suitable calculation.
nuclear@2 93 *
nuclear@2 94 * It is OK for jpeg_mem_available to underestimate the space available
nuclear@2 95 * (that'll just lead to more backing-store access than is really necessary).
nuclear@2 96 * However, an overestimate will lead to failure. Hence it's wise to subtract
nuclear@2 97 * a slop factor from the true available space. 5% should be enough.
nuclear@2 98 *
nuclear@2 99 * On machines with lots of virtual memory, any large constant may be returned.
nuclear@2 100 * Conversely, zero may be returned to always use the minimum amount of memory.
nuclear@2 101 */
nuclear@2 102
nuclear@2 103 EXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo,
nuclear@2 104 long min_bytes_needed,
nuclear@2 105 long max_bytes_needed,
nuclear@2 106 long already_allocated));
nuclear@2 107
nuclear@2 108
nuclear@2 109 /*
nuclear@2 110 * This structure holds whatever state is needed to access a single
nuclear@2 111 * backing-store object. The read/write/close method pointers are called
nuclear@2 112 * by jmemmgr.c to manipulate the backing-store object; all other fields
nuclear@2 113 * are private to the system-dependent backing store routines.
nuclear@2 114 */
nuclear@2 115
nuclear@2 116 #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */
nuclear@2 117
nuclear@2 118
nuclear@2 119 #ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */
nuclear@2 120
nuclear@2 121 typedef unsigned short XMSH; /* type of extended-memory handles */
nuclear@2 122 typedef unsigned short EMSH; /* type of expanded-memory handles */
nuclear@2 123
nuclear@2 124 typedef union {
nuclear@2 125 short file_handle; /* DOS file handle if it's a temp file */
nuclear@2 126 XMSH xms_handle; /* handle if it's a chunk of XMS */
nuclear@2 127 EMSH ems_handle; /* handle if it's a chunk of EMS */
nuclear@2 128 } handle_union;
nuclear@2 129
nuclear@2 130 #endif /* USE_MSDOS_MEMMGR */
nuclear@2 131
nuclear@2 132 #ifdef USE_MAC_MEMMGR /* Mac-specific junk */
nuclear@2 133 #include <Files.h>
nuclear@2 134 #endif /* USE_MAC_MEMMGR */
nuclear@2 135
nuclear@2 136
nuclear@2 137 typedef struct backing_store_struct * backing_store_ptr;
nuclear@2 138
nuclear@2 139 typedef struct backing_store_struct {
nuclear@2 140 /* Methods for reading/writing/closing this backing-store object */
nuclear@2 141 JMETHOD(void, read_backing_store, (j_common_ptr cinfo,
nuclear@2 142 backing_store_ptr info,
nuclear@2 143 void FAR * buffer_address,
nuclear@2 144 long file_offset, long byte_count));
nuclear@2 145 JMETHOD(void, write_backing_store, (j_common_ptr cinfo,
nuclear@2 146 backing_store_ptr info,
nuclear@2 147 void FAR * buffer_address,
nuclear@2 148 long file_offset, long byte_count));
nuclear@2 149 JMETHOD(void, close_backing_store, (j_common_ptr cinfo,
nuclear@2 150 backing_store_ptr info));
nuclear@2 151
nuclear@2 152 /* Private fields for system-dependent backing-store management */
nuclear@2 153 #ifdef USE_MSDOS_MEMMGR
nuclear@2 154 /* For the MS-DOS manager (jmemdos.c), we need: */
nuclear@2 155 handle_union handle; /* reference to backing-store storage object */
nuclear@2 156 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
nuclear@2 157 #else
nuclear@2 158 #ifdef USE_MAC_MEMMGR
nuclear@2 159 /* For the Mac manager (jmemmac.c), we need: */
nuclear@2 160 short temp_file; /* file reference number to temp file */
nuclear@2 161 FSSpec tempSpec; /* the FSSpec for the temp file */
nuclear@2 162 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
nuclear@2 163 #else
nuclear@2 164 /* For a typical implementation with temp files, we need: */
nuclear@2 165 FILE * temp_file; /* stdio reference to temp file */
nuclear@2 166 char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
nuclear@2 167 #endif
nuclear@2 168 #endif
nuclear@2 169 } backing_store_info;
nuclear@2 170
nuclear@2 171
nuclear@2 172 /*
nuclear@2 173 * Initial opening of a backing-store object. This must fill in the
nuclear@2 174 * read/write/close pointers in the object. The read/write routines
nuclear@2 175 * may take an error exit if the specified maximum file size is exceeded.
nuclear@2 176 * (If jpeg_mem_available always returns a large value, this routine can
nuclear@2 177 * just take an error exit.)
nuclear@2 178 */
nuclear@2 179
nuclear@2 180 EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo,
nuclear@2 181 backing_store_ptr info,
nuclear@2 182 long total_bytes_needed));
nuclear@2 183
nuclear@2 184
nuclear@2 185 /*
nuclear@2 186 * These routines take care of any system-dependent initialization and
nuclear@2 187 * cleanup required. jpeg_mem_init will be called before anything is
nuclear@2 188 * allocated (and, therefore, nothing in cinfo is of use except the error
nuclear@2 189 * manager pointer). It should return a suitable default value for
nuclear@2 190 * max_memory_to_use; this may subsequently be overridden by the surrounding
nuclear@2 191 * application. (Note that max_memory_to_use is only important if
nuclear@2 192 * jpeg_mem_available chooses to consult it ... no one else will.)
nuclear@2 193 * jpeg_mem_term may assume that all requested memory has been freed and that
nuclear@2 194 * all opened backing-store objects have been closed.
nuclear@2 195 */
nuclear@2 196
nuclear@2 197 EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo));
nuclear@2 198 EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));