jmemsys.h (8230B)
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 47 EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject)); 48 EXTERN(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 60 EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo, 61 size_t sizeofobject)); 62 EXTERN(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 */ 102 103 EXTERN(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 */ 120 121 typedef unsigned short XMSH; /* type of extended-memory handles */ 122 typedef unsigned short EMSH; /* type of expanded-memory handles */ 123 124 typedef 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 */ 135 136 137 typedef struct backing_store_struct * backing_store_ptr; 138 139 typedef 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 */ 179 180 EXTERN(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 */ 196 197 EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo)); 198 EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo));