1/* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5/* 6 * jmemsys.h 7 * 8 * Copyright (C) 1992-1997, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This include file defines the interface between the system-independent 13 * and system-dependent portions of the JPEG memory manager. No other 14 * modules need include it. (The system-independent portion is jmemmgr.c; 15 * there are several different versions of the system-dependent portion.) 16 * 17 * This file works as-is for the system-dependent memory managers supplied 18 * in the IJG distribution. You may need to modify it if you write a 19 * custom memory manager. If system-dependent changes are needed in 20 * this file, the best method is to #ifdef them based on a configuration 21 * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR 22 * and USE_MAC_MEMMGR. 23 */ 24 25 26/* Short forms of external names for systems with brain-damaged linkers. */ 27 28#ifdef NEED_SHORT_EXTERNAL_NAMES 29#define jpeg_get_small jGetSmall 30#define jpeg_free_small jFreeSmall 31#define jpeg_get_large jGetLarge 32#define jpeg_free_large jFreeLarge 33#define jpeg_mem_available jMemAvail 34#define jpeg_open_backing_store jOpenBackStore 35#define jpeg_mem_init jMemInit 36#define jpeg_mem_term jMemTerm 37#endif /* NEED_SHORT_EXTERNAL_NAMES */ 38 39 40/* 41 * These two functions are used to allocate and release small chunks of 42 * memory. (Typically the total amount requested through jpeg_get_small is 43 * no more than 20K or so; this will be requested in chunks of a few K each.) 44 * Behavior should be the same as for the standard library functions malloc 45 * and free; in particular, jpeg_get_small must return NULL on failure. 46 * On most systems, these ARE malloc and free. jpeg_free_small is passed the 47 * size of the object being freed, just in case it's needed. 48 * On an 80x86 machine using small-data memory model, these manage near heap. 49 */ 50 51EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject)); 52EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object, 53 size_t sizeofobject)); 54 55/* 56 * These two functions are used to allocate and release large chunks of 57 * memory (up to the total free space designated by jpeg_mem_available). 58 * The interface is the same as above, except that on an 80x86 machine, 59 * far pointers are used. On most other machines these are identical to 60 * the jpeg_get/free_small routines; but we keep them separate anyway, 61 * in case a different allocation strategy is desirable for large chunks. 62 */ 63 64EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo, 65 size_t sizeofobject)); 66EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object, 67 size_t sizeofobject)); 68 69/* 70 * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may 71 * be requested in a single call to jpeg_get_large (and jpeg_get_small for that 72 * matter, but that case should never come into play). This macro is needed 73 * to model the 64Kb-segment-size limit of far addressing on 80x86 machines. 74 * On those machines, we expect that jconfig.h will provide a proper value. 75 * On machines with 32-bit flat address spaces, any large constant may be used. 76 * 77 * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type 78 * size_t and will be a multiple of sizeof(align_type). 79 */ 80 81#ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */ 82#define MAX_ALLOC_CHUNK 1000000000L 83#endif 84 85/* 86 * This routine computes the total space still available for allocation by 87 * jpeg_get_large. If more space than this is needed, backing store will be 88 * used. NOTE: any memory already allocated must not be counted. 89 * 90 * There is a minimum space requirement, corresponding to the minimum 91 * feasible buffer sizes; jmemmgr.c will request that much space even if 92 * jpeg_mem_available returns zero. The maximum space needed, enough to hold 93 * all working storage in memory, is also passed in case it is useful. 94 * Finally, the total space already allocated is passed. If no better 95 * method is available, cinfo->mem->max_memory_to_use - already_allocated 96 * is often a suitable calculation. 97 * 98 * It is OK for jpeg_mem_available to underestimate the space available 99 * (that'll just lead to more backing-store access than is really necessary). 100 * However, an overestimate will lead to failure. Hence it's wise to subtract 101 * a slop factor from the true available space. 5% should be enough. 102 * 103 * On machines with lots of virtual memory, any large constant may be returned. 104 * Conversely, zero may be returned to always use the minimum amount of memory. 105 */ 106 107EXTERN(size_t) jpeg_mem_available JPP((j_common_ptr cinfo, 108 size_t min_bytes_needed, 109 size_t max_bytes_needed, 110 size_t already_allocated)); 111 112 113/* 114 * This structure holds whatever state is needed to access a single 115 * backing-store object. The read/write/close method pointers are called 116 * by jmemmgr.c to manipulate the backing-store object; all other fields 117 * are private to the system-dependent backing store routines. 118 */ 119 120#define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */ 121 122 123#ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */ 124 125typedef unsigned short XMSH; /* type of extended-memory handles */ 126typedef unsigned short EMSH; /* type of expanded-memory handles */ 127 128typedef union { 129 short file_handle; /* DOS file handle if it's a temp file */ 130 XMSH xms_handle; /* handle if it's a chunk of XMS */ 131 EMSH ems_handle; /* handle if it's a chunk of EMS */ 132} handle_union; 133 134#endif /* USE_MSDOS_MEMMGR */ 135 136#ifdef USE_MAC_MEMMGR /* Mac-specific junk */ 137#include <Files.h> 138#endif /* USE_MAC_MEMMGR */ 139 140 141typedef struct backing_store_struct * backing_store_ptr; 142 143typedef struct backing_store_struct { 144 /* Methods for reading/writing/closing this backing-store object */ 145 JMETHOD(void, read_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, write_backing_store, (j_common_ptr cinfo, 150 backing_store_ptr info, 151 void FAR * buffer_address, 152 long file_offset, long byte_count)); 153 JMETHOD(void, close_backing_store, (j_common_ptr cinfo, 154 backing_store_ptr info)); 155 156 /* Private fields for system-dependent backing-store management */ 157#ifdef USE_MSDOS_MEMMGR 158 /* For the MS-DOS manager (jmemdos.c), we need: */ 159 handle_union handle; /* reference to backing-store storage object */ 160 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */ 161#else 162#ifdef USE_MAC_MEMMGR 163 /* For the Mac manager (jmemmac.c), we need: */ 164 short temp_file; /* file reference number to temp file */ 165 FSSpec tempSpec; /* the FSSpec for the temp file */ 166 char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */ 167#else 168 /* For a typical implementation with temp files, we need: */ 169 FILE * temp_file; /* stdio reference to temp file */ 170 char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */ 171#endif 172#endif 173} backing_store_info; 174 175 176/* 177 * Initial opening of a backing-store object. This must fill in the 178 * read/write/close pointers in the object. The read/write routines 179 * may take an error exit if the specified maximum file size is exceeded. 180 * (If jpeg_mem_available always returns a large value, this routine can 181 * just take an error exit.) 182 */ 183 184EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo, 185 backing_store_ptr info, 186 long total_bytes_needed)); 187 188 189/* 190 * These routines take care of any system-dependent initialization and 191 * cleanup required. jpeg_mem_init will be called before anything is 192 * allocated (and, therefore, nothing in cinfo is of use except the error 193 * manager pointer). It should return a suitable default value for 194 * max_memory_to_use; this may subsequently be overridden by the surrounding 195 * application. (Note that max_memory_to_use is only important if 196 * jpeg_mem_available chooses to consult it ... no one else will.) 197 * jpeg_mem_term may assume that all requested memory has been freed and that 198 * all opened backing-store objects have been closed. 199 */ 200 201EXTERN(size_t) jpeg_mem_init JPP((j_common_ptr cinfo)); 202EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo)); 203