1 /* 2 * jmemsys.h 3 * 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 9 * file. 10 * 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.) 15 * 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. 21 */ 22 23 24 /* 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. 32 */ 33 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, 36 size_t sizeofobject); 37 38 /* 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 43 * large chunks. 44 */ 45 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, 48 size_t sizeofobject); 49 50 /* 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. 56 * 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). 59 */ 60 61 #ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */ 62 #define MAX_ALLOC_CHUNK 1000000000L 63 #endif 64 65 /* 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. 69 * 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. 77 * 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. 82 * 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. 85 */ 86 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); 90 91 92 /* 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. 97 */ 98 99 #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */ 100 101 102 #ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */ 103 104 typedef unsigned short XMSH; /* type of extended-memory handles */ 105 typedef unsigned short EMSH; /* type of expanded-memory handles */ 106 107 typedef union { 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 */ 111 } handle_union; 112 113 #endif /* USE_MSDOS_MEMMGR */ 114 115 #ifdef USE_MAC_MEMMGR /* Mac-specific junk */ 116 #include <Files.h> 117 #endif /* USE_MAC_MEMMGR */ 118 119 120 typedef struct backing_store_struct *backing_store_ptr; 121 122 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, 126 long byte_count); 127 void (*write_backing_store) (j_common_ptr cinfo, backing_store_ptr info, 128 void *buffer_address, long file_offset, 129 long byte_count); 130 void (*close_backing_store) (j_common_ptr cinfo, backing_store_ptr info); 131 132 /* 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 */ 137 #else 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 */ 143 #else 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 */ 147 #endif 148 #endif 149 } backing_store_info; 150 151 152 /* 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.) 158 */ 159 160 EXTERN(void) jpeg_open_backing_store (j_common_ptr cinfo, 161 backing_store_ptr info, 162 long total_bytes_needed); 163 164 165 /* 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. 175 */ 176 177 EXTERN(long) jpeg_mem_init (j_common_ptr cinfo); 178 EXTERN(void) jpeg_mem_term (j_common_ptr cinfo); 179
