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