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