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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 6417 | ashmew2 | 1 | /* |
| 2 | * jmemsys.h |
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| 3 | * |
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| 4 | * Copyright (C) 1992-1997, Thomas G. Lane. |
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| 5 | * This file is part of the Independent JPEG Group's software. |
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| 6 | * For conditions of distribution and use, see the accompanying README file. |
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| 7 | * |
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| 8 | * This include file defines the interface between the system-independent |
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| 9 | * and system-dependent portions of the JPEG memory manager. No other |
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| 10 | * modules need include it. (The system-independent portion is jmemmgr.c; |
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| 11 | * there are several different versions of the system-dependent portion.) |
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| 12 | * |
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| 13 | * This file works as-is for the system-dependent memory managers supplied |
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| 14 | * in the IJG distribution. You may need to modify it if you write a |
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| 15 | * custom memory manager. If system-dependent changes are needed in |
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| 16 | * this file, the best method is to #ifdef them based on a configuration |
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| 17 | * symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR |
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| 18 | * and USE_MAC_MEMMGR. |
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| 19 | */ |
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| 20 | |||
| 21 | |||
| 22 | /* Short forms of external names for systems with brain-damaged linkers. */ |
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| 23 | |||
| 24 | #ifdef NEED_SHORT_EXTERNAL_NAMES |
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| 25 | #define jpeg_get_small jGetSmall |
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| 26 | #define jpeg_free_small jFreeSmall |
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| 27 | #define jpeg_get_large jGetLarge |
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| 28 | #define jpeg_free_large jFreeLarge |
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| 29 | #define jpeg_mem_available jMemAvail |
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| 30 | #define jpeg_open_backing_store jOpenBackStore |
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| 31 | #define jpeg_mem_init jMemInit |
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| 32 | #define jpeg_mem_term jMemTerm |
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| 33 | #endif /* NEED_SHORT_EXTERNAL_NAMES */ |
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| 34 | |||
| 35 | |||
| 36 | /* |
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| 37 | * These two functions are used to allocate and release small chunks of |
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| 38 | * memory. (Typically the total amount requested through jpeg_get_small is |
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| 39 | * no more than 20K or so; this will be requested in chunks of a few K each.) |
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| 40 | * Behavior should be the same as for the standard library functions malloc |
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| 41 | * and free; in particular, jpeg_get_small must return NULL on failure. |
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| 42 | * On most systems, these ARE malloc and free. jpeg_free_small is passed the |
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| 43 | * size of the object being freed, just in case it's needed. |
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| 44 | * On an 80x86 machine using small-data memory model, these manage near heap. |
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| 45 | */ |
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| 46 | |||
| 47 | EXTERN(void *) jpeg_get_small JPP((j_common_ptr cinfo, size_t sizeofobject)); |
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| 48 | EXTERN(void) jpeg_free_small JPP((j_common_ptr cinfo, void * object, |
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| 49 | size_t sizeofobject)); |
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| 50 | |||
| 51 | /* |
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| 52 | * These two functions are used to allocate and release large chunks of |
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| 53 | * memory (up to the total free space designated by jpeg_mem_available). |
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| 54 | * The interface is the same as above, except that on an 80x86 machine, |
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| 55 | * far pointers are used. On most other machines these are identical to |
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| 56 | * the jpeg_get/free_small routines; but we keep them separate anyway, |
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| 57 | * in case a different allocation strategy is desirable for large chunks. |
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| 58 | */ |
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| 59 | |||
| 60 | EXTERN(void FAR *) jpeg_get_large JPP((j_common_ptr cinfo, |
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| 61 | size_t sizeofobject)); |
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| 62 | EXTERN(void) jpeg_free_large JPP((j_common_ptr cinfo, void FAR * object, |
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| 63 | size_t sizeofobject)); |
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| 64 | |||
| 65 | /* |
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| 66 | * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may |
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| 67 | * be requested in a single call to jpeg_get_large (and jpeg_get_small for that |
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| 68 | * matter, but that case should never come into play). This macro is needed |
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| 69 | * to model the 64Kb-segment-size limit of far addressing on 80x86 machines. |
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| 70 | * On those machines, we expect that jconfig.h will provide a proper value. |
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| 71 | * On machines with 32-bit flat address spaces, any large constant may be used. |
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| 72 | * |
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| 73 | * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type |
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| 74 | * size_t and will be a multiple of sizeof(align_type). |
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| 75 | */ |
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| 76 | |||
| 77 | #ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */ |
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| 78 | #define MAX_ALLOC_CHUNK 1000000000L |
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| 79 | #endif |
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| 80 | |||
| 81 | /* |
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| 82 | * This routine computes the total space still available for allocation by |
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| 83 | * jpeg_get_large. If more space than this is needed, backing store will be |
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| 84 | * used. NOTE: any memory already allocated must not be counted. |
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| 85 | * |
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| 86 | * There is a minimum space requirement, corresponding to the minimum |
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| 87 | * feasible buffer sizes; jmemmgr.c will request that much space even if |
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| 88 | * jpeg_mem_available returns zero. The maximum space needed, enough to hold |
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| 89 | * all working storage in memory, is also passed in case it is useful. |
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| 90 | * Finally, the total space already allocated is passed. If no better |
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| 91 | * method is available, cinfo->mem->max_memory_to_use - already_allocated |
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| 92 | * is often a suitable calculation. |
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| 93 | * |
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| 94 | * It is OK for jpeg_mem_available to underestimate the space available |
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| 95 | * (that'll just lead to more backing-store access than is really necessary). |
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| 96 | * However, an overestimate will lead to failure. Hence it's wise to subtract |
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| 97 | * a slop factor from the true available space. 5% should be enough. |
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| 98 | * |
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| 99 | * On machines with lots of virtual memory, any large constant may be returned. |
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| 100 | * Conversely, zero may be returned to always use the minimum amount of memory. |
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| 101 | */ |
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| 102 | |||
| 103 | EXTERN(long) jpeg_mem_available JPP((j_common_ptr cinfo, |
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| 104 | long min_bytes_needed, |
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| 105 | long max_bytes_needed, |
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| 106 | long already_allocated)); |
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| 107 | |||
| 108 | |||
| 109 | /* |
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| 110 | * This structure holds whatever state is needed to access a single |
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| 111 | * backing-store object. The read/write/close method pointers are called |
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| 112 | * by jmemmgr.c to manipulate the backing-store object; all other fields |
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| 113 | * are private to the system-dependent backing store routines. |
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| 114 | */ |
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| 115 | |||
| 116 | #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */ |
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| 117 | |||
| 118 | |||
| 119 | #ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */ |
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| 120 | |||
| 121 | typedef unsigned short XMSH; /* type of extended-memory handles */ |
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| 122 | typedef unsigned short EMSH; /* type of expanded-memory handles */ |
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| 123 | |||
| 124 | typedef union { |
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| 125 | short file_handle; /* DOS file handle if it's a temp file */ |
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| 126 | XMSH xms_handle; /* handle if it's a chunk of XMS */ |
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| 127 | EMSH ems_handle; /* handle if it's a chunk of EMS */ |
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| 128 | } handle_union; |
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| 129 | |||
| 130 | #endif /* USE_MSDOS_MEMMGR */ |
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| 131 | |||
| 132 | #ifdef USE_MAC_MEMMGR /* Mac-specific junk */ |
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| 133 | #include |
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| 134 | #endif /* USE_MAC_MEMMGR */ |
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| 135 | |||
| 136 | |||
| 137 | typedef struct backing_store_struct * backing_store_ptr; |
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| 138 | |||
| 139 | typedef struct backing_store_struct { |
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| 140 | /* Methods for reading/writing/closing this backing-store object */ |
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| 141 | JMETHOD(void, read_backing_store, (j_common_ptr cinfo, |
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| 142 | backing_store_ptr info, |
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| 143 | void FAR * buffer_address, |
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| 144 | long file_offset, long byte_count)); |
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| 145 | JMETHOD(void, write_backing_store, (j_common_ptr cinfo, |
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| 146 | backing_store_ptr info, |
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| 147 | void FAR * buffer_address, |
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| 148 | long file_offset, long byte_count)); |
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| 149 | JMETHOD(void, close_backing_store, (j_common_ptr cinfo, |
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| 150 | backing_store_ptr info)); |
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| 151 | |||
| 152 | /* Private fields for system-dependent backing-store management */ |
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| 153 | #ifdef USE_MSDOS_MEMMGR |
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| 154 | /* For the MS-DOS manager (jmemdos.c), we need: */ |
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| 155 | handle_union handle; /* reference to backing-store storage object */ |
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| 156 | char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */ |
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| 157 | #else |
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| 158 | #ifdef USE_MAC_MEMMGR |
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| 159 | /* For the Mac manager (jmemmac.c), we need: */ |
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| 160 | short temp_file; /* file reference number to temp file */ |
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| 161 | FSSpec tempSpec; /* the FSSpec for the temp file */ |
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| 162 | char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */ |
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| 163 | #else |
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| 164 | /* For a typical implementation with temp files, we need: */ |
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| 165 | FILE * temp_file; /* stdio reference to temp file */ |
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| 166 | char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */ |
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| 167 | #endif |
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| 168 | #endif |
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| 169 | } backing_store_info; |
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| 170 | |||
| 171 | |||
| 172 | /* |
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| 173 | * Initial opening of a backing-store object. This must fill in the |
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| 174 | * read/write/close pointers in the object. The read/write routines |
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| 175 | * may take an error exit if the specified maximum file size is exceeded. |
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| 176 | * (If jpeg_mem_available always returns a large value, this routine can |
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| 177 | * just take an error exit.) |
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| 178 | */ |
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| 179 | |||
| 180 | EXTERN(void) jpeg_open_backing_store JPP((j_common_ptr cinfo, |
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| 181 | backing_store_ptr info, |
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| 182 | long total_bytes_needed)); |
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| 183 | |||
| 184 | |||
| 185 | /* |
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| 186 | * These routines take care of any system-dependent initialization and |
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| 187 | * cleanup required. jpeg_mem_init will be called before anything is |
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| 188 | * allocated (and, therefore, nothing in cinfo is of use except the error |
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| 189 | * manager pointer). It should return a suitable default value for |
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| 190 | * max_memory_to_use; this may subsequently be overridden by the surrounding |
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| 191 | * application. (Note that max_memory_to_use is only important if |
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| 192 | * jpeg_mem_available chooses to consult it ... no one else will.) |
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| 193 | * jpeg_mem_term may assume that all requested memory has been freed and that |
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| 194 | * all opened backing-store objects have been closed. |
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| 195 | */ |
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| 196 | |||
| 197 | EXTERN(long) jpeg_mem_init JPP((j_common_ptr cinfo)); |
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| 198 | EXTERN(void) jpeg_mem_term JPP((j_common_ptr cinfo)); |