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1 /* |
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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 |
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21 |
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22 /* Short forms of external names for systems with brain-damaged linkers. */ |
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23 |
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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 |
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35 |
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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 |
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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 |
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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 |
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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 |
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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 |
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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 |
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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 |
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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 |
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108 |
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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 |
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116 #define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */ |
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117 |
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118 |
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119 #ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */ |
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120 |
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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 |
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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 |
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130 #endif /* USE_MSDOS_MEMMGR */ |
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131 |
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132 #ifdef USE_MAC_MEMMGR /* Mac-specific junk */ |
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133 #include <Files.h> |
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134 #endif /* USE_MAC_MEMMGR */ |
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135 |
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136 |
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137 typedef struct backing_store_struct * backing_store_ptr; |
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138 |
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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 |
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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 |
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171 |
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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 |
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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 |
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184 |
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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 |
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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)); |