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6417 | ashmew2 | 1 | /* |
2 | * jmemansi.c |
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3 | * |
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4 | * Copyright (C) 1992-1996, 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 file provides a simple generic implementation of the system- |
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9 | * dependent portion of the JPEG memory manager. This implementation |
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10 | * assumes that you have the ANSI-standard library routine tmpfile(). |
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11 | * Also, the problem of determining the amount of memory available |
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12 | * is shoved onto the user. |
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13 | */ |
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14 | |||
15 | #define JPEG_INTERNALS |
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16 | #include "jinclude.h" |
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17 | #include "jpeglib.h" |
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18 | #include "jmemsys.h" /* import the system-dependent declarations */ |
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19 | |||
20 | #ifndef HAVE_STDLIB_H /* |
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21 | extern void * malloc JPP((size_t size)); |
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22 | extern void free JPP((void *ptr)); |
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23 | #endif |
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24 | |||
25 | #ifndef SEEK_SET /* pre-ANSI systems may not define this; */ |
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26 | #define SEEK_SET 0 /* if not, assume 0 is correct */ |
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27 | #endif |
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28 | |||
29 | |||
30 | /* |
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31 | * Memory allocation and freeing are controlled by the regular library |
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32 | * routines malloc() and free(). |
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33 | */ |
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34 | |||
35 | GLOBAL(void *) |
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36 | jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject) |
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37 | { |
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38 | return (void *) malloc(sizeofobject); |
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39 | } |
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40 | |||
41 | GLOBAL(void) |
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42 | jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject) |
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43 | { |
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44 | free(object); |
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45 | } |
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46 | |||
47 | |||
48 | /* |
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49 | * "Large" objects are treated the same as "small" ones. |
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50 | * NB: although we include FAR keywords in the routine declarations, |
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51 | * this file won't actually work in 80x86 small/medium model; at least, |
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52 | * you probably won't be able to process useful-size images in only 64KB. |
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53 | */ |
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54 | |||
55 | GLOBAL(void FAR *) |
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56 | jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject) |
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57 | { |
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58 | return (void FAR *) malloc(sizeofobject); |
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59 | } |
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60 | |||
61 | GLOBAL(void) |
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62 | jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject) |
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63 | { |
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64 | free(object); |
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65 | } |
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66 | |||
67 | |||
68 | /* |
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69 | * This routine computes the total memory space available for allocation. |
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70 | * It's impossible to do this in a portable way; our current solution is |
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71 | * to make the user tell us (with a default value set at compile time). |
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72 | * If you can actually get the available space, it's a good idea to subtract |
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73 | * a slop factor of 5% or so. |
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74 | */ |
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75 | |||
76 | #ifndef DEFAULT_MAX_MEM /* so can override from makefile */ |
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77 | #define DEFAULT_MAX_MEM 1000000L /* default: one megabyte */ |
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78 | #endif |
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79 | |||
80 | GLOBAL(long) |
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81 | jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed, |
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82 | long max_bytes_needed, long already_allocated) |
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83 | { |
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84 | return cinfo->mem->max_memory_to_use - already_allocated; |
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85 | } |
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86 | |||
87 | |||
88 | /* |
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89 | * Backing store (temporary file) management. |
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90 | * Backing store objects are only used when the value returned by |
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91 | * jpeg_mem_available is less than the total space needed. You can dispense |
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92 | * with these routines if you have plenty of virtual memory; see jmemnobs.c. |
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93 | */ |
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94 | |||
95 | |||
96 | METHODDEF(void) |
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97 | read_backing_store (j_common_ptr cinfo, backing_store_ptr info, |
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98 | void FAR * buffer_address, |
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99 | long file_offset, long byte_count) |
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100 | { |
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101 | if (fseek(info->temp_file, file_offset, SEEK_SET)) |
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102 | ERREXIT(cinfo, JERR_TFILE_SEEK); |
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103 | if (JFREAD(info->temp_file, buffer_address, byte_count) |
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104 | != (size_t) byte_count) |
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105 | ERREXIT(cinfo, JERR_TFILE_READ); |
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106 | } |
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107 | |||
108 | |||
109 | METHODDEF(void) |
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110 | write_backing_store (j_common_ptr cinfo, backing_store_ptr info, |
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111 | void FAR * buffer_address, |
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112 | long file_offset, long byte_count) |
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113 | { |
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114 | if (fseek(info->temp_file, file_offset, SEEK_SET)) |
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115 | ERREXIT(cinfo, JERR_TFILE_SEEK); |
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116 | if (JFWRITE(info->temp_file, buffer_address, byte_count) |
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117 | != (size_t) byte_count) |
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118 | ERREXIT(cinfo, JERR_TFILE_WRITE); |
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119 | } |
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120 | |||
121 | |||
122 | METHODDEF(void) |
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123 | close_backing_store (j_common_ptr cinfo, backing_store_ptr info) |
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124 | { |
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125 | fclose(info->temp_file); |
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126 | /* Since this implementation uses tmpfile() to create the file, |
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127 | * no explicit file deletion is needed. |
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128 | */ |
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129 | } |
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130 | |||
131 | |||
132 | /* |
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133 | * Initial opening of a backing-store object. |
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134 | * |
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135 | * This version uses tmpfile(), which constructs a suitable file name |
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136 | * behind the scenes. We don't have to use info->temp_name[] at all; |
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137 | * indeed, we can't even find out the actual name of the temp file. |
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138 | */ |
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139 | |||
140 | GLOBAL(void) |
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141 | jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info, |
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142 | long total_bytes_needed) |
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143 | { |
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144 | if ((info->temp_file = tmpfile()) == NULL) |
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145 | ERREXITS(cinfo, JERR_TFILE_CREATE, ""); |
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146 | info->read_backing_store = read_backing_store; |
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147 | info->write_backing_store = write_backing_store; |
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148 | info->close_backing_store = close_backing_store; |
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149 | } |
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150 | |||
151 | |||
152 | /* |
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153 | * These routines take care of any system-dependent initialization and |
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154 | * cleanup required. |
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155 | */ |
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156 | |||
157 | GLOBAL(long) |
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158 | jpeg_mem_init (j_common_ptr cinfo) |
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159 | { |
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160 | return DEFAULT_MAX_MEM; /* default for max_memory_to_use */ |
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161 | } |
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162 | |||
163 | GLOBAL(void) |
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164 | jpeg_mem_term (j_common_ptr cinfo) |
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165 | { |
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166 | /* no work */ |
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167 | } |