1 | /* $Id: imagecache.c 3195 2018-03-27 18:09:23Z bird $ */
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2 | /** @file
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3 | * kBuild specific executable image cache for Windows.
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4 | */
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5 |
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6 | /*
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7 | * Copyright (c) 2012 knut st. osmundsen <bird-kBuild-spamx@anduin.net>
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8 | *
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9 | * This file is part of kBuild.
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10 | *
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11 | * kBuild is free software; you can redistribute it and/or modify
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12 | * it under the terms of the GNU General Public License as published by
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13 | * the Free Software Foundation; either version 3 of the License, or
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14 | * (at your option) any later version.
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15 | *
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16 | * kBuild is distributed in the hope that it will be useful,
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17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 | * GNU General Public License for more details.
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20 | *
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21 | * You should have received a copy of the GNU General Public License
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22 | * along with kBuild. If not, see <http://www.gnu.org/licenses/>
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23 | *
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24 | */
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25 |
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26 | /* No GNU coding style here! */
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27 |
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28 | /*********************************************************************************************************************************
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29 | * Header Files *
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30 | *********************************************************************************************************************************/
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31 | #include "makeint.h"
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32 |
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33 | #include <Windows.h>
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34 |
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35 |
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36 | /*********************************************************************************************************************************
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37 | * Structures and Typedefs *
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38 | *********************************************************************************************************************************/
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39 | typedef struct EXECCACHEENTRY
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40 | {
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41 | /** The name hash value. */
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42 | unsigned uHash;
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43 | /** The name length. */
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44 | unsigned cwcName;
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45 | /** Pointer to the next name with the same hash. */
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46 | struct EXECCACHEENTRY *pNext;
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47 | /** When it was last referenced. */
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48 | unsigned uLastRef;
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49 | /** The module handle, LOAD_LIBRARY_AS_DATAFILE. */
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50 | HMODULE hmod1;
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51 | /** The module handle, DONT_RESOLVE_DLL_REFERENCES. */
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52 | HMODULE hmod2;
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53 | /** The executable path. */
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54 | wchar_t wszName[1];
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55 | } EXECCACHEENTRY;
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56 | typedef EXECCACHEENTRY *PEXECCACHEENTRY;
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57 |
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58 |
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59 | /*********************************************************************************************************************************
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60 | * Global Variables *
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61 | *********************************************************************************************************************************/
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62 | /** Critical section serializing all access. */
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63 | static CRITICAL_SECTION g_CritSect;
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64 | /** Set if initialized. */
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65 | static int volatile g_fInitialized = 0;
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66 | /** The number of cached images. */
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67 | static unsigned g_cCached;
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68 | /** Used noting when entries was last used.
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69 | * Increased on each kmk_cache_exec_image call. */
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70 | static unsigned g_uNow;
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71 |
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72 | /** The size of the hash table. */
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73 | #define EXECCACHE_HASHTAB_SIZE 128
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74 | /** The hash table. */
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75 | static PEXECCACHEENTRY g_apHashTab[EXECCACHE_HASHTAB_SIZE];
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76 |
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77 |
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78 | /** A sleepy approach to do-once. */
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79 | static void kmk_cache_lazy_init(void)
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80 | {
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81 | if (_InterlockedCompareExchange(&g_fInitialized, -1, 0) == 0)
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82 | {
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83 | InitializeCriticalSection(&g_CritSect);
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84 | _InterlockedExchange(&g_fInitialized, 1);
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85 | }
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86 | else
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87 | while (g_fInitialized != 1)
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88 | Sleep(1);
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89 | }
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90 |
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91 |
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92 | /* sdbm:
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93 | This algorithm was created for sdbm (a public-domain reimplementation of
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94 | ndbm) database library. it was found to do well in scrambling bits,
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95 | causing better distribution of the keys and fewer splits. it also happens
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96 | to be a good general hashing function with good distribution. the actual
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97 | function is hash(i) = hash(i - 1) * 65599 + str[i]; what is included below
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98 | is the faster version used in gawk. [there is even a faster, duff-device
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99 | version] the magic constant 65599 was picked out of thin air while
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100 | experimenting with different constants, and turns out to be a prime.
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101 | this is one of the algorithms used in berkeley db (see sleepycat) and
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102 | elsewhere. */
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103 |
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104 | static unsigned execcache_calc_hash(const wchar_t *pwsz, size_t *pcch)
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105 | {
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106 | wchar_t const * const pwszStart = pwsz;
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107 | unsigned hash = 0;
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108 | int ch;
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109 |
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110 | while ((ch = *pwsz++) != L'\0')
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111 | hash = ch + (hash << 6) + (hash << 16) - hash;
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112 |
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113 | *pcch = (size_t)(pwsz - pwszStart - 1);
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114 | return hash;
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115 | }
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116 |
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117 | /**
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118 | * Caches two memory mappings of the specified image so that it isn't flushed
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119 | * from the kernel's cache mananger.
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120 | *
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121 | * Not sure exactly how much this actually helps, but whatever...
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122 | *
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123 | * @param pwszExec The executable.
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124 | */
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125 | extern void kmk_cache_exec_image_w(const wchar_t *pwszExec)
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126 | {
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127 | /*
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128 | * Prepare name lookup and to lazy init.
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129 | */
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130 | size_t cwcName;
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131 | const unsigned uHash = execcache_calc_hash(pwszExec, &cwcName);
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132 | PEXECCACHEENTRY *ppCur = &g_apHashTab[uHash % EXECCACHE_HASHTAB_SIZE];
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133 | PEXECCACHEENTRY pCur;
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134 |
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135 | if (g_fInitialized != 1)
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136 | kmk_cache_lazy_init();
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137 |
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138 | /*
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139 | * Do the lookup.
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140 | */
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141 | EnterCriticalSection(&g_CritSect);
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142 | pCur = *ppCur;
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143 | while (pCur)
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144 | {
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145 | if ( pCur->uHash == uHash
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146 | && pCur->cwcName == cwcName
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147 | && !memcmp(pCur->wszName, pwszExec, cwcName * sizeof(wchar_t)))
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148 | {
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149 | pCur->uLastRef = ++g_uNow;
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150 | LeaveCriticalSection(&g_CritSect);
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151 | return;
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152 | }
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153 | ppCur = &pCur->pNext;
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154 | pCur = pCur->pNext;
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155 | }
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156 | LeaveCriticalSection(&g_CritSect);
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157 |
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158 | /*
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159 | * Not found, create a new entry.
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160 | */
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161 | pCur = xmalloc(sizeof(*pCur) + cwcName * sizeof(wchar_t));
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162 | pCur->uHash = uHash;
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163 | pCur->cwcName = (unsigned)cwcName;
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164 | pCur->pNext = NULL;
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165 | pCur->uLastRef = ++g_uNow;
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166 | memcpy(pCur->wszName, pwszExec, (cwcName + 1) * sizeof(wchar_t));
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167 | pCur->hmod1 = LoadLibraryExW(pwszExec, NULL, LOAD_LIBRARY_AS_DATAFILE);
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168 | if (pCur->hmod1 != NULL)
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169 | pCur->hmod2 = LoadLibraryExW(pwszExec, NULL, DONT_RESOLVE_DLL_REFERENCES);
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170 | else
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171 | pCur->hmod2 = NULL;
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172 |
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173 | /*
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174 | * Insert it.
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175 | * Take into account that we might've been racing other threads,
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176 | * fortunately we don't evict anything from the cache.
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177 | */
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178 | EnterCriticalSection(&g_CritSect);
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179 | if (*ppCur != NULL)
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180 | {
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181 | /* Find new end of chain and check for duplicate. */
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182 | PEXECCACHEENTRY pCur2 = *ppCur;
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183 | while (pCur2)
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184 | {
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185 | if ( pCur->uHash == uHash
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186 | && pCur->cwcName == cwcName
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187 | && !memcmp(pCur->wszName, pwszExec, cwcName * sizeof(wchar_t)))
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188 | break;
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189 | ppCur = &pCur->pNext;
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190 | pCur = pCur->pNext;
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191 | }
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192 |
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193 | }
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194 | if (*ppCur == NULL)
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195 | {
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196 | *ppCur = pCur;
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197 | g_cCached++;
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198 | LeaveCriticalSection(&g_CritSect);
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199 | }
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200 | else
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201 | {
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202 | LeaveCriticalSection(&g_CritSect);
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203 |
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204 | if (pCur->hmod1 != NULL)
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205 | FreeLibrary(pCur->hmod1);
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206 | if (pCur->hmod2 != NULL)
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207 | FreeLibrary(pCur->hmod2);
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208 | free(pCur);
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209 | }
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210 | }
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211 |
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212 | extern void kmk_cache_exec_image_a(const char *pszExec)
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213 | {
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214 | wchar_t wszExec[260];
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215 | int cwc = MultiByteToWideChar(CP_ACP, 0 /*fFlags*/, pszExec, strlen(pszExec) + 1, wszExec, 260);
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216 | if (cwc > 0)
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217 | kmk_cache_exec_image_w(wszExec);
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218 | }
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219 |
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