1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "base/path_service.h" 6 7 #if defined(OS_WIN) 8 #include <windows.h> 9 #include <shellapi.h> 10 #include <shlobj.h> 11 #endif 12 13 #include "base/containers/hash_tables.h" 14 #include "base/files/file_path.h" 15 #include "base/files/file_util.h" 16 #include "base/lazy_instance.h" 17 #include "base/logging.h" 18 #include "base/synchronization/lock.h" 19 #include "build/build_config.h" 20 21 namespace base { 22 23 bool PathProvider(int key, FilePath* result); 24 25 #if defined(OS_WIN) 26 bool PathProviderWin(int key, FilePath* result); 27 #elif defined(OS_MACOSX) 28 bool PathProviderMac(int key, FilePath* result); 29 #elif defined(OS_ANDROID) 30 bool PathProviderAndroid(int key, FilePath* result); 31 #elif defined(OS_POSIX) 32 // PathProviderPosix is the default path provider on POSIX OSes other than 33 // Mac and Android. 34 bool PathProviderPosix(int key, FilePath* result); 35 #endif 36 37 namespace { 38 39 typedef hash_map<int, FilePath> PathMap; 40 41 // We keep a linked list of providers. In a debug build we ensure that no two 42 // providers claim overlapping keys. 43 struct Provider { 44 PathService::ProviderFunc func; 45 struct Provider* next; 46 #ifndef NDEBUG 47 int key_start; 48 int key_end; 49 #endif 50 bool is_static; 51 }; 52 53 Provider base_provider = { 54 PathProvider, 55 NULL, 56 #ifndef NDEBUG 57 PATH_START, 58 PATH_END, 59 #endif 60 true 61 }; 62 63 #if defined(OS_WIN) 64 Provider base_provider_win = { 65 PathProviderWin, 66 &base_provider, 67 #ifndef NDEBUG 68 PATH_WIN_START, 69 PATH_WIN_END, 70 #endif 71 true 72 }; 73 #endif 74 75 #if defined(OS_MACOSX) 76 Provider base_provider_mac = { 77 PathProviderMac, 78 &base_provider, 79 #ifndef NDEBUG 80 PATH_MAC_START, 81 PATH_MAC_END, 82 #endif 83 true 84 }; 85 #endif 86 87 #if defined(OS_ANDROID) 88 Provider base_provider_android = { 89 PathProviderAndroid, 90 &base_provider, 91 #ifndef NDEBUG 92 PATH_ANDROID_START, 93 PATH_ANDROID_END, 94 #endif 95 true 96 }; 97 #endif 98 99 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID) 100 Provider base_provider_posix = { 101 PathProviderPosix, 102 &base_provider, 103 #ifndef NDEBUG 104 PATH_POSIX_START, 105 PATH_POSIX_END, 106 #endif 107 true 108 }; 109 #endif 110 111 112 struct PathData { 113 Lock lock; 114 PathMap cache; // Cache mappings from path key to path value. 115 PathMap overrides; // Track path overrides. 116 Provider* providers; // Linked list of path service providers. 117 bool cache_disabled; // Don't use cache if true; 118 119 PathData() : cache_disabled(false) { 120 #if defined(OS_WIN) 121 providers = &base_provider_win; 122 #elif defined(OS_MACOSX) 123 providers = &base_provider_mac; 124 #elif defined(OS_ANDROID) 125 providers = &base_provider_android; 126 #elif defined(OS_POSIX) 127 providers = &base_provider_posix; 128 #endif 129 } 130 }; 131 132 static LazyInstance<PathData>::Leaky g_path_data = LAZY_INSTANCE_INITIALIZER; 133 134 static PathData* GetPathData() { 135 return g_path_data.Pointer(); 136 } 137 138 // Tries to find |key| in the cache. |path_data| should be locked by the caller! 139 bool LockedGetFromCache(int key, const PathData* path_data, FilePath* result) { 140 if (path_data->cache_disabled) 141 return false; 142 // check for a cached version 143 PathMap::const_iterator it = path_data->cache.find(key); 144 if (it != path_data->cache.end()) { 145 *result = it->second; 146 return true; 147 } 148 return false; 149 } 150 151 // Tries to find |key| in the overrides map. |path_data| should be locked by the 152 // caller! 153 bool LockedGetFromOverrides(int key, PathData* path_data, FilePath* result) { 154 // check for an overridden version. 155 PathMap::const_iterator it = path_data->overrides.find(key); 156 if (it != path_data->overrides.end()) { 157 if (!path_data->cache_disabled) 158 path_data->cache[key] = it->second; 159 *result = it->second; 160 return true; 161 } 162 return false; 163 } 164 165 } // namespace 166 167 // TODO(brettw): this function does not handle long paths (filename > MAX_PATH) 168 // characters). This isn't supported very well by Windows right now, so it is 169 // moot, but we should keep this in mind for the future. 170 // static 171 bool PathService::Get(int key, FilePath* result) { 172 PathData* path_data = GetPathData(); 173 DCHECK(path_data); 174 DCHECK(result); 175 DCHECK_GE(key, DIR_CURRENT); 176 177 // special case the current directory because it can never be cached 178 if (key == DIR_CURRENT) 179 return GetCurrentDirectory(result); 180 181 Provider* provider = NULL; 182 { 183 AutoLock scoped_lock(path_data->lock); 184 if (LockedGetFromCache(key, path_data, result)) 185 return true; 186 187 if (LockedGetFromOverrides(key, path_data, result)) 188 return true; 189 190 // Get the beginning of the list while it is still locked. 191 provider = path_data->providers; 192 } 193 194 FilePath path; 195 196 // Iterating does not need the lock because only the list head might be 197 // modified on another thread. 198 while (provider) { 199 if (provider->func(key, &path)) 200 break; 201 DCHECK(path.empty()) << "provider should not have modified path"; 202 provider = provider->next; 203 } 204 205 if (path.empty()) 206 return false; 207 208 if (path.ReferencesParent()) { 209 // Make sure path service never returns a path with ".." in it. 210 path = MakeAbsoluteFilePath(path); 211 if (path.empty()) 212 return false; 213 } 214 *result = path; 215 216 AutoLock scoped_lock(path_data->lock); 217 if (!path_data->cache_disabled) 218 path_data->cache[key] = path; 219 220 return true; 221 } 222 223 // static 224 bool PathService::Override(int key, const FilePath& path) { 225 // Just call the full function with true for the value of |create|, and 226 // assume that |path| may not be absolute yet. 227 return OverrideAndCreateIfNeeded(key, path, false, true); 228 } 229 230 // static 231 bool PathService::OverrideAndCreateIfNeeded(int key, 232 const FilePath& path, 233 bool is_absolute, 234 bool create) { 235 PathData* path_data = GetPathData(); 236 DCHECK(path_data); 237 DCHECK_GT(key, DIR_CURRENT) << "invalid path key"; 238 239 FilePath file_path = path; 240 241 // For some locations this will fail if called from inside the sandbox there- 242 // fore we protect this call with a flag. 243 if (create) { 244 // Make sure the directory exists. We need to do this before we translate 245 // this to the absolute path because on POSIX, MakeAbsoluteFilePath fails 246 // if called on a non-existent path. 247 if (!PathExists(file_path) && !CreateDirectory(file_path)) 248 return false; 249 } 250 251 // We need to have an absolute path. 252 if (!is_absolute) { 253 file_path = MakeAbsoluteFilePath(file_path); 254 if (file_path.empty()) 255 return false; 256 } 257 DCHECK(file_path.IsAbsolute()); 258 259 AutoLock scoped_lock(path_data->lock); 260 261 // Clear the cache now. Some of its entries could have depended 262 // on the value we are overriding, and are now out of sync with reality. 263 path_data->cache.clear(); 264 265 path_data->overrides[key] = file_path; 266 267 return true; 268 } 269 270 // static 271 bool PathService::RemoveOverride(int key) { 272 PathData* path_data = GetPathData(); 273 DCHECK(path_data); 274 275 AutoLock scoped_lock(path_data->lock); 276 277 if (path_data->overrides.find(key) == path_data->overrides.end()) 278 return false; 279 280 // Clear the cache now. Some of its entries could have depended on the value 281 // we are going to remove, and are now out of sync. 282 path_data->cache.clear(); 283 284 path_data->overrides.erase(key); 285 286 return true; 287 } 288 289 // static 290 void PathService::RegisterProvider(ProviderFunc func, int key_start, 291 int key_end) { 292 PathData* path_data = GetPathData(); 293 DCHECK(path_data); 294 DCHECK_GT(key_end, key_start); 295 296 Provider* p; 297 298 p = new Provider; 299 p->is_static = false; 300 p->func = func; 301 #ifndef NDEBUG 302 p->key_start = key_start; 303 p->key_end = key_end; 304 #endif 305 306 AutoLock scoped_lock(path_data->lock); 307 308 #ifndef NDEBUG 309 Provider *iter = path_data->providers; 310 while (iter) { 311 DCHECK(key_start >= iter->key_end || key_end <= iter->key_start) << 312 "path provider collision"; 313 iter = iter->next; 314 } 315 #endif 316 317 p->next = path_data->providers; 318 path_data->providers = p; 319 } 320 321 // static 322 void PathService::DisableCache() { 323 PathData* path_data = GetPathData(); 324 DCHECK(path_data); 325 326 AutoLock scoped_lock(path_data->lock); 327 path_data->cache.clear(); 328 path_data->cache_disabled = true; 329 } 330 331 } // namespace base 332
