base/path_service.cc

   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/file_util.h"
  14 #include "base/files/file_path.h"
  15 #include "base/hash_tables.h"
  16 #include "base/lazy_instance.h"
  17 #include "base/logging.h"
  18 #include "base/synchronization/lock.h"
  19
  20 using base::FilePath;
  21
  22 namespace base {
  23   bool PathProvider(int key, FilePath* result);
  24 #if defined(OS_WIN)
  25   bool PathProviderWin(int key, FilePath* result);
  26 #elif defined(OS_MACOSX)
  27   bool PathProviderMac(int key, FilePath* result);
  28 #elif defined(OS_ANDROID)
  29   bool PathProviderAndroid(int key, FilePath* result);
  30 #elif defined(OS_POSIX)
  31   // PathProviderPosix is the default path provider on POSIX OSes other than
  32   // Mac and Android.
  33   bool PathProviderPosix(int key, FilePath* result);
  34 #endif
  35 }
  36
  37 namespace {
  38
  39 typedef base::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   base::PathProvider,
  55   NULL,
  56 #ifndef NDEBUG
  57   base::PATH_START,
  58   base::PATH_END,
  59 #endif
  60   true
  61 };
  62
  63 #if defined(OS_WIN)
  64 Provider base_provider_win = {
  65   base::PathProviderWin,
  66   &base_provider,
  67 #ifndef NDEBUG
  68   base::PATH_WIN_START,
  69   base::PATH_WIN_END,
  70 #endif
  71   true
  72 };
  73 #endif
  74
  75 #if defined(OS_MACOSX)
  76 Provider base_provider_mac = {
  77   base::PathProviderMac,
  78   &base_provider,
  79 #ifndef NDEBUG
  80   base::PATH_MAC_START,
  81   base::PATH_MAC_END,
  82 #endif
  83   true
  84 };
  85 #endif
  86
  87 #if defined(OS_ANDROID)
  88 Provider base_provider_android = {
  89   base::PathProviderAndroid,
  90   &base_provider,
  91 #ifndef NDEBUG
  92   base::PATH_ANDROID_START,
  93   base::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   base::PathProviderPosix,
 102   &base_provider,
 103 #ifndef NDEBUG
 104   base::PATH_POSIX_START,
 105   base::PATH_POSIX_END,
 106 #endif
 107   true
 108 };
 109 #endif
 110
 111
 112 struct PathData {
 113   base::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   ~PathData() {
 132     Provider* p = providers;
 133     while (p) {
 134       Provider* next = p->next;
 135       if (!p->is_static)
 136         delete p;
 137       p = next;
 138     }
 139   }
 140 };
 141
 142 static base::LazyInstance<PathData> g_path_data = LAZY_INSTANCE_INITIALIZER;
 143
 144 static PathData* GetPathData() {
 145   return g_path_data.Pointer();
 146 }
 147
 148 // Tries to find |key| in the cache. |path_data| should be locked by the caller!
 149 bool LockedGetFromCache(int key, const PathData* path_data, FilePath* result) {
 150   if (path_data->cache_disabled)
 151     return false;
 152   // check for a cached version
 153   PathMap::const_iterator it = path_data->cache.find(key);
 154   if (it != path_data->cache.end()) {
 155     *result = it->second;
 156     return true;
 157   }
 158   return false;
 159 }
 160
 161 // Tries to find |key| in the overrides map. |path_data| should be locked by the
 162 // caller!
 163 bool LockedGetFromOverrides(int key, PathData* path_data, FilePath* result) {
 164   // check for an overridden version.
 165   PathMap::const_iterator it = path_data->overrides.find(key);
 166   if (it != path_data->overrides.end()) {
 167     if (!path_data->cache_disabled)
 168       path_data->cache[key] = it->second;
 169     *result = it->second;
 170     return true;
 171   }
 172   return false;
 173 }
 174
 175 }  // namespace
 176
 177 // TODO(brettw): this function does not handle long paths (filename > MAX_PATH)
 178 // characters). This isn't supported very well by Windows right now, so it is
 179 // moot, but we should keep this in mind for the future.
 180 // static
 181 bool PathService::Get(int key, FilePath* result) {
 182   PathData* path_data = GetPathData();
 183   DCHECK(path_data);
 184   DCHECK(result);
 185   DCHECK_GE(key, base::DIR_CURRENT);
 186
 187   // special case the current directory because it can never be cached
 188   if (key == base::DIR_CURRENT)
 189     return file_util::GetCurrentDirectory(result);
 190
 191   Provider* provider = NULL;
 192   {
 193     base::AutoLock scoped_lock(path_data->lock);
 194     if (LockedGetFromCache(key, path_data, result))
 195       return true;
 196
 197     if (LockedGetFromOverrides(key, path_data, result))
 198       return true;
 199
 200     // Get the beginning of the list while it is still locked.
 201     provider = path_data->providers;
 202   }
 203
 204   FilePath path;
 205
 206   // Iterating does not need the lock because only the list head might be
 207   // modified on another thread.
 208   while (provider) {
 209     if (provider->func(key, &path))
 210       break;
 211     DCHECK(path.empty()) << "provider should not have modified path";
 212     provider = provider->next;
 213   }
 214
 215   if (path.empty())
 216     return false;
 217
 218   if (path.ReferencesParent()) {
 219     // Make sure path service never returns a path with ".." in it.
 220     if (!file_util::AbsolutePath(&path)) {
 221       return false;
 222     }
 223   }
 224   *result = path;
 225
 226   base::AutoLock scoped_lock(path_data->lock);
 227   if (!path_data->cache_disabled)
 228     path_data->cache[key] = path;
 229
 230   return true;
 231 }
 232
 233 // static
 234 bool PathService::Override(int key, const FilePath& path) {
 235   // Just call the full function with true for the value of |create|.
 236   return OverrideAndCreateIfNeeded(key, path, true);
 237 }
 238
 239 // static
 240 bool PathService::OverrideAndCreateIfNeeded(int key,
 241                                             const FilePath& path,
 242                                             bool create) {
 243   PathData* path_data = GetPathData();
 244   DCHECK(path_data);
 245   DCHECK_GT(key, base::DIR_CURRENT) << "invalid path key";
 246
 247   FilePath file_path = path;
 248
 249   // For some locations this will fail if called from inside the sandbox there-
 250   // fore we protect this call with a flag.
 251   if (create) {
 252     // Make sure the directory exists. We need to do this before we translate
 253     // this to the absolute path because on POSIX, AbsolutePath fails if called
 254     // on a non-existent path.
 255     if (!file_util::PathExists(file_path) &&
 256         !file_util::CreateDirectory(file_path))
 257       return false;
 258   }
 259
 260   // We need to have an absolute path, as extensions and plugins don't like
 261   // relative paths, and will gladly crash the browser in CHECK()s if they get a
 262   // relative path.
 263   if (!file_util::AbsolutePath(&file_path))
 264     return false;
 265
 266   base::AutoLock scoped_lock(path_data->lock);
 267
 268   // Clear the cache now. Some of its entries could have depended
 269   // on the value we are overriding, and are now out of sync with reality.
 270   path_data->cache.clear();
 271
 272   path_data->overrides[key] = file_path;
 273
 274   return true;
 275 }
 276
 277 // static
 278 bool PathService::RemoveOverride(int key) {
 279   PathData* path_data = GetPathData();
 280   DCHECK(path_data);
 281
 282   base::AutoLock scoped_lock(path_data->lock);
 283
 284   if (path_data->overrides.find(key) == path_data->overrides.end())
 285     return false;
 286
 287   // Clear the cache now. Some of its entries could have depended on the value
 288   // we are going to remove, and are now out of sync.
 289   path_data->cache.clear();
 290
 291   path_data->overrides.erase(key);
 292
 293   return true;
 294 }
 295
 296 // static
 297 void PathService::RegisterProvider(ProviderFunc func, int key_start,
 298                                    int key_end) {
 299   PathData* path_data = GetPathData();
 300   DCHECK(path_data);
 301   DCHECK_GT(key_end, key_start);
 302
 303   Provider* p;
 304
 305   p = new Provider;
 306   p->is_static = false;
 307   p->func = func;
 308 #ifndef NDEBUG
 309   p->key_start = key_start;
 310   p->key_end = key_end;
 311 #endif
 312
 313   base::AutoLock scoped_lock(path_data->lock);
 314
 315 #ifndef NDEBUG
 316   Provider *iter = path_data->providers;
 317   while (iter) {
 318     DCHECK(key_start >= iter->key_end || key_end <= iter->key_start) <<
 319       "path provider collision";
 320     iter = iter->next;
 321   }
 322 #endif
 323
 324   p->next = path_data->providers;
 325   path_data->providers = p;
 326 }
 327
 328 // static
 329 void PathService::DisableCache() {
 330   PathData* path_data = GetPathData();
 331   DCHECK(path_data);
 332
 333   base::AutoLock scoped_lock(path_data->lock);
 334   path_data->cache.clear();
 335   path_data->cache_disabled = true;
 336 }