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/containers/hash_tables.h"
  14 #include "base/file_util.h"
  15 #include "base/files/file_path.h"
  16 #include "base/lazy_instance.h"
  17 #include "base/logging.h"
  18 #include "base/synchronization/lock.h"
  19
  20 using base::FilePath;
  21 using base::MakeAbsoluteFilePath;
  22
  23 namespace base {
  24   bool PathProvider(int key, FilePath* result);
  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
  38 namespace {
  39
  40 typedef base::hash_map<int, FilePath> PathMap;
  41
  42 // We keep a linked list of providers.  In a debug build we ensure that no two
  43 // providers claim overlapping keys.
  44 struct Provider {
  45   PathService::ProviderFunc func;
  46   struct Provider* next;
  47 #ifndef NDEBUG
  48   int key_start;
  49   int key_end;
  50 #endif
  51   bool is_static;
  52 };
  53
  54 Provider base_provider = {
  55   base::PathProvider,
  56   NULL,
  57 #ifndef NDEBUG
  58   base::PATH_START,
  59   base::PATH_END,
  60 #endif
  61   true
  62 };
  63
  64 #if defined(OS_WIN)
  65 Provider base_provider_win = {
  66   base::PathProviderWin,
  67   &base_provider,
  68 #ifndef NDEBUG
  69   base::PATH_WIN_START,
  70   base::PATH_WIN_END,
  71 #endif
  72   true
  73 };
  74 #endif
  75
  76 #if defined(OS_MACOSX)
  77 Provider base_provider_mac = {
  78   base::PathProviderMac,
  79   &base_provider,
  80 #ifndef NDEBUG
  81   base::PATH_MAC_START,
  82   base::PATH_MAC_END,
  83 #endif
  84   true
  85 };
  86 #endif
  87
  88 #if defined(OS_ANDROID)
  89 Provider base_provider_android = {
  90   base::PathProviderAndroid,
  91   &base_provider,
  92 #ifndef NDEBUG
  93   base::PATH_ANDROID_START,
  94   base::PATH_ANDROID_END,
  95 #endif
  96   true
  97 };
  98 #endif
  99
 100 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
 101 Provider base_provider_posix = {
 102   base::PathProviderPosix,
 103   &base_provider,
 104 #ifndef NDEBUG
 105   base::PATH_POSIX_START,
 106   base::PATH_POSIX_END,
 107 #endif
 108   true
 109 };
 110 #endif
 111
 112
 113 struct PathData {
 114   base::Lock lock;
 115   PathMap cache;        // Cache mappings from path key to path value.
 116   PathMap overrides;    // Track path overrides.
 117   Provider* providers;  // Linked list of path service providers.
 118   bool cache_disabled;  // Don't use cache if true;
 119
 120   PathData() : cache_disabled(false) {
 121 #if defined(OS_WIN)
 122     providers = &base_provider_win;
 123 #elif defined(OS_MACOSX)
 124     providers = &base_provider_mac;
 125 #elif defined(OS_ANDROID)
 126     providers = &base_provider_android;
 127 #elif defined(OS_POSIX)
 128     providers = &base_provider_posix;
 129 #endif
 130   }
 131
 132   ~PathData() {
 133     Provider* p = providers;
 134     while (p) {
 135       Provider* next = p->next;
 136       if (!p->is_static)
 137         delete p;
 138       p = next;
 139     }
 140   }
 141 };
 142
 143 static base::LazyInstance<PathData> g_path_data = LAZY_INSTANCE_INITIALIZER;
 144
 145 static PathData* GetPathData() {
 146   return g_path_data.Pointer();
 147 }
 148
 149 // Tries to find |key| in the cache. |path_data| should be locked by the caller!
 150 bool LockedGetFromCache(int key, const PathData* path_data, FilePath* result) {
 151   if (path_data->cache_disabled)
 152     return false;
 153   // check for a cached version
 154   PathMap::const_iterator it = path_data->cache.find(key);
 155   if (it != path_data->cache.end()) {
 156     *result = it->second;
 157     return true;
 158   }
 159   return false;
 160 }
 161
 162 // Tries to find |key| in the overrides map. |path_data| should be locked by the
 163 // caller!
 164 bool LockedGetFromOverrides(int key, PathData* path_data, FilePath* result) {
 165   // check for an overridden version.
 166   PathMap::const_iterator it = path_data->overrides.find(key);
 167   if (it != path_data->overrides.end()) {
 168     if (!path_data->cache_disabled)
 169       path_data->cache[key] = it->second;
 170     *result = it->second;
 171     return true;
 172   }
 173   return false;
 174 }
 175
 176 }  // namespace
 177
 178 // TODO(brettw): this function does not handle long paths (filename > MAX_PATH)
 179 // characters). This isn't supported very well by Windows right now, so it is
 180 // moot, but we should keep this in mind for the future.
 181 // static
 182 bool PathService::Get(int key, FilePath* result) {
 183   PathData* path_data = GetPathData();
 184   DCHECK(path_data);
 185   DCHECK(result);
 186   DCHECK_GE(key, base::DIR_CURRENT);
 187
 188   // special case the current directory because it can never be cached
 189   if (key == base::DIR_CURRENT)
 190     return base::GetCurrentDirectory(result);
 191
 192   Provider* provider = NULL;
 193   {
 194     base::AutoLock scoped_lock(path_data->lock);
 195     if (LockedGetFromCache(key, path_data, result))
 196       return true;
 197
 198     if (LockedGetFromOverrides(key, path_data, result))
 199       return true;
 200
 201     // Get the beginning of the list while it is still locked.
 202     provider = path_data->providers;
 203   }
 204
 205   FilePath path;
 206
 207   // Iterating does not need the lock because only the list head might be
 208   // modified on another thread.
 209   while (provider) {
 210     if (provider->func(key, &path))
 211       break;
 212     DCHECK(path.empty()) << "provider should not have modified path";
 213     provider = provider->next;
 214   }
 215
 216   if (path.empty())
 217     return false;
 218
 219   if (path.ReferencesParent()) {
 220     // Make sure path service never returns a path with ".." in it.
 221     path = MakeAbsoluteFilePath(path);
 222     if (path.empty())
 223       return false;
 224   }
 225   *result = path;
 226
 227   base::AutoLock scoped_lock(path_data->lock);
 228   if (!path_data->cache_disabled)
 229     path_data->cache[key] = path;
 230
 231   return true;
 232 }
 233
 234 // static
 235 bool PathService::Override(int key, const FilePath& path) {
 236   // Just call the full function with true for the value of |create|.
 237   return OverrideAndCreateIfNeeded(key, path, true);
 238 }
 239
 240 // static
 241 bool PathService::OverrideAndCreateIfNeeded(int key,
 242                                             const FilePath& path,
 243                                             bool create) {
 244   PathData* path_data = GetPathData();
 245   DCHECK(path_data);
 246   DCHECK_GT(key, base::DIR_CURRENT) << "invalid path key";
 247
 248   FilePath file_path = path;
 249
 250   // For some locations this will fail if called from inside the sandbox there-
 251   // fore we protect this call with a flag.
 252   if (create) {
 253     // Make sure the directory exists. We need to do this before we translate
 254     // this to the absolute path because on POSIX, MakeAbsoluteFilePath fails
 255     // if called on a non-existent path.
 256     if (!base::PathExists(file_path) &&
 257         !base::CreateDirectory(file_path))
 258       return false;
 259   }
 260
 261   // We need to have an absolute path.
 262   file_path = MakeAbsoluteFilePath(file_path);
 263   if (file_path.empty())
 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 }