base/path_service.h

   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 #ifndef BASE_PATH_SERVICE_H_
   6 #define BASE_PATH_SERVICE_H_
   7
   8 #include <string>
   9
  10 #include "base/base_export.h"
  11 #include "base/base_paths.h"
  12 #include "base/gtest_prod_util.h"
  13 #include "build/build_config.h"
  14
  15 class FilePath;
  16
  17 namespace base {
  18 class ScopedPathOverride;
  19 }  // namespace
  20
  21 // The path service is a global table mapping keys to file system paths.  It is
  22 // OK to use this service from multiple threads.
  23 //
  24 class BASE_EXPORT PathService {
  25  public:
  26   // Retrieves a path to a special directory or file and places it into the
  27   // string pointed to by 'path'. If you ask for a directory it is guaranteed
  28   // to NOT have a path separator at the end. For example, "c:\windows\temp"
  29   // Directories are also guaranteed to exist when this function succeeds.
  30   //
  31   // Returns true if the directory or file was successfully retrieved. On
  32   // failure, 'path' will not be changed.
  33   static bool Get(int key, FilePath* path);
  34
  35   // Overrides the path to a special directory or file.  This cannot be used to
  36   // change the value of DIR_CURRENT, but that should be obvious.  Also, if the
  37   // path specifies a directory that does not exist, the directory will be
  38   // created by this method.  This method returns true if successful.
  39   //
  40   // If the given path is relative, then it will be resolved against
  41   // DIR_CURRENT.
  42   //
  43   // WARNING: Consumers of PathService::Get may expect paths to be constant
  44   // over the lifetime of the app, so this method should be used with caution.
  45   static bool Override(int key, const FilePath& path);
  46
  47   // This function does the same as PathService::Override but it takes an extra
  48   // parameter |create| which guides whether the directory to be overriden must
  49   // be created in case it doesn't exist already.
  50   static bool OverrideAndCreateIfNeeded(int key,
  51                                         const FilePath& path,
  52                                         bool create);
  53
  54   // To extend the set of supported keys, you can register a path provider,
  55   // which is just a function mirroring PathService::Get.  The ProviderFunc
  56   // returns false if it cannot provide a non-empty path for the given key.
  57   // Otherwise, true is returned.
  58   //
  59   // WARNING: This function could be called on any thread from which the
  60   // PathService is used, so a the ProviderFunc MUST BE THREADSAFE.
  61   //
  62   typedef bool (*ProviderFunc)(int, FilePath*);
  63
  64   // Call to register a path provider.  You must specify the range "[key_start,
  65   // key_end)" of supported path keys.
  66   static void RegisterProvider(ProviderFunc provider,
  67                                int key_start,
  68                                int key_end);
  69
  70  private:
  71   friend class base::ScopedPathOverride;
  72   FRIEND_TEST_ALL_PREFIXES(PathServiceTest, RemoveOverride);
  73
  74   // Removes an override for a special directory or file. Returns true if there
  75   // was an override to remove or false if none was present.
  76   // NOTE: This function is intended to be used by tests only!
  77   static bool RemoveOverride(int key);
  78 };
  79
  80 #endif  // BASE_PATH_SERVICE_H_