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 namespace base {
  16 class FilePath;
  17 class ScopedPathOverride;
  18 }  // namespace
  19
  20 // The path service is a global table mapping keys to file system paths.  It is
  21 // OK to use this service from multiple threads.
  22 //
  23 class BASE_EXPORT PathService {
  24  public:
  25   // Retrieves a path to a special directory or file and places it into the
  26   // string pointed to by 'path'. If you ask for a directory it is guaranteed
  27   // to NOT have a path separator at the end. For example, "c:\windows\temp"
  28   // Directories are also guaranteed to exist when this function succeeds.
  29   //
  30   // Returns true if the directory or file was successfully retrieved. On
  31   // failure, 'path' will not be changed.
  32   static bool Get(int key, base::FilePath* path);
  33
  34   // Overrides the path to a special directory or file.  This cannot be used to
  35   // change the value of DIR_CURRENT, but that should be obvious.  Also, if the
  36   // path specifies a directory that does not exist, the directory will be
  37   // created by this method.  This method returns true if successful.
  38   //
  39   // If the given path is relative, then it will be resolved against
  40   // DIR_CURRENT.
  41   //
  42   // WARNING: Consumers of PathService::Get may expect paths to be constant
  43   // over the lifetime of the app, so this method should be used with caution.
  44   //
  45   // Unit tests generally should use ScopedPathOverride instead. Overrides from
  46   // one test should not carry over to another.
  47   static bool Override(int key, const base::FilePath& path);
  48
  49   // This function does the same as PathService::Override but it takes extra
  50   // parameters:
  51   // - |is_absolute| indicates that |path| has already been expanded into an
  52   // absolute path, otherwise MakeAbsoluteFilePath() will be used. This is
  53   // useful to override paths that may not exist yet, since MakeAbsoluteFilePath
  54   // fails for those. Note that MakeAbsoluteFilePath also expands symbolic
  55   // links, even if path.IsAbsolute() is already true.
  56   // - |create| guides whether the directory to be overriden must
  57   // be created in case it doesn't exist already.
  58   static bool OverrideAndCreateIfNeeded(int key,
  59                                         const base::FilePath& path,
  60                                         bool is_absolute,
  61                                         bool create);
  62
  63   // To extend the set of supported keys, you can register a path provider,
  64   // which is just a function mirroring PathService::Get.  The ProviderFunc
  65   // returns false if it cannot provide a non-empty path for the given key.
  66   // Otherwise, true is returned.
  67   //
  68   // WARNING: This function could be called on any thread from which the
  69   // PathService is used, so a the ProviderFunc MUST BE THREADSAFE.
  70   //
  71   typedef bool (*ProviderFunc)(int, base::FilePath*);
  72
  73   // Call to register a path provider.  You must specify the range "[key_start,
  74   // key_end)" of supported path keys.
  75   static void RegisterProvider(ProviderFunc provider,
  76                                int key_start,
  77                                int key_end);
  78
  79   // Disable internal cache.
  80   static void DisableCache();
  81
  82  private:
  83   friend class base::ScopedPathOverride;
  84   FRIEND_TEST_ALL_PREFIXES(PathServiceTest, RemoveOverride);
  85
  86   // Removes an override for a special directory or file. Returns true if there
  87   // was an override to remove or false if none was present.
  88   // NOTE: This function is intended to be used by tests only!
  89   static bool RemoveOverride(int key);
  90 };
  91
  92 #endif  // BASE_PATH_SERVICE_H_