path_service.h revision 3345a6884c488ff3a535c2c9acdd33d74b37e311 
1// Copyright (c) 2006-2008 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#pragma once
8
9#include "build/build_config.h"
10
11#include <string>
12
13#include "base/base_paths.h"
14
15class FilePath;
16
17// The path service is a global table mapping keys to file system paths.  It is
18// OK to use this service from multiple threads.
19//
20class PathService {
21 public:
22  // Retrieves a path to a special directory or file and places it into the
23  // string pointed to by 'path'. If you ask for a directory it is guaranteed
24  // to NOT have a path separator at the end. For example, "c:\windows\temp"
25  // Directories are also guaranteed to exist when this function succeeds.
26  //
27  // Returns true if the directory or file was successfully retrieved. On
28  // failure, 'path' will not be changed.
29  static bool Get(int key, FilePath* path);
30#if defined(OS_WIN)
31  // This version, producing a wstring, is deprecated and only kept around
32  // until we can fix all callers.
33  static bool Get(int key, std::wstring* path);
34#endif
35
36  // Overrides the path to a special directory or file.  This cannot be used to
37  // change the value of DIR_CURRENT, but that should be obvious.  Also, if the
38  // path specifies a directory that does not exist, the directory will be
39  // created by this method.  This method returns true if successful.
40  //
41  // If the given path is relative, then it will be resolved against
42  // DIR_CURRENT.
43  //
44  // WARNING: Consumers of PathService::Get may expect paths to be constant
45  // over the lifetime of the app, so this method should be used with caution.
46  static bool Override(int key, const FilePath& path);
47
48  // To extend the set of supported keys, you can register a path provider,
49  // which is just a function mirroring PathService::Get.  The ProviderFunc
50  // returns false if it cannot provide a non-empty path for the given key.
51  // Otherwise, true is returned.
52  //
53  // WARNING: This function could be called on any thread from which the
54  // PathService is used, so a the ProviderFunc MUST BE THREADSAFE.
55  //
56  typedef bool (*ProviderFunc)(int, FilePath*);
57
58  // Call to register a path provider.  You must specify the range "[key_start,
59  // key_end)" of supported path keys.
60  static void RegisterProvider(ProviderFunc provider,
61                               int key_start,
62                               int key_end);
63 private:
64  static bool GetFromCache(int key, FilePath* path);
65  static bool GetFromOverrides(int key, FilePath* path);
66  static void AddToCache(int key, const FilePath& path);
67};
68
69#endif  // BASE_PATH_SERVICE_H_
70