summaryrefslogtreecommitdiff
path: root/chromium/base/path_service.cc
blob: 89e58b2cdb1526169cd1e650c24dc35ccd9fb3a5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/path_service.h"

#if defined(OS_WIN)
#include <windows.h>
#include <shellapi.h>
#include <shlobj.h>
#endif

#include "base/containers/hash_tables.h"
#include "base/file_util.h"
#include "base/files/file_path.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/synchronization/lock.h"

using base::FilePath;
using base::MakeAbsoluteFilePath;

namespace base {
  bool PathProvider(int key, FilePath* result);
#if defined(OS_WIN)
  bool PathProviderWin(int key, FilePath* result);
#elif defined(OS_MACOSX)
  bool PathProviderMac(int key, FilePath* result);
#elif defined(OS_ANDROID)
  bool PathProviderAndroid(int key, FilePath* result);
#elif defined(OS_POSIX)
  // PathProviderPosix is the default path provider on POSIX OSes other than
  // Mac and Android.
  bool PathProviderPosix(int key, FilePath* result);
#endif
}

namespace {

typedef base::hash_map<int, FilePath> PathMap;

// We keep a linked list of providers.  In a debug build we ensure that no two
// providers claim overlapping keys.
struct Provider {
  PathService::ProviderFunc func;
  struct Provider* next;
#ifndef NDEBUG
  int key_start;
  int key_end;
#endif
  bool is_static;
};

Provider base_provider = {
  base::PathProvider,
  NULL,
#ifndef NDEBUG
  base::PATH_START,
  base::PATH_END,
#endif
  true
};

#if defined(OS_WIN)
Provider base_provider_win = {
  base::PathProviderWin,
  &base_provider,
#ifndef NDEBUG
  base::PATH_WIN_START,
  base::PATH_WIN_END,
#endif
  true
};
#endif

#if defined(OS_MACOSX)
Provider base_provider_mac = {
  base::PathProviderMac,
  &base_provider,
#ifndef NDEBUG
  base::PATH_MAC_START,
  base::PATH_MAC_END,
#endif
  true
};
#endif

#if defined(OS_ANDROID)
Provider base_provider_android = {
  base::PathProviderAndroid,
  &base_provider,
#ifndef NDEBUG
  base::PATH_ANDROID_START,
  base::PATH_ANDROID_END,
#endif
  true
};
#endif

#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
Provider base_provider_posix = {
  base::PathProviderPosix,
  &base_provider,
#ifndef NDEBUG
  base::PATH_POSIX_START,
  base::PATH_POSIX_END,
#endif
  true
};
#endif


struct PathData {
  base::Lock lock;
  PathMap cache;        // Cache mappings from path key to path value.
  PathMap overrides;    // Track path overrides.
  Provider* providers;  // Linked list of path service providers.
  bool cache_disabled;  // Don't use cache if true;

  PathData() : cache_disabled(false) {
#if defined(OS_WIN)
    providers = &base_provider_win;
#elif defined(OS_MACOSX)
    providers = &base_provider_mac;
#elif defined(OS_ANDROID)
    providers = &base_provider_android;
#elif defined(OS_POSIX)
    providers = &base_provider_posix;
#endif
  }

  ~PathData() {
    Provider* p = providers;
    while (p) {
      Provider* next = p->next;
      if (!p->is_static)
        delete p;
      p = next;
    }
  }
};

static base::LazyInstance<PathData> g_path_data = LAZY_INSTANCE_INITIALIZER;

static PathData* GetPathData() {
  return g_path_data.Pointer();
}

// Tries to find |key| in the cache. |path_data| should be locked by the caller!
bool LockedGetFromCache(int key, const PathData* path_data, FilePath* result) {
  if (path_data->cache_disabled)
    return false;
  // check for a cached version
  PathMap::const_iterator it = path_data->cache.find(key);
  if (it != path_data->cache.end()) {
    *result = it->second;
    return true;
  }
  return false;
}

// Tries to find |key| in the overrides map. |path_data| should be locked by the
// caller!
bool LockedGetFromOverrides(int key, PathData* path_data, FilePath* result) {
  // check for an overridden version.
  PathMap::const_iterator it = path_data->overrides.find(key);
  if (it != path_data->overrides.end()) {
    if (!path_data->cache_disabled)
      path_data->cache[key] = it->second;
    *result = it->second;
    return true;
  }
  return false;
}

}  // namespace

// TODO(brettw): this function does not handle long paths (filename > MAX_PATH)
// characters). This isn't supported very well by Windows right now, so it is
// moot, but we should keep this in mind for the future.
// static
bool PathService::Get(int key, FilePath* result) {
  PathData* path_data = GetPathData();
  DCHECK(path_data);
  DCHECK(result);
  DCHECK_GE(key, base::DIR_CURRENT);

  // special case the current directory because it can never be cached
  if (key == base::DIR_CURRENT)
    return file_util::GetCurrentDirectory(result);

  Provider* provider = NULL;
  {
    base::AutoLock scoped_lock(path_data->lock);
    if (LockedGetFromCache(key, path_data, result))
      return true;

    if (LockedGetFromOverrides(key, path_data, result))
      return true;

    // Get the beginning of the list while it is still locked.
    provider = path_data->providers;
  }

  FilePath path;

  // Iterating does not need the lock because only the list head might be
  // modified on another thread.
  while (provider) {
    if (provider->func(key, &path))
      break;
    DCHECK(path.empty()) << "provider should not have modified path";
    provider = provider->next;
  }

  if (path.empty())
    return false;

  if (path.ReferencesParent()) {
    // Make sure path service never returns a path with ".." in it.
    path = MakeAbsoluteFilePath(path);
    if (path.empty())
      return false;
  }
  *result = path;

  base::AutoLock scoped_lock(path_data->lock);
  if (!path_data->cache_disabled)
    path_data->cache[key] = path;

  return true;
}

// static
bool PathService::Override(int key, const FilePath& path) {
  // Just call the full function with true for the value of |create|.
  return OverrideAndCreateIfNeeded(key, path, true);
}

// static
bool PathService::OverrideAndCreateIfNeeded(int key,
                                            const FilePath& path,
                                            bool create) {
  PathData* path_data = GetPathData();
  DCHECK(path_data);
  DCHECK_GT(key, base::DIR_CURRENT) << "invalid path key";

  FilePath file_path = path;

  // For some locations this will fail if called from inside the sandbox there-
  // fore we protect this call with a flag.
  if (create) {
    // Make sure the directory exists. We need to do this before we translate
    // this to the absolute path because on POSIX, MakeAbsoluteFilePath fails
    // if called on a non-existent path.
    if (!base::PathExists(file_path) &&
        !file_util::CreateDirectory(file_path))
      return false;
  }

  // We need to have an absolute path.
  file_path = MakeAbsoluteFilePath(file_path);
  if (file_path.empty())
    return false;

  base::AutoLock scoped_lock(path_data->lock);

  // Clear the cache now. Some of its entries could have depended
  // on the value we are overriding, and are now out of sync with reality.
  path_data->cache.clear();

  path_data->overrides[key] = file_path;

  return true;
}

// static
bool PathService::RemoveOverride(int key) {
  PathData* path_data = GetPathData();
  DCHECK(path_data);

  base::AutoLock scoped_lock(path_data->lock);

  if (path_data->overrides.find(key) == path_data->overrides.end())
    return false;

  // Clear the cache now. Some of its entries could have depended on the value
  // we are going to remove, and are now out of sync.
  path_data->cache.clear();

  path_data->overrides.erase(key);

  return true;
}

// static
void PathService::RegisterProvider(ProviderFunc func, int key_start,
                                   int key_end) {
  PathData* path_data = GetPathData();
  DCHECK(path_data);
  DCHECK_GT(key_end, key_start);

  Provider* p;

  p = new Provider;
  p->is_static = false;
  p->func = func;
#ifndef NDEBUG
  p->key_start = key_start;
  p->key_end = key_end;
#endif

  base::AutoLock scoped_lock(path_data->lock);

#ifndef NDEBUG
  Provider *iter = path_data->providers;
  while (iter) {
    DCHECK(key_start >= iter->key_end || key_end <= iter->key_start) <<
      "path provider collision";
    iter = iter->next;
  }
#endif

  p->next = path_data->providers;
  path_data->providers = p;
}

// static
void PathService::DisableCache() {
  PathData* path_data = GetPathData();
  DCHECK(path_data);

  base::AutoLock scoped_lock(path_data->lock);
  path_data->cache.clear();
  path_data->cache_disabled = true;
}