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/prefs/json_pref_store.h"
6
7#include <algorithm>
8
9#include "base/bind.h"
10#include "base/callback.h"
11#include "base/file_util.h"
12#include "base/json/json_file_value_serializer.h"
13#include "base/json/json_string_value_serializer.h"
14#include "base/memory/ref_counted.h"
15#include "base/message_loop/message_loop_proxy.h"
16#include "base/prefs/pref_filter.h"
17#include "base/sequenced_task_runner.h"
18#include "base/threading/sequenced_worker_pool.h"
19#include "base/values.h"
20
21namespace {
22
23// Some extensions we'll tack on to copies of the Preferences files.
24const base::FilePath::CharType* kBadExtension = FILE_PATH_LITERAL("bad");
25
26// Differentiates file loading between origin thread and passed
27// (aka file) thread.
28class FileThreadDeserializer
29    : public base::RefCountedThreadSafe<FileThreadDeserializer> {
30 public:
31  FileThreadDeserializer(JsonPrefStore* delegate,
32                         base::SequencedTaskRunner* sequenced_task_runner)
33      : no_dir_(false),
34        error_(PersistentPrefStore::PREF_READ_ERROR_NONE),
35        delegate_(delegate),
36        sequenced_task_runner_(sequenced_task_runner),
37        origin_loop_proxy_(base::MessageLoopProxy::current()) {
38  }
39
40  void Start(const base::FilePath& path,
41             const base::FilePath& alternate_path) {
42    DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
43    // TODO(gab): This should use PostTaskAndReplyWithResult instead of using
44    // the |error_| member to pass data across tasks.
45    sequenced_task_runner_->PostTask(
46        FROM_HERE,
47        base::Bind(&FileThreadDeserializer::ReadFileAndReport,
48                   this, path, alternate_path));
49  }
50
51  // Deserializes JSON on the sequenced task runner.
52  void ReadFileAndReport(const base::FilePath& path,
53                         const base::FilePath& alternate_path) {
54    DCHECK(sequenced_task_runner_->RunsTasksOnCurrentThread());
55
56    value_.reset(DoReading(path, alternate_path, &error_, &no_dir_));
57
58    origin_loop_proxy_->PostTask(
59        FROM_HERE,
60        base::Bind(&FileThreadDeserializer::ReportOnOriginThread, this));
61  }
62
63  // Reports deserialization result on the origin thread.
64  void ReportOnOriginThread() {
65    DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
66    delegate_->OnFileRead(value_.Pass(), error_, no_dir_);
67  }
68
69  static base::Value* DoReading(const base::FilePath& path,
70                                const base::FilePath& alternate_path,
71                                PersistentPrefStore::PrefReadError* error,
72                                bool* no_dir) {
73    if (!base::PathExists(path) && !alternate_path.empty() &&
74        base::PathExists(alternate_path)) {
75      base::Move(alternate_path, path);
76    }
77
78    int error_code;
79    std::string error_msg;
80    JSONFileValueSerializer serializer(path);
81    base::Value* value = serializer.Deserialize(&error_code, &error_msg);
82    HandleErrors(value, path, error_code, error_msg, error);
83    *no_dir = !base::PathExists(path.DirName());
84    return value;
85  }
86
87  static void HandleErrors(const base::Value* value,
88                           const base::FilePath& path,
89                           int error_code,
90                           const std::string& error_msg,
91                           PersistentPrefStore::PrefReadError* error);
92
93 private:
94  friend class base::RefCountedThreadSafe<FileThreadDeserializer>;
95  ~FileThreadDeserializer() {}
96
97  bool no_dir_;
98  PersistentPrefStore::PrefReadError error_;
99  scoped_ptr<base::Value> value_;
100  const scoped_refptr<JsonPrefStore> delegate_;
101  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
102  const scoped_refptr<base::MessageLoopProxy> origin_loop_proxy_;
103};
104
105// static
106void FileThreadDeserializer::HandleErrors(
107    const base::Value* value,
108    const base::FilePath& path,
109    int error_code,
110    const std::string& error_msg,
111    PersistentPrefStore::PrefReadError* error) {
112  *error = PersistentPrefStore::PREF_READ_ERROR_NONE;
113  if (!value) {
114    DVLOG(1) << "Error while loading JSON file: " << error_msg
115             << ", file: " << path.value();
116    switch (error_code) {
117      case JSONFileValueSerializer::JSON_ACCESS_DENIED:
118        *error = PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
119        break;
120      case JSONFileValueSerializer::JSON_CANNOT_READ_FILE:
121        *error = PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
122        break;
123      case JSONFileValueSerializer::JSON_FILE_LOCKED:
124        *error = PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
125        break;
126      case JSONFileValueSerializer::JSON_NO_SUCH_FILE:
127        *error = PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
128        break;
129      default:
130        *error = PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
131        // JSON errors indicate file corruption of some sort.
132        // Since the file is corrupt, move it to the side and continue with
133        // empty preferences.  This will result in them losing their settings.
134        // We keep the old file for possible support and debugging assistance
135        // as well as to detect if they're seeing these errors repeatedly.
136        // TODO(erikkay) Instead, use the last known good file.
137        base::FilePath bad = path.ReplaceExtension(kBadExtension);
138
139        // If they've ever had a parse error before, put them in another bucket.
140        // TODO(erikkay) if we keep this error checking for very long, we may
141        // want to differentiate between recent and long ago errors.
142        if (base::PathExists(bad))
143          *error = PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT;
144        base::Move(path, bad);
145        break;
146    }
147  } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
148    *error = PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
149  }
150}
151
152}  // namespace
153
154scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
155    const base::FilePath& filename,
156    base::SequencedWorkerPool* worker_pool) {
157  std::string token("json_pref_store-");
158  token.append(filename.AsUTF8Unsafe());
159  return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
160      worker_pool->GetNamedSequenceToken(token),
161      base::SequencedWorkerPool::BLOCK_SHUTDOWN);
162}
163
164JsonPrefStore::JsonPrefStore(const base::FilePath& filename,
165                             base::SequencedTaskRunner* sequenced_task_runner,
166                             scoped_ptr<PrefFilter> pref_filter)
167    : path_(filename),
168      sequenced_task_runner_(sequenced_task_runner),
169      prefs_(new base::DictionaryValue()),
170      read_only_(false),
171      writer_(filename, sequenced_task_runner),
172      pref_filter_(pref_filter.Pass()),
173      initialized_(false),
174      filtering_in_progress_(false),
175      read_error_(PREF_READ_ERROR_NONE) {
176}
177
178JsonPrefStore::JsonPrefStore(const base::FilePath& filename,
179                             const base::FilePath& alternate_filename,
180                             base::SequencedTaskRunner* sequenced_task_runner,
181                             scoped_ptr<PrefFilter> pref_filter)
182    : path_(filename),
183      alternate_path_(alternate_filename),
184      sequenced_task_runner_(sequenced_task_runner),
185      prefs_(new base::DictionaryValue()),
186      read_only_(false),
187      writer_(filename, sequenced_task_runner),
188      pref_filter_(pref_filter.Pass()),
189      initialized_(false),
190      filtering_in_progress_(false),
191      read_error_(PREF_READ_ERROR_NONE) {
192}
193
194bool JsonPrefStore::GetValue(const std::string& key,
195                             const base::Value** result) const {
196  base::Value* tmp = NULL;
197  if (!prefs_->Get(key, &tmp))
198    return false;
199
200  if (result)
201    *result = tmp;
202  return true;
203}
204
205void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
206  observers_.AddObserver(observer);
207}
208
209void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
210  observers_.RemoveObserver(observer);
211}
212
213bool JsonPrefStore::HasObservers() const {
214  return observers_.might_have_observers();
215}
216
217bool JsonPrefStore::IsInitializationComplete() const {
218  return initialized_;
219}
220
221bool JsonPrefStore::GetMutableValue(const std::string& key,
222                                    base::Value** result) {
223  return prefs_->Get(key, result);
224}
225
226void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
227  DCHECK(value);
228  scoped_ptr<base::Value> new_value(value);
229  base::Value* old_value = NULL;
230  prefs_->Get(key, &old_value);
231  if (!old_value || !value->Equals(old_value)) {
232    prefs_->Set(key, new_value.release());
233    ReportValueChanged(key);
234  }
235}
236
237void JsonPrefStore::SetValueSilently(const std::string& key,
238                                     base::Value* value) {
239  DCHECK(value);
240  scoped_ptr<base::Value> new_value(value);
241  base::Value* old_value = NULL;
242  prefs_->Get(key, &old_value);
243  if (!old_value || !value->Equals(old_value)) {
244    prefs_->Set(key, new_value.release());
245    if (!read_only_)
246      writer_.ScheduleWrite(this);
247  }
248}
249
250void JsonPrefStore::RemoveValue(const std::string& key) {
251  if (prefs_->RemovePath(key, NULL))
252    ReportValueChanged(key);
253}
254
255void JsonPrefStore::RemoveValueSilently(const std::string& key) {
256  prefs_->RemovePath(key, NULL);
257  if (!read_only_)
258    writer_.ScheduleWrite(this);
259}
260
261bool JsonPrefStore::ReadOnly() const {
262  return read_only_;
263}
264
265PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
266  return read_error_;
267}
268
269PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
270  if (path_.empty()) {
271    OnFileRead(
272        scoped_ptr<base::Value>(), PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
273    return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
274  }
275
276  PrefReadError error;
277  bool no_dir;
278  scoped_ptr<base::Value> value(
279      FileThreadDeserializer::DoReading(path_, alternate_path_, &error,
280                                        &no_dir));
281  OnFileRead(value.Pass(), error, no_dir);
282  return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE :
283                                  error;
284}
285
286void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
287  initialized_ = false;
288  error_delegate_.reset(error_delegate);
289  if (path_.empty()) {
290    OnFileRead(
291        scoped_ptr<base::Value>(), PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
292    return;
293  }
294
295  // Start async reading of the preferences file. It will delete itself
296  // in the end.
297  scoped_refptr<FileThreadDeserializer> deserializer(
298      new FileThreadDeserializer(this, sequenced_task_runner_.get()));
299  deserializer->Start(path_, alternate_path_);
300}
301
302void JsonPrefStore::CommitPendingWrite() {
303  if (writer_.HasPendingWrite() && !read_only_)
304    writer_.DoScheduledWrite();
305}
306
307void JsonPrefStore::ReportValueChanged(const std::string& key) {
308  if (pref_filter_)
309    pref_filter_->FilterUpdate(key);
310
311  FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
312
313  if (!read_only_)
314    writer_.ScheduleWrite(this);
315}
316
317void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
318    const base::Closure& on_next_successful_write) {
319  writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
320}
321
322void JsonPrefStore::OnFileRead(scoped_ptr<base::Value> value,
323                               PersistentPrefStore::PrefReadError error,
324                               bool no_dir) {
325  scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
326
327  read_error_ = error;
328
329  bool initialization_successful = !no_dir;
330
331  if (initialization_successful) {
332    switch (read_error_) {
333      case PREF_READ_ERROR_ACCESS_DENIED:
334      case PREF_READ_ERROR_FILE_OTHER:
335      case PREF_READ_ERROR_FILE_LOCKED:
336      case PREF_READ_ERROR_JSON_TYPE:
337      case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
338        read_only_ = true;
339        break;
340      case PREF_READ_ERROR_NONE:
341        DCHECK(value.get());
342        unfiltered_prefs.reset(
343            static_cast<base::DictionaryValue*>(value.release()));
344        break;
345      case PREF_READ_ERROR_NO_FILE:
346        // If the file just doesn't exist, maybe this is first run.  In any case
347        // there's no harm in writing out default prefs in this case.
348        break;
349      case PREF_READ_ERROR_JSON_PARSE:
350      case PREF_READ_ERROR_JSON_REPEAT:
351        break;
352      case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
353        // This is a special error code to be returned by ReadPrefs when it
354        // can't complete synchronously, it should never be returned by the read
355        // operation itself.
356        NOTREACHED();
357        break;
358      case PREF_READ_ERROR_LEVELDB_IO:
359      case PREF_READ_ERROR_LEVELDB_CORRUPTION_READ_ONLY:
360      case PREF_READ_ERROR_LEVELDB_CORRUPTION:
361        // These are specific to LevelDBPrefStore.
362        NOTREACHED();
363      case PREF_READ_ERROR_MAX_ENUM:
364        NOTREACHED();
365        break;
366    }
367  }
368
369  if (pref_filter_) {
370    filtering_in_progress_ = true;
371    const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
372        base::Bind(
373            &JsonPrefStore::FinalizeFileRead, this, initialization_successful));
374    pref_filter_->FilterOnLoad(post_filter_on_load_callback,
375                               unfiltered_prefs.Pass());
376  } else {
377    FinalizeFileRead(initialization_successful, unfiltered_prefs.Pass(), false);
378  }
379}
380
381JsonPrefStore::~JsonPrefStore() {
382  CommitPendingWrite();
383}
384
385bool JsonPrefStore::SerializeData(std::string* output) {
386  if (pref_filter_)
387    pref_filter_->FilterSerializeData(prefs_.get());
388
389  JSONStringValueSerializer serializer(output);
390  serializer.set_pretty_print(true);
391  return serializer.Serialize(*prefs_);
392}
393
394void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
395                                     scoped_ptr<base::DictionaryValue> prefs,
396                                     bool schedule_write) {
397  filtering_in_progress_ = false;
398
399  if (!initialization_successful) {
400    FOR_EACH_OBSERVER(PrefStore::Observer,
401                      observers_,
402                      OnInitializationCompleted(false));
403    return;
404  }
405
406  prefs_ = prefs.Pass();
407
408  initialized_ = true;
409
410  if (schedule_write && !read_only_)
411    writer_.ScheduleWrite(this);
412
413  if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
414    error_delegate_->OnError(read_error_);
415
416  FOR_EACH_OBSERVER(PrefStore::Observer,
417                    observers_,
418                    OnInitializationCompleted(true));
419
420  return;
421}
422