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/sequenced_task_runner.h"
17#include "base/threading/sequenced_worker_pool.h"
18#include "base/values.h"
19
20namespace {
21
22// Some extensions we'll tack on to copies of the Preferences files.
23const base::FilePath::CharType* kBadExtension = FILE_PATH_LITERAL("bad");
24
25// Differentiates file loading between origin thread and passed
26// (aka file) thread.
27class FileThreadDeserializer
28    : public base::RefCountedThreadSafe<FileThreadDeserializer> {
29 public:
30  FileThreadDeserializer(JsonPrefStore* delegate,
31                         base::SequencedTaskRunner* sequenced_task_runner)
32      : no_dir_(false),
33        error_(PersistentPrefStore::PREF_READ_ERROR_NONE),
34        delegate_(delegate),
35        sequenced_task_runner_(sequenced_task_runner),
36        origin_loop_proxy_(base::MessageLoopProxy::current()) {
37  }
38
39  void Start(const base::FilePath& path) {
40    DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
41    sequenced_task_runner_->PostTask(
42        FROM_HERE,
43        base::Bind(&FileThreadDeserializer::ReadFileAndReport,
44                   this, path));
45  }
46
47  // Deserializes JSON on the sequenced task runner.
48  void ReadFileAndReport(const base::FilePath& path) {
49    DCHECK(sequenced_task_runner_->RunsTasksOnCurrentThread());
50
51    value_.reset(DoReading(path, &error_, &no_dir_));
52
53    origin_loop_proxy_->PostTask(
54        FROM_HERE,
55        base::Bind(&FileThreadDeserializer::ReportOnOriginThread, this));
56  }
57
58  // Reports deserialization result on the origin thread.
59  void ReportOnOriginThread() {
60    DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
61    delegate_->OnFileRead(value_.release(), error_, no_dir_);
62  }
63
64  static base::Value* DoReading(const base::FilePath& path,
65                                PersistentPrefStore::PrefReadError* error,
66                                bool* no_dir) {
67    int error_code;
68    std::string error_msg;
69    JSONFileValueSerializer serializer(path);
70    base::Value* value = serializer.Deserialize(&error_code, &error_msg);
71    HandleErrors(value, path, error_code, error_msg, error);
72    *no_dir = !base::PathExists(path.DirName());
73    return value;
74  }
75
76  static void HandleErrors(const base::Value* value,
77                           const base::FilePath& path,
78                           int error_code,
79                           const std::string& error_msg,
80                           PersistentPrefStore::PrefReadError* error);
81
82 private:
83  friend class base::RefCountedThreadSafe<FileThreadDeserializer>;
84  ~FileThreadDeserializer() {}
85
86  bool no_dir_;
87  PersistentPrefStore::PrefReadError error_;
88  scoped_ptr<base::Value> value_;
89  const scoped_refptr<JsonPrefStore> delegate_;
90  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
91  const scoped_refptr<base::MessageLoopProxy> origin_loop_proxy_;
92};
93
94// static
95void FileThreadDeserializer::HandleErrors(
96    const base::Value* value,
97    const base::FilePath& path,
98    int error_code,
99    const std::string& error_msg,
100    PersistentPrefStore::PrefReadError* error) {
101  *error = PersistentPrefStore::PREF_READ_ERROR_NONE;
102  if (!value) {
103    DVLOG(1) << "Error while loading JSON file: " << error_msg
104             << ", file: " << path.value();
105    switch (error_code) {
106      case JSONFileValueSerializer::JSON_ACCESS_DENIED:
107        *error = PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
108        break;
109      case JSONFileValueSerializer::JSON_CANNOT_READ_FILE:
110        *error = PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
111        break;
112      case JSONFileValueSerializer::JSON_FILE_LOCKED:
113        *error = PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
114        break;
115      case JSONFileValueSerializer::JSON_NO_SUCH_FILE:
116        *error = PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
117        break;
118      default:
119        *error = PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
120        // JSON errors indicate file corruption of some sort.
121        // Since the file is corrupt, move it to the side and continue with
122        // empty preferences.  This will result in them losing their settings.
123        // We keep the old file for possible support and debugging assistance
124        // as well as to detect if they're seeing these errors repeatedly.
125        // TODO(erikkay) Instead, use the last known good file.
126        base::FilePath bad = path.ReplaceExtension(kBadExtension);
127
128        // If they've ever had a parse error before, put them in another bucket.
129        // TODO(erikkay) if we keep this error checking for very long, we may
130        // want to differentiate between recent and long ago errors.
131        if (base::PathExists(bad))
132          *error = PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT;
133        base::Move(path, bad);
134        break;
135    }
136  } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
137    *error = PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
138  }
139}
140
141}  // namespace
142
143scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
144    const base::FilePath& filename,
145    base::SequencedWorkerPool* worker_pool) {
146  std::string token("json_pref_store-");
147  token.append(filename.AsUTF8Unsafe());
148  return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
149      worker_pool->GetNamedSequenceToken(token),
150      base::SequencedWorkerPool::BLOCK_SHUTDOWN);
151}
152
153JsonPrefStore::JsonPrefStore(const base::FilePath& filename,
154                             base::SequencedTaskRunner* sequenced_task_runner)
155    : path_(filename),
156      sequenced_task_runner_(sequenced_task_runner),
157      prefs_(new base::DictionaryValue()),
158      read_only_(false),
159      writer_(filename, sequenced_task_runner),
160      initialized_(false),
161      read_error_(PREF_READ_ERROR_OTHER) {}
162
163bool JsonPrefStore::GetValue(const std::string& key,
164                             const base::Value** result) const {
165  base::Value* tmp = NULL;
166  if (!prefs_->Get(key, &tmp))
167    return false;
168
169  if (result)
170    *result = tmp;
171  return true;
172}
173
174void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
175  observers_.AddObserver(observer);
176}
177
178void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
179  observers_.RemoveObserver(observer);
180}
181
182bool JsonPrefStore::HasObservers() const {
183  return observers_.might_have_observers();
184}
185
186bool JsonPrefStore::IsInitializationComplete() const {
187  return initialized_;
188}
189
190bool JsonPrefStore::GetMutableValue(const std::string& key,
191                                    base::Value** result) {
192  return prefs_->Get(key, result);
193}
194
195void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
196  DCHECK(value);
197  scoped_ptr<base::Value> new_value(value);
198  base::Value* old_value = NULL;
199  prefs_->Get(key, &old_value);
200  if (!old_value || !value->Equals(old_value)) {
201    prefs_->Set(key, new_value.release());
202    ReportValueChanged(key);
203  }
204}
205
206void JsonPrefStore::SetValueSilently(const std::string& key,
207                                     base::Value* value) {
208  DCHECK(value);
209  scoped_ptr<base::Value> new_value(value);
210  base::Value* old_value = NULL;
211  prefs_->Get(key, &old_value);
212  if (!old_value || !value->Equals(old_value)) {
213    prefs_->Set(key, new_value.release());
214    if (!read_only_)
215      writer_.ScheduleWrite(this);
216  }
217}
218
219void JsonPrefStore::RemoveValue(const std::string& key) {
220  if (prefs_->RemovePath(key, NULL))
221    ReportValueChanged(key);
222}
223
224bool JsonPrefStore::ReadOnly() const {
225  return read_only_;
226}
227
228PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
229  return read_error_;
230}
231
232PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
233  if (path_.empty()) {
234    OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
235    return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
236  }
237
238  PrefReadError error;
239  bool no_dir;
240  base::Value* value =
241      FileThreadDeserializer::DoReading(path_, &error, &no_dir);
242  OnFileRead(value, error, no_dir);
243  return error;
244}
245
246void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate *error_delegate) {
247  initialized_ = false;
248  error_delegate_.reset(error_delegate);
249  if (path_.empty()) {
250    OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
251    return;
252  }
253
254  // Start async reading of the preferences file. It will delete itself
255  // in the end.
256  scoped_refptr<FileThreadDeserializer> deserializer(
257      new FileThreadDeserializer(this, sequenced_task_runner_.get()));
258  deserializer->Start(path_);
259}
260
261void JsonPrefStore::CommitPendingWrite() {
262  if (writer_.HasPendingWrite() && !read_only_)
263    writer_.DoScheduledWrite();
264}
265
266void JsonPrefStore::ReportValueChanged(const std::string& key) {
267  FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
268  if (!read_only_)
269    writer_.ScheduleWrite(this);
270}
271
272void JsonPrefStore::OnFileRead(base::Value* value_owned,
273                               PersistentPrefStore::PrefReadError error,
274                               bool no_dir) {
275  scoped_ptr<base::Value> value(value_owned);
276  read_error_ = error;
277
278  if (no_dir) {
279    FOR_EACH_OBSERVER(PrefStore::Observer,
280                      observers_,
281                      OnInitializationCompleted(false));
282    return;
283  }
284
285  initialized_ = true;
286
287  switch (error) {
288    case PREF_READ_ERROR_ACCESS_DENIED:
289    case PREF_READ_ERROR_FILE_OTHER:
290    case PREF_READ_ERROR_FILE_LOCKED:
291    case PREF_READ_ERROR_JSON_TYPE:
292    case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
293      read_only_ = true;
294      break;
295    case PREF_READ_ERROR_NONE:
296      DCHECK(value.get());
297      prefs_.reset(static_cast<base::DictionaryValue*>(value.release()));
298      break;
299    case PREF_READ_ERROR_NO_FILE:
300      // If the file just doesn't exist, maybe this is first run.  In any case
301      // there's no harm in writing out default prefs in this case.
302      break;
303    case PREF_READ_ERROR_JSON_PARSE:
304    case PREF_READ_ERROR_JSON_REPEAT:
305      break;
306    default:
307      NOTREACHED() << "Unknown error: " << error;
308  }
309
310  if (error_delegate_.get() && error != PREF_READ_ERROR_NONE)
311    error_delegate_->OnError(error);
312
313  FOR_EACH_OBSERVER(PrefStore::Observer,
314                    observers_,
315                    OnInitializationCompleted(true));
316}
317
318JsonPrefStore::~JsonPrefStore() {
319  CommitPendingWrite();
320}
321
322bool JsonPrefStore::SerializeData(std::string* output) {
323  JSONStringValueSerializer serializer(output);
324  serializer.set_pretty_print(true);
325  return serializer.Serialize(*prefs_);
326}
327