base/prefs/json_pref_store.cc

   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
  21 namespace {
  22
  23 // Some extensions we'll tack on to copies of the Preferences files.
  24 const base::FilePath::CharType* kBadExtension = FILE_PATH_LITERAL("bad");
  25
  26 // Differentiates file loading between origin thread and passed
  27 // (aka file) thread.
  28 class 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     DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
  42     sequenced_task_runner_->PostTask(
  43         FROM_HERE,
  44         base::Bind(&FileThreadDeserializer::ReadFileAndReport,
  45                    this, path));
  46   }
  47
  48   // Deserializes JSON on the sequenced task runner.
  49   void ReadFileAndReport(const base::FilePath& path) {
  50     DCHECK(sequenced_task_runner_->RunsTasksOnCurrentThread());
  51
  52     value_.reset(DoReading(path, &error_, &no_dir_));
  53
  54     origin_loop_proxy_->PostTask(
  55         FROM_HERE,
  56         base::Bind(&FileThreadDeserializer::ReportOnOriginThread, this));
  57   }
  58
  59   // Reports deserialization result on the origin thread.
  60   void ReportOnOriginThread() {
  61     DCHECK(origin_loop_proxy_->BelongsToCurrentThread());
  62     delegate_->OnFileRead(value_.release(), error_, no_dir_);
  63   }
  64
  65   static base::Value* DoReading(const base::FilePath& path,
  66                                 PersistentPrefStore::PrefReadError* error,
  67                                 bool* no_dir) {
  68     int error_code;
  69     std::string error_msg;
  70     JSONFileValueSerializer serializer(path);
  71     base::Value* value = serializer.Deserialize(&error_code, &error_msg);
  72     HandleErrors(value, path, error_code, error_msg, error);
  73     *no_dir = !base::PathExists(path.DirName());
  74     return value;
  75   }
  76
  77   static void HandleErrors(const base::Value* value,
  78                            const base::FilePath& path,
  79                            int error_code,
  80                            const std::string& error_msg,
  81                            PersistentPrefStore::PrefReadError* error);
  82
  83  private:
  84   friend class base::RefCountedThreadSafe<FileThreadDeserializer>;
  85   ~FileThreadDeserializer() {}
  86
  87   bool no_dir_;
  88   PersistentPrefStore::PrefReadError error_;
  89   scoped_ptr<base::Value> value_;
  90   const scoped_refptr<JsonPrefStore> delegate_;
  91   const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
  92   const scoped_refptr<base::MessageLoopProxy> origin_loop_proxy_;
  93 };
  94
  95 // static
  96 void FileThreadDeserializer::HandleErrors(
  97     const base::Value* value,
  98     const base::FilePath& path,
  99     int error_code,
 100     const std::string& error_msg,
 101     PersistentPrefStore::PrefReadError* error) {
 102   *error = PersistentPrefStore::PREF_READ_ERROR_NONE;
 103   if (!value) {
 104     DVLOG(1) << "Error while loading JSON file: " << error_msg
 105              << ", file: " << path.value();
 106     switch (error_code) {
 107       case JSONFileValueSerializer::JSON_ACCESS_DENIED:
 108         *error = PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
 109         break;
 110       case JSONFileValueSerializer::JSON_CANNOT_READ_FILE:
 111         *error = PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
 112         break;
 113       case JSONFileValueSerializer::JSON_FILE_LOCKED:
 114         *error = PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
 115         break;
 116       case JSONFileValueSerializer::JSON_NO_SUCH_FILE:
 117         *error = PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
 118         break;
 119       default:
 120         *error = PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
 121         // JSON errors indicate file corruption of some sort.
 122         // Since the file is corrupt, move it to the side and continue with
 123         // empty preferences.  This will result in them losing their settings.
 124         // We keep the old file for possible support and debugging assistance
 125         // as well as to detect if they're seeing these errors repeatedly.
 126         // TODO(erikkay) Instead, use the last known good file.
 127         base::FilePath bad = path.ReplaceExtension(kBadExtension);
 128
 129         // If they've ever had a parse error before, put them in another bucket.
 130         // TODO(erikkay) if we keep this error checking for very long, we may
 131         // want to differentiate between recent and long ago errors.
 132         if (base::PathExists(bad))
 133           *error = PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT;
 134         base::Move(path, bad);
 135         break;
 136     }
 137   } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
 138     *error = PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
 139   }
 140 }
 141
 142 }  // namespace
 143
 144 scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
 145     const base::FilePath& filename,
 146     base::SequencedWorkerPool* worker_pool) {
 147   std::string token("json_pref_store-");
 148   token.append(filename.AsUTF8Unsafe());
 149   return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
 150       worker_pool->GetNamedSequenceToken(token),
 151       base::SequencedWorkerPool::BLOCK_SHUTDOWN);
 152 }
 153
 154 JsonPrefStore::JsonPrefStore(const base::FilePath& filename,
 155                              base::SequencedTaskRunner* sequenced_task_runner,
 156                              scoped_ptr<PrefFilter> pref_filter)
 157     : path_(filename),
 158       sequenced_task_runner_(sequenced_task_runner),
 159       prefs_(new base::DictionaryValue()),
 160       read_only_(false),
 161       writer_(filename, sequenced_task_runner),
 162       pref_filter_(pref_filter.Pass()),
 163       initialized_(false),
 164       read_error_(PREF_READ_ERROR_OTHER) {}
 165
 166 bool JsonPrefStore::GetValue(const std::string& key,
 167                              const base::Value** result) const {
 168   base::Value* tmp = NULL;
 169   if (!prefs_->Get(key, &tmp))
 170     return false;
 171
 172   if (result)
 173     *result = tmp;
 174   return true;
 175 }
 176
 177 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 178   observers_.AddObserver(observer);
 179 }
 180
 181 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 182   observers_.RemoveObserver(observer);
 183 }
 184
 185 bool JsonPrefStore::HasObservers() const {
 186   return observers_.might_have_observers();
 187 }
 188
 189 bool JsonPrefStore::IsInitializationComplete() const {
 190   return initialized_;
 191 }
 192
 193 bool JsonPrefStore::GetMutableValue(const std::string& key,
 194                                     base::Value** result) {
 195   return prefs_->Get(key, result);
 196 }
 197
 198 void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
 199   DCHECK(value);
 200   scoped_ptr<base::Value> new_value(value);
 201   base::Value* old_value = NULL;
 202   prefs_->Get(key, &old_value);
 203   if (!old_value || !value->Equals(old_value)) {
 204     prefs_->Set(key, new_value.release());
 205     ReportValueChanged(key);
 206   }
 207 }
 208
 209 void JsonPrefStore::SetValueSilently(const std::string& key,
 210                                      base::Value* value) {
 211   DCHECK(value);
 212   scoped_ptr<base::Value> new_value(value);
 213   base::Value* old_value = NULL;
 214   prefs_->Get(key, &old_value);
 215   if (!old_value || !value->Equals(old_value)) {
 216     prefs_->Set(key, new_value.release());
 217     if (!read_only_)
 218       writer_.ScheduleWrite(this);
 219   }
 220 }
 221
 222 void JsonPrefStore::RemoveValue(const std::string& key) {
 223   if (prefs_->RemovePath(key, NULL))
 224     ReportValueChanged(key);
 225 }
 226
 227 bool JsonPrefStore::ReadOnly() const {
 228   return read_only_;
 229 }
 230
 231 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 232   return read_error_;
 233 }
 234
 235 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 236   if (path_.empty()) {
 237     OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
 238     return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 239   }
 240
 241   PrefReadError error;
 242   bool no_dir;
 243   base::Value* value =
 244       FileThreadDeserializer::DoReading(path_, &error, &no_dir);
 245   OnFileRead(value, error, no_dir);
 246   return error;
 247 }
 248
 249 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate *error_delegate) {
 250   initialized_ = false;
 251   error_delegate_.reset(error_delegate);
 252   if (path_.empty()) {
 253     OnFileRead(NULL, PREF_READ_ERROR_FILE_NOT_SPECIFIED, false);
 254     return;
 255   }
 256
 257   // Start async reading of the preferences file. It will delete itself
 258   // in the end.
 259   scoped_refptr<FileThreadDeserializer> deserializer(
 260       new FileThreadDeserializer(this, sequenced_task_runner_.get()));
 261   deserializer->Start(path_);
 262 }
 263
 264 void JsonPrefStore::CommitPendingWrite() {
 265   if (writer_.HasPendingWrite() && !read_only_)
 266     writer_.DoScheduledWrite();
 267 }
 268
 269 void JsonPrefStore::ReportValueChanged(const std::string& key) {
 270   if (pref_filter_)
 271     pref_filter_->FilterUpdate(key);
 272
 273   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 274
 275   if (!read_only_)
 276     writer_.ScheduleWrite(this);
 277 }
 278
 279 void JsonPrefStore::OnFileRead(base::Value* value_owned,
 280                                PersistentPrefStore::PrefReadError error,
 281                                bool no_dir) {
 282   scoped_ptr<base::Value> value(value_owned);
 283   read_error_ = error;
 284
 285   if (no_dir) {
 286     FOR_EACH_OBSERVER(PrefStore::Observer,
 287                       observers_,
 288                       OnInitializationCompleted(false));
 289     return;
 290   }
 291
 292   initialized_ = true;
 293
 294   switch (error) {
 295     case PREF_READ_ERROR_ACCESS_DENIED:
 296     case PREF_READ_ERROR_FILE_OTHER:
 297     case PREF_READ_ERROR_FILE_LOCKED:
 298     case PREF_READ_ERROR_JSON_TYPE:
 299     case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 300       read_only_ = true;
 301       break;
 302     case PREF_READ_ERROR_NONE:
 303       DCHECK(value.get());
 304       prefs_.reset(static_cast<base::DictionaryValue*>(value.release()));
 305       break;
 306     case PREF_READ_ERROR_NO_FILE:
 307       // If the file just doesn't exist, maybe this is first run.  In any case
 308       // there's no harm in writing out default prefs in this case.
 309       break;
 310     case PREF_READ_ERROR_JSON_PARSE:
 311     case PREF_READ_ERROR_JSON_REPEAT:
 312       break;
 313     default:
 314       NOTREACHED() << "Unknown error: " << error;
 315   }
 316
 317   if (pref_filter_ && pref_filter_->FilterOnLoad(prefs_.get()))
 318     writer_.ScheduleWrite(this);
 319
 320   if (error_delegate_.get() && error != PREF_READ_ERROR_NONE)
 321     error_delegate_->OnError(error);
 322
 323   FOR_EACH_OBSERVER(PrefStore::Observer,
 324                     observers_,
 325                     OnInitializationCompleted(true));
 326 }
 327
 328 JsonPrefStore::~JsonPrefStore() {
 329   CommitPendingWrite();
 330 }
 331
 332 bool JsonPrefStore::SerializeData(std::string* output) {
 333   if (pref_filter_)
 334     pref_filter_->FilterSerializeData(prefs_.get());
 335
 336   JSONStringValueSerializer serializer(output);
 337   serializer.set_pretty_print(true);
 338   return serializer.Serialize(*prefs_);
 339 }