src/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/files/file_path.h"
  12 #include "base/files/file_util.h"
  13 #include "base/json/json_file_value_serializer.h"
  14 #include "base/json/json_string_value_serializer.h"
  15 #include "base/memory/ref_counted.h"
  16 #include "base/metrics/histogram.h"
  17 #include "base/prefs/pref_filter.h"
  18 #include "base/sequenced_task_runner.h"
  19 #include "base/strings/string_util.h"
  20 #include "base/task_runner_util.h"
  21 #include "base/threading/sequenced_worker_pool.h"
  22 #include "base/values.h"
  23
  24 // Result returned from internal read tasks.
  25 struct JsonPrefStore::ReadResult {
  26  public:
  27   ReadResult();
  28   ~ReadResult();
  29
  30   scoped_ptr<base::Value> value;
  31   PrefReadError error;
  32   bool no_dir;
  33
  34  private:
  35   DISALLOW_COPY_AND_ASSIGN(ReadResult);
  36 };
  37
  38 JsonPrefStore::ReadResult::ReadResult()
  39     : error(PersistentPrefStore::PREF_READ_ERROR_NONE), no_dir(false) {
  40 }
  41
  42 JsonPrefStore::ReadResult::~ReadResult() {
  43 }
  44
  45 namespace {
  46
  47 // Some extensions we'll tack on to copies of the Preferences files.
  48 const base::FilePath::CharType kBadExtension[] = FILE_PATH_LITERAL("bad");
  49
  50 PersistentPrefStore::PrefReadError HandleReadErrors(
  51     const base::Value* value,
  52     const base::FilePath& path,
  53     int error_code,
  54     const std::string& error_msg) {
  55   if (!value) {
  56     DVLOG(1) << "Error while loading JSON file: " << error_msg
  57              << ", file: " << path.value();
  58     switch (error_code) {
  59       case JSONFileValueSerializer::JSON_ACCESS_DENIED:
  60         return PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
  61         break;
  62       case JSONFileValueSerializer::JSON_CANNOT_READ_FILE:
  63         return PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
  64         break;
  65       case JSONFileValueSerializer::JSON_FILE_LOCKED:
  66         return PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
  67         break;
  68       case JSONFileValueSerializer::JSON_NO_SUCH_FILE:
  69         return PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
  70         break;
  71       default:
  72         // JSON errors indicate file corruption of some sort.
  73         // Since the file is corrupt, move it to the side and continue with
  74         // empty preferences.  This will result in them losing their settings.
  75         // We keep the old file for possible support and debugging assistance
  76         // as well as to detect if they're seeing these errors repeatedly.
  77         // TODO(erikkay) Instead, use the last known good file.
  78         base::FilePath bad = path.ReplaceExtension(kBadExtension);
  79
  80         // If they've ever had a parse error before, put them in another bucket.
  81         // TODO(erikkay) if we keep this error checking for very long, we may
  82         // want to differentiate between recent and long ago errors.
  83         bool bad_existed = base::PathExists(bad);
  84         base::Move(path, bad);
  85         return bad_existed ? PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT
  86                            : PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
  87     }
  88   } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
  89     return PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
  90   }
  91   return PersistentPrefStore::PREF_READ_ERROR_NONE;
  92 }
  93
  94 scoped_ptr<JsonPrefStore::ReadResult> ReadPrefsFromDisk(
  95     const base::FilePath& path,
  96     const base::FilePath& alternate_path) {
  97   if (!base::PathExists(path) && !alternate_path.empty() &&
  98       base::PathExists(alternate_path)) {
  99     base::Move(alternate_path, path);
 100   }
 101
 102   int error_code;
 103   std::string error_msg;
 104   scoped_ptr<JsonPrefStore::ReadResult> read_result(
 105       new JsonPrefStore::ReadResult);
 106   JSONFileValueSerializer serializer(path);
 107   read_result->value.reset(serializer.Deserialize(&error_code, &error_msg));
 108   read_result->error =
 109       HandleReadErrors(read_result->value.get(), path, error_code, error_msg);
 110   read_result->no_dir = !base::PathExists(path.DirName());
 111   return read_result.Pass();
 112 }
 113
 114 }  // namespace
 115
 116 // static
 117 scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
 118     const base::FilePath& filename,
 119     base::SequencedWorkerPool* worker_pool) {
 120   std::string token("json_pref_store-");
 121   token.append(filename.AsUTF8Unsafe());
 122   return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
 123       worker_pool->GetNamedSequenceToken(token),
 124       base::SequencedWorkerPool::BLOCK_SHUTDOWN);
 125 }
 126
 127 JsonPrefStore::JsonPrefStore(
 128     const base::FilePath& filename,
 129     const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
 130     scoped_ptr<PrefFilter> pref_filter)
 131     : path_(filename),
 132       sequenced_task_runner_(sequenced_task_runner),
 133       prefs_(new base::DictionaryValue()),
 134       read_only_(false),
 135       writer_(filename, sequenced_task_runner),
 136       pref_filter_(pref_filter.Pass()),
 137       initialized_(false),
 138       filtering_in_progress_(false),
 139       read_error_(PREF_READ_ERROR_NONE) {
 140 }
 141
 142 JsonPrefStore::JsonPrefStore(
 143     const base::FilePath& filename,
 144     const base::FilePath& alternate_filename,
 145     const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
 146     scoped_ptr<PrefFilter> pref_filter)
 147     : path_(filename),
 148       alternate_path_(alternate_filename),
 149       sequenced_task_runner_(sequenced_task_runner),
 150       prefs_(new base::DictionaryValue()),
 151       read_only_(false),
 152       writer_(filename, sequenced_task_runner),
 153       pref_filter_(pref_filter.Pass()),
 154       initialized_(false),
 155       filtering_in_progress_(false),
 156       read_error_(PREF_READ_ERROR_NONE) {
 157 }
 158
 159 bool JsonPrefStore::GetValue(const std::string& key,
 160                              const base::Value** result) const {
 161   DCHECK(CalledOnValidThread());
 162
 163   base::Value* tmp = NULL;
 164   if (!prefs_->Get(key, &tmp))
 165     return false;
 166
 167   if (result)
 168     *result = tmp;
 169   return true;
 170 }
 171
 172 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 173   DCHECK(CalledOnValidThread());
 174
 175   observers_.AddObserver(observer);
 176 }
 177
 178 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 179   DCHECK(CalledOnValidThread());
 180
 181   observers_.RemoveObserver(observer);
 182 }
 183
 184 bool JsonPrefStore::HasObservers() const {
 185   DCHECK(CalledOnValidThread());
 186
 187   return observers_.might_have_observers();
 188 }
 189
 190 bool JsonPrefStore::IsInitializationComplete() const {
 191   DCHECK(CalledOnValidThread());
 192
 193   return initialized_;
 194 }
 195
 196 bool JsonPrefStore::GetMutableValue(const std::string& key,
 197                                     base::Value** result) {
 198   DCHECK(CalledOnValidThread());
 199
 200   return prefs_->Get(key, result);
 201 }
 202
 203 void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
 204   DCHECK(CalledOnValidThread());
 205
 206   DCHECK(value);
 207   scoped_ptr<base::Value> new_value(value);
 208   base::Value* old_value = NULL;
 209   prefs_->Get(key, &old_value);
 210   if (!old_value || !value->Equals(old_value)) {
 211     prefs_->Set(key, new_value.release());
 212     ReportValueChanged(key);
 213   }
 214 }
 215
 216 void JsonPrefStore::SetValueSilently(const std::string& key,
 217                                      base::Value* value) {
 218   DCHECK(CalledOnValidThread());
 219
 220   DCHECK(value);
 221   scoped_ptr<base::Value> new_value(value);
 222   base::Value* old_value = NULL;
 223   prefs_->Get(key, &old_value);
 224   if (!old_value || !value->Equals(old_value)) {
 225     prefs_->Set(key, new_value.release());
 226     if (!read_only_)
 227       writer_.ScheduleWrite(this);
 228   }
 229 }
 230
 231 void JsonPrefStore::RemoveValue(const std::string& key) {
 232   DCHECK(CalledOnValidThread());
 233
 234   if (prefs_->RemovePath(key, NULL))
 235     ReportValueChanged(key);
 236 }
 237
 238 void JsonPrefStore::RemoveValueSilently(const std::string& key) {
 239   DCHECK(CalledOnValidThread());
 240
 241   prefs_->RemovePath(key, NULL);
 242   if (!read_only_)
 243     writer_.ScheduleWrite(this);
 244 }
 245
 246 bool JsonPrefStore::ReadOnly() const {
 247   DCHECK(CalledOnValidThread());
 248
 249   return read_only_;
 250 }
 251
 252 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 253   DCHECK(CalledOnValidThread());
 254
 255   return read_error_;
 256 }
 257
 258 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 259   DCHECK(CalledOnValidThread());
 260
 261   if (path_.empty()) {
 262     scoped_ptr<ReadResult> no_file_result;
 263     no_file_result->error = PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 264     OnFileRead(no_file_result.Pass());
 265     return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 266   }
 267
 268   OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
 269   return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
 270                                 : read_error_;
 271 }
 272
 273 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
 274   DCHECK(CalledOnValidThread());
 275
 276   initialized_ = false;
 277   error_delegate_.reset(error_delegate);
 278   if (path_.empty()) {
 279     scoped_ptr<ReadResult> no_file_result;
 280     no_file_result->error = PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 281     OnFileRead(no_file_result.Pass());
 282     return;
 283   }
 284
 285   // Weakly binds the read task so that it doesn't kick in during shutdown.
 286   base::PostTaskAndReplyWithResult(
 287       sequenced_task_runner_.get(),
 288       FROM_HERE,
 289       base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
 290       base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
 291 }
 292
 293 void JsonPrefStore::CommitPendingWrite() {
 294   DCHECK(CalledOnValidThread());
 295
 296   if (writer_.HasPendingWrite() && !read_only_)
 297     writer_.DoScheduledWrite();
 298 }
 299
 300 void JsonPrefStore::ReportValueChanged(const std::string& key) {
 301   DCHECK(CalledOnValidThread());
 302
 303   if (pref_filter_)
 304     pref_filter_->FilterUpdate(key);
 305
 306   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 307
 308   if (!read_only_)
 309     writer_.ScheduleWrite(this);
 310 }
 311
 312 void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
 313     const base::Closure& on_next_successful_write) {
 314   DCHECK(CalledOnValidThread());
 315
 316   writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
 317 }
 318
 319 void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
 320   DCHECK(CalledOnValidThread());
 321
 322   DCHECK(read_result);
 323
 324   scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
 325
 326   read_error_ = read_result->error;
 327
 328   bool initialization_successful = !read_result->no_dir;
 329
 330   if (initialization_successful) {
 331     switch (read_error_) {
 332       case PREF_READ_ERROR_ACCESS_DENIED:
 333       case PREF_READ_ERROR_FILE_OTHER:
 334       case PREF_READ_ERROR_FILE_LOCKED:
 335       case PREF_READ_ERROR_JSON_TYPE:
 336       case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 337         read_only_ = true;
 338         break;
 339       case PREF_READ_ERROR_NONE:
 340         DCHECK(read_result->value.get());
 341         unfiltered_prefs.reset(
 342             static_cast<base::DictionaryValue*>(read_result->value.release()));
 343         break;
 344       case PREF_READ_ERROR_NO_FILE:
 345         // If the file just doesn't exist, maybe this is first run.  In any case
 346         // there's no harm in writing out default prefs in this case.
 347         break;
 348       case PREF_READ_ERROR_JSON_PARSE:
 349       case PREF_READ_ERROR_JSON_REPEAT:
 350         break;
 351       case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
 352         // This is a special error code to be returned by ReadPrefs when it
 353         // can't complete synchronously, it should never be returned by the read
 354         // operation itself.
 355         NOTREACHED();
 356         break;
 357       case PREF_READ_ERROR_LEVELDB_IO:
 358       case PREF_READ_ERROR_LEVELDB_CORRUPTION_READ_ONLY:
 359       case PREF_READ_ERROR_LEVELDB_CORRUPTION:
 360         // These are specific to LevelDBPrefStore.
 361         NOTREACHED();
 362       case PREF_READ_ERROR_MAX_ENUM:
 363         NOTREACHED();
 364         break;
 365     }
 366   }
 367
 368   if (pref_filter_) {
 369     filtering_in_progress_ = true;
 370     const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
 371         base::Bind(
 372             &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
 373             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
 381 JsonPrefStore::~JsonPrefStore() {
 382   CommitPendingWrite();
 383 }
 384
 385 bool JsonPrefStore::SerializeData(std::string* output) {
 386   DCHECK(CalledOnValidThread());
 387
 388   if (pref_filter_)
 389     pref_filter_->FilterSerializeData(prefs_.get());
 390
 391   JSONStringValueSerializer serializer(output);
 392   serializer.set_pretty_print(true);
 393   bool result = serializer.Serialize(*prefs_);
 394
 395   if (result) {
 396     std::string spaceless_basename;
 397     base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
 398                        &spaceless_basename);
 399
 400     // The histogram below is an expansion of the UMA_HISTOGRAM_COUNTS_10000
 401     // macro adapted to allow for a dynamically suffixed histogram name.
 402     // Note: The factory creates and owns the histogram.
 403     base::HistogramBase* histogram =
 404         base::LinearHistogram::FactoryGet(
 405             "Settings.JsonDataSizeKilobytes." + spaceless_basename,
 406             1,
 407             10000,
 408             50,
 409             base::HistogramBase::kUmaTargetedHistogramFlag);
 410     histogram->Add(static_cast<int>(output->size()) / 1024);
 411   }
 412
 413   return result;
 414 }
 415
 416 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
 417                                      scoped_ptr<base::DictionaryValue> prefs,
 418                                      bool schedule_write) {
 419   DCHECK(CalledOnValidThread());
 420
 421   filtering_in_progress_ = false;
 422
 423   if (!initialization_successful) {
 424     FOR_EACH_OBSERVER(PrefStore::Observer,
 425                       observers_,
 426                       OnInitializationCompleted(false));
 427     return;
 428   }
 429
 430   prefs_ = prefs.Pass();
 431
 432   initialized_ = true;
 433
 434   if (schedule_write && !read_only_)
 435     writer_.ScheduleWrite(this);
 436
 437   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
 438     error_delegate_->OnError(read_error_);
 439
 440   FOR_EACH_OBSERVER(PrefStore::Observer,
 441                     observers_,
 442                     OnInitializationCompleted(true));
 443
 444   return;
 445 }