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/files/file_path.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(const base::FilePath& filename,
 128                              base::SequencedTaskRunner* sequenced_task_runner,
 129                              scoped_ptr<PrefFilter> pref_filter)
 130     : path_(filename),
 131       sequenced_task_runner_(sequenced_task_runner),
 132       prefs_(new base::DictionaryValue()),
 133       read_only_(false),
 134       writer_(filename, sequenced_task_runner),
 135       pref_filter_(pref_filter.Pass()),
 136       initialized_(false),
 137       filtering_in_progress_(false),
 138       read_error_(PREF_READ_ERROR_NONE) {
 139 }
 140
 141 JsonPrefStore::JsonPrefStore(const base::FilePath& filename,
 142                              const base::FilePath& alternate_filename,
 143                              base::SequencedTaskRunner* sequenced_task_runner,
 144                              scoped_ptr<PrefFilter> pref_filter)
 145     : path_(filename),
 146       alternate_path_(alternate_filename),
 147       sequenced_task_runner_(sequenced_task_runner),
 148       prefs_(new base::DictionaryValue()),
 149       read_only_(false),
 150       writer_(filename, sequenced_task_runner),
 151       pref_filter_(pref_filter.Pass()),
 152       initialized_(false),
 153       filtering_in_progress_(false),
 154       read_error_(PREF_READ_ERROR_NONE) {
 155 }
 156
 157 bool JsonPrefStore::GetValue(const std::string& key,
 158                              const base::Value** result) const {
 159   DCHECK(CalledOnValidThread());
 160
 161   base::Value* tmp = NULL;
 162   if (!prefs_->Get(key, &tmp))
 163     return false;
 164
 165   if (result)
 166     *result = tmp;
 167   return true;
 168 }
 169
 170 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 171   DCHECK(CalledOnValidThread());
 172
 173   observers_.AddObserver(observer);
 174 }
 175
 176 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 177   DCHECK(CalledOnValidThread());
 178
 179   observers_.RemoveObserver(observer);
 180 }
 181
 182 bool JsonPrefStore::HasObservers() const {
 183   DCHECK(CalledOnValidThread());
 184
 185   return observers_.might_have_observers();
 186 }
 187
 188 bool JsonPrefStore::IsInitializationComplete() const {
 189   DCHECK(CalledOnValidThread());
 190
 191   return initialized_;
 192 }
 193
 194 bool JsonPrefStore::GetMutableValue(const std::string& key,
 195                                     base::Value** result) {
 196   DCHECK(CalledOnValidThread());
 197
 198   return prefs_->Get(key, result);
 199 }
 200
 201 void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
 202   DCHECK(CalledOnValidThread());
 203
 204   DCHECK(value);
 205   scoped_ptr<base::Value> new_value(value);
 206   base::Value* old_value = NULL;
 207   prefs_->Get(key, &old_value);
 208   if (!old_value || !value->Equals(old_value)) {
 209     prefs_->Set(key, new_value.release());
 210     ReportValueChanged(key);
 211   }
 212 }
 213
 214 void JsonPrefStore::SetValueSilently(const std::string& key,
 215                                      base::Value* value) {
 216   DCHECK(CalledOnValidThread());
 217
 218   DCHECK(value);
 219   scoped_ptr<base::Value> new_value(value);
 220   base::Value* old_value = NULL;
 221   prefs_->Get(key, &old_value);
 222   if (!old_value || !value->Equals(old_value)) {
 223     prefs_->Set(key, new_value.release());
 224     if (!read_only_)
 225       writer_.ScheduleWrite(this);
 226   }
 227 }
 228
 229 void JsonPrefStore::RemoveValue(const std::string& key) {
 230   DCHECK(CalledOnValidThread());
 231
 232   if (prefs_->RemovePath(key, NULL))
 233     ReportValueChanged(key);
 234 }
 235
 236 void JsonPrefStore::RemoveValueSilently(const std::string& key) {
 237   DCHECK(CalledOnValidThread());
 238
 239   prefs_->RemovePath(key, NULL);
 240   if (!read_only_)
 241     writer_.ScheduleWrite(this);
 242 }
 243
 244 bool JsonPrefStore::ReadOnly() const {
 245   DCHECK(CalledOnValidThread());
 246
 247   return read_only_;
 248 }
 249
 250 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 251   DCHECK(CalledOnValidThread());
 252
 253   return read_error_;
 254 }
 255
 256 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 257   DCHECK(CalledOnValidThread());
 258
 259   if (path_.empty()) {
 260     scoped_ptr<ReadResult> no_file_result;
 261     no_file_result->error = PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 262     OnFileRead(no_file_result.Pass());
 263     return PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 264   }
 265
 266   OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
 267   return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
 268                                 : read_error_;
 269 }
 270
 271 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
 272   DCHECK(CalledOnValidThread());
 273
 274   initialized_ = false;
 275   error_delegate_.reset(error_delegate);
 276   if (path_.empty()) {
 277     scoped_ptr<ReadResult> no_file_result;
 278     no_file_result->error = PREF_READ_ERROR_FILE_NOT_SPECIFIED;
 279     OnFileRead(no_file_result.Pass());
 280     return;
 281   }
 282
 283   // Weakly binds the read task so that it doesn't kick in during shutdown.
 284   base::PostTaskAndReplyWithResult(
 285       sequenced_task_runner_,
 286       FROM_HERE,
 287       base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
 288       base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
 289 }
 290
 291 void JsonPrefStore::CommitPendingWrite() {
 292   DCHECK(CalledOnValidThread());
 293
 294   if (writer_.HasPendingWrite() && !read_only_)
 295     writer_.DoScheduledWrite();
 296 }
 297
 298 void JsonPrefStore::ReportValueChanged(const std::string& key) {
 299   DCHECK(CalledOnValidThread());
 300
 301   if (pref_filter_)
 302     pref_filter_->FilterUpdate(key);
 303
 304   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 305
 306   if (!read_only_)
 307     writer_.ScheduleWrite(this);
 308 }
 309
 310 void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
 311     const base::Closure& on_next_successful_write) {
 312   DCHECK(CalledOnValidThread());
 313
 314   writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
 315 }
 316
 317 void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
 318   DCHECK(CalledOnValidThread());
 319
 320   DCHECK(read_result);
 321
 322   scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
 323
 324   read_error_ = read_result->error;
 325
 326   bool initialization_successful = !read_result->no_dir;
 327
 328   if (initialization_successful) {
 329     switch (read_error_) {
 330       case PREF_READ_ERROR_ACCESS_DENIED:
 331       case PREF_READ_ERROR_FILE_OTHER:
 332       case PREF_READ_ERROR_FILE_LOCKED:
 333       case PREF_READ_ERROR_JSON_TYPE:
 334       case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 335         read_only_ = true;
 336         break;
 337       case PREF_READ_ERROR_NONE:
 338         DCHECK(read_result->value.get());
 339         unfiltered_prefs.reset(
 340             static_cast<base::DictionaryValue*>(read_result->value.release()));
 341         break;
 342       case PREF_READ_ERROR_NO_FILE:
 343         // If the file just doesn't exist, maybe this is first run.  In any case
 344         // there's no harm in writing out default prefs in this case.
 345         break;
 346       case PREF_READ_ERROR_JSON_PARSE:
 347       case PREF_READ_ERROR_JSON_REPEAT:
 348         break;
 349       case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
 350         // This is a special error code to be returned by ReadPrefs when it
 351         // can't complete synchronously, it should never be returned by the read
 352         // operation itself.
 353         NOTREACHED();
 354         break;
 355       case PREF_READ_ERROR_LEVELDB_IO:
 356       case PREF_READ_ERROR_LEVELDB_CORRUPTION_READ_ONLY:
 357       case PREF_READ_ERROR_LEVELDB_CORRUPTION:
 358         // These are specific to LevelDBPrefStore.
 359         NOTREACHED();
 360       case PREF_READ_ERROR_MAX_ENUM:
 361         NOTREACHED();
 362         break;
 363     }
 364   }
 365
 366   if (pref_filter_) {
 367     filtering_in_progress_ = true;
 368     const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
 369         base::Bind(
 370             &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
 371             initialization_successful));
 372     pref_filter_->FilterOnLoad(post_filter_on_load_callback,
 373                                unfiltered_prefs.Pass());
 374   } else {
 375     FinalizeFileRead(initialization_successful, unfiltered_prefs.Pass(), false);
 376   }
 377 }
 378
 379 JsonPrefStore::~JsonPrefStore() {
 380   CommitPendingWrite();
 381 }
 382
 383 bool JsonPrefStore::SerializeData(std::string* output) {
 384   DCHECK(CalledOnValidThread());
 385
 386   if (pref_filter_)
 387     pref_filter_->FilterSerializeData(prefs_.get());
 388
 389   JSONStringValueSerializer serializer(output);
 390   serializer.set_pretty_print(true);
 391   bool result = serializer.Serialize(*prefs_);
 392
 393   if (result) {
 394     std::string spaceless_basename;
 395     base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
 396                        &spaceless_basename);
 397
 398     // The histogram below is an expansion of the UMA_HISTOGRAM_COUNTS_10000
 399     // macro adapted to allow for a dynamically suffixed histogram name.
 400     // Note: The factory creates and owns the histogram.
 401     base::HistogramBase* histogram =
 402         base::LinearHistogram::FactoryGet(
 403             "Settings.JsonDataSizeKilobytes." + spaceless_basename,
 404             1,
 405             10000,
 406             50,
 407             base::HistogramBase::kUmaTargetedHistogramFlag);
 408     histogram->Add(static_cast<int>(output->size()) / 1024);
 409   }
 410
 411   return result;
 412 }
 413
 414 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
 415                                      scoped_ptr<base::DictionaryValue> prefs,
 416                                      bool schedule_write) {
 417   DCHECK(CalledOnValidThread());
 418
 419   filtering_in_progress_ = false;
 420
 421   if (!initialization_successful) {
 422     FOR_EACH_OBSERVER(PrefStore::Observer,
 423                       observers_,
 424                       OnInitializationCompleted(false));
 425     return;
 426   }
 427
 428   prefs_ = prefs.Pass();
 429
 430   initialized_ = true;
 431
 432   if (schedule_write && !read_only_)
 433     writer_.ScheduleWrite(this);
 434
 435   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
 436     error_delegate_->OnError(read_error_);
 437
 438   FOR_EACH_OBSERVER(PrefStore::Observer,
 439                     observers_,
 440                     OnInitializationCompleted(true));
 441
 442   return;
 443 }