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