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/sequenced_task_runner.h"
  17 #include "base/threading/sequenced_worker_pool.h"
  18 #include "base/values.h"
  19
  20 namespace {
  21
  22 // Some extensions we'll tack on to copies of the Preferences files.
  23 const base::FilePath::CharType* kBadExtension = FILE_PATH_LITERAL("bad");
  24
  25 // Differentiates file loading between origin thread and passed
  26 // (aka file) thread.
  27 class 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
  95 void 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
 143 scoped_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
 153 JsonPrefStore::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
 163 bool 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
 174 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 175   observers_.AddObserver(observer);
 176 }
 177
 178 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 179   observers_.RemoveObserver(observer);
 180 }
 181
 182 bool JsonPrefStore::HasObservers() const {
 183   return observers_.might_have_observers();
 184 }
 185
 186 bool JsonPrefStore::IsInitializationComplete() const {
 187   return initialized_;
 188 }
 189
 190 bool JsonPrefStore::GetMutableValue(const std::string& key,
 191                                     base::Value** result) {
 192   return prefs_->Get(key, result);
 193 }
 194
 195 void 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
 206 void 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
 219 void JsonPrefStore::RemoveValue(const std::string& key) {
 220   if (prefs_->RemovePath(key, NULL))
 221     ReportValueChanged(key);
 222 }
 223
 224 bool JsonPrefStore::ReadOnly() const {
 225   return read_only_;
 226 }
 227
 228 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 229   return read_error_;
 230 }
 231
 232 PersistentPrefStore::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
 246 void 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
 261 void JsonPrefStore::CommitPendingWrite() {
 262   if (writer_.HasPendingWrite() && !read_only_)
 263     writer_.DoScheduledWrite();
 264 }
 265
 266 void 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
 272 void 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
 318 JsonPrefStore::~JsonPrefStore() {
 319   CommitPendingWrite();
 320 }
 321
 322 bool JsonPrefStore::SerializeData(std::string* output) {
 323   JSONStringValueSerializer serializer(output);
 324   serializer.set_pretty_print(true);
 325   return serializer.Serialize(*prefs_);
 326 }