Revert of Move base/prefs to components/prefs

base/prefs/json_pref_store.cc

Index: base/prefs/json_pref_store.cc
diff --git a/base/prefs/json_pref_store.cc b/base/prefs/json_pref_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ffc750ed81b8898f5c51865c8dd38ba02b4d6bbb
--- /dev/null
+++ b/base/prefs/json_pref_store.cc
@@ -0,0 +1,537 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/prefs/json_pref_store.h"
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/json/json_file_value_serializer.h"
+#include "base/json/json_string_value_serializer.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/metrics/histogram.h"
+#include "base/prefs/pref_filter.h"
+#include "base/sequenced_task_runner.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/task_runner_util.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "base/time/default_clock.h"
+#include "base/values.h"
+
+// Result returned from internal read tasks.
+struct JsonPrefStore::ReadResult {
+ public:
+  ReadResult();
+  ~ReadResult();
+
+  scoped_ptr<base::Value> value;
+  PrefReadError error;
+  bool no_dir;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ReadResult);
+};
+
+JsonPrefStore::ReadResult::ReadResult()
+    : error(PersistentPrefStore::PREF_READ_ERROR_NONE), no_dir(false) {
+}
+
+JsonPrefStore::ReadResult::~ReadResult() {
+}
+
+namespace {
+
+// Some extensions we'll tack on to copies of the Preferences files.
+const base::FilePath::CharType kBadExtension[] = FILE_PATH_LITERAL("bad");
+
+PersistentPrefStore::PrefReadError HandleReadErrors(
+    const base::Value* value,
+    const base::FilePath& path,
+    int error_code,
+    const std::string& error_msg) {
+  if (!value) {
+    DVLOG(1) << "Error while loading JSON file: " << error_msg
+             << ", file: " << path.value();
+    switch (error_code) {
+      case JSONFileValueDeserializer::JSON_ACCESS_DENIED:
+        return PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
+      case JSONFileValueDeserializer::JSON_CANNOT_READ_FILE:
+        return PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
+      case JSONFileValueDeserializer::JSON_FILE_LOCKED:
+        return PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
+      case JSONFileValueDeserializer::JSON_NO_SUCH_FILE:
+        return PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
+      default:
+        // JSON errors indicate file corruption of some sort.
+        // Since the file is corrupt, move it to the side and continue with
+        // empty preferences.  This will result in them losing their settings.
+        // We keep the old file for possible support and debugging assistance
+        // as well as to detect if they're seeing these errors repeatedly.
+        // TODO(erikkay) Instead, use the last known good file.
+        base::FilePath bad = path.ReplaceExtension(kBadExtension);
+
+        // If they've ever had a parse error before, put them in another bucket.
+        // TODO(erikkay) if we keep this error checking for very long, we may
+        // want to differentiate between recent and long ago errors.
+        bool bad_existed = base::PathExists(bad);
+        base::Move(path, bad);
+        return bad_existed ? PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT
+                           : PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
+    }
+  }
+  if (!value->IsType(base::Value::TYPE_DICTIONARY))
+    return PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
+  return PersistentPrefStore::PREF_READ_ERROR_NONE;
+}
+
+// Records a sample for |size| in the Settings.JsonDataReadSizeKilobytes
+// histogram suffixed with the base name of the JSON file under |path|.
+void RecordJsonDataSizeHistogram(const base::FilePath& path, size_t size) {
+  std::string spaceless_basename;
+  base::ReplaceChars(path.BaseName().MaybeAsASCII(), " ", "_",
+                     &spaceless_basename);
+
+  // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
+  // macro adapted to allow for a dynamically suffixed histogram name.
+  // Note: The factory creates and owns the histogram.
+  base::HistogramBase* histogram = base::Histogram::FactoryGet(
+      "Settings.JsonDataReadSizeKilobytes." + spaceless_basename, 1, 10000, 50,
+      base::HistogramBase::kUmaTargetedHistogramFlag);
+  histogram->Add(static_cast<int>(size) / 1024);
+}
+
+scoped_ptr<JsonPrefStore::ReadResult> ReadPrefsFromDisk(
+    const base::FilePath& path,
+    const base::FilePath& alternate_path) {
+  if (!base::PathExists(path) && !alternate_path.empty() &&
+      base::PathExists(alternate_path)) {
+    base::Move(alternate_path, path);
+  }
+
+  int error_code;
+  std::string error_msg;
+  scoped_ptr<JsonPrefStore::ReadResult> read_result(
+      new JsonPrefStore::ReadResult);
+  JSONFileValueDeserializer deserializer(path);
+  read_result->value = deserializer.Deserialize(&error_code, &error_msg);
+  read_result->error =
+      HandleReadErrors(read_result->value.get(), path, error_code, error_msg);
+  read_result->no_dir = !base::PathExists(path.DirName());
+
+  if (read_result->error == PersistentPrefStore::PREF_READ_ERROR_NONE)
+    RecordJsonDataSizeHistogram(path, deserializer.get_last_read_size());
+
+  return read_result;
+}
+
+}  // namespace
+
+// static
+scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
+    const base::FilePath& filename,
+    base::SequencedWorkerPool* worker_pool) {
+  std::string token("json_pref_store-");
+  token.append(filename.AsUTF8Unsafe());
+  return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
+      worker_pool->GetNamedSequenceToken(token),
+      base::SequencedWorkerPool::BLOCK_SHUTDOWN);
+}
+
+JsonPrefStore::JsonPrefStore(
+    const base::FilePath& pref_filename,
+    const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
+    scoped_ptr<PrefFilter> pref_filter)
+    : JsonPrefStore(pref_filename,
+                    base::FilePath(),
+                    sequenced_task_runner,
+                    std::move(pref_filter)) {}
+
+JsonPrefStore::JsonPrefStore(
+    const base::FilePath& pref_filename,
+    const base::FilePath& pref_alternate_filename,
+    const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
+    scoped_ptr<PrefFilter> pref_filter)
+    : path_(pref_filename),
+      alternate_path_(pref_alternate_filename),
+      sequenced_task_runner_(sequenced_task_runner),
+      prefs_(new base::DictionaryValue()),
+      read_only_(false),
+      writer_(pref_filename, sequenced_task_runner),
+      pref_filter_(std::move(pref_filter)),
+      initialized_(false),
+      filtering_in_progress_(false),
+      pending_lossy_write_(false),
+      read_error_(PREF_READ_ERROR_NONE),
+      write_count_histogram_(writer_.commit_interval(), path_) {
+  DCHECK(!path_.empty());
+}
+
+bool JsonPrefStore::GetValue(const std::string& key,
+                             const base::Value** result) const {
+  DCHECK(CalledOnValidThread());
+
+  base::Value* tmp = nullptr;
+  if (!prefs_->Get(key, &tmp))
+    return false;
+
+  if (result)
+    *result = tmp;
+  return true;
+}
+
+void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
+  DCHECK(CalledOnValidThread());
+
+  observers_.AddObserver(observer);
+}
+
+void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
+  DCHECK(CalledOnValidThread());
+
+  observers_.RemoveObserver(observer);
+}
+
+bool JsonPrefStore::HasObservers() const {
+  DCHECK(CalledOnValidThread());
+
+  return observers_.might_have_observers();
+}
+
+bool JsonPrefStore::IsInitializationComplete() const {
+  DCHECK(CalledOnValidThread());
+
+  return initialized_;
+}
+
+bool JsonPrefStore::GetMutableValue(const std::string& key,
+                                    base::Value** result) {
+  DCHECK(CalledOnValidThread());
+
+  return prefs_->Get(key, result);
+}
+
+void JsonPrefStore::SetValue(const std::string& key,
+                             scoped_ptr<base::Value> value,
+                             uint32_t flags) {
+  DCHECK(CalledOnValidThread());
+
+  DCHECK(value);
+  base::Value* old_value = nullptr;
+  prefs_->Get(key, &old_value);
+  if (!old_value || !value->Equals(old_value)) {
+    prefs_->Set(key, std::move(value));
+    ReportValueChanged(key, flags);
+  }
+}
+
+void JsonPrefStore::SetValueSilently(const std::string& key,
+                                     scoped_ptr<base::Value> value,
+                                     uint32_t flags) {
+  DCHECK(CalledOnValidThread());
+
+  DCHECK(value);
+  base::Value* old_value = nullptr;
+  prefs_->Get(key, &old_value);
+  if (!old_value || !value->Equals(old_value)) {
+    prefs_->Set(key, std::move(value));
+    ScheduleWrite(flags);
+  }
+}
+
+void JsonPrefStore::RemoveValue(const std::string& key, uint32_t flags) {
+  DCHECK(CalledOnValidThread());
+
+  if (prefs_->RemovePath(key, nullptr))
+    ReportValueChanged(key, flags);
+}
+
+void JsonPrefStore::RemoveValueSilently(const std::string& key,
+                                        uint32_t flags) {
+  DCHECK(CalledOnValidThread());
+
+  prefs_->RemovePath(key, nullptr);
+  ScheduleWrite(flags);
+}
+
+bool JsonPrefStore::ReadOnly() const {
+  DCHECK(CalledOnValidThread());
+
+  return read_only_;
+}
+
+PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
+  DCHECK(CalledOnValidThread());
+
+  return read_error_;
+}
+
+PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
+  DCHECK(CalledOnValidThread());
+
+  OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
+  return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
+                                : read_error_;
+}
+
+void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
+  DCHECK(CalledOnValidThread());
+
+  initialized_ = false;
+  error_delegate_.reset(error_delegate);
+
+  // Weakly binds the read task so that it doesn't kick in during shutdown.
+  base::PostTaskAndReplyWithResult(
+      sequenced_task_runner_.get(),
+      FROM_HERE,
+      base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
+      base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
+}
+
+void JsonPrefStore::CommitPendingWrite() {
+  DCHECK(CalledOnValidThread());
+
+  // Schedule a write for any lossy writes that are outstanding to ensure that
+  // they get flushed when this function is called.
+  SchedulePendingLossyWrites();
+
+  if (writer_.HasPendingWrite() && !read_only_)
+    writer_.DoScheduledWrite();
+}
+
+void JsonPrefStore::SchedulePendingLossyWrites() {
+  if (pending_lossy_write_)
+    writer_.ScheduleWrite(this);
+}
+
+void JsonPrefStore::ReportValueChanged(const std::string& key, uint32_t flags) {
+  DCHECK(CalledOnValidThread());
+
+  if (pref_filter_)
+    pref_filter_->FilterUpdate(key);
+
+  FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
+
+  ScheduleWrite(flags);
+}
+
+void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
+    const base::Closure& on_next_successful_write) {
+  DCHECK(CalledOnValidThread());
+
+  writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
+}
+
+void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
+  DCHECK(CalledOnValidThread());
+
+  DCHECK(read_result);
+
+  scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
+
+  read_error_ = read_result->error;
+
+  bool initialization_successful = !read_result->no_dir;
+
+  if (initialization_successful) {
+    switch (read_error_) {
+      case PREF_READ_ERROR_ACCESS_DENIED:
+      case PREF_READ_ERROR_FILE_OTHER:
+      case PREF_READ_ERROR_FILE_LOCKED:
+      case PREF_READ_ERROR_JSON_TYPE:
+      case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
+        read_only_ = true;
+        break;
+      case PREF_READ_ERROR_NONE:
+        DCHECK(read_result->value.get());
+        unfiltered_prefs.reset(
+            static_cast<base::DictionaryValue*>(read_result->value.release()));
+        break;
+      case PREF_READ_ERROR_NO_FILE:
+        // If the file just doesn't exist, maybe this is first run.  In any case
+        // there's no harm in writing out default prefs in this case.
+      case PREF_READ_ERROR_JSON_PARSE:
+      case PREF_READ_ERROR_JSON_REPEAT:
+        break;
+      case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
+        // This is a special error code to be returned by ReadPrefs when it
+        // can't complete synchronously, it should never be returned by the read
+        // operation itself.
+      case PREF_READ_ERROR_MAX_ENUM:
+        NOTREACHED();
+        break;
+    }
+  }
+
+  if (pref_filter_) {
+    filtering_in_progress_ = true;
+    const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
+        base::Bind(
+            &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
+            initialization_successful));
+    pref_filter_->FilterOnLoad(post_filter_on_load_callback,
+                               std::move(unfiltered_prefs));
+  } else {
+    FinalizeFileRead(initialization_successful, std::move(unfiltered_prefs),
+                     false);
+  }
+}
+
+JsonPrefStore::~JsonPrefStore() {
+  CommitPendingWrite();
+}
+
+bool JsonPrefStore::SerializeData(std::string* output) {
+  DCHECK(CalledOnValidThread());
+
+  pending_lossy_write_ = false;
+
+  write_count_histogram_.RecordWriteOccured();
+
+  if (pref_filter_)
+    pref_filter_->FilterSerializeData(prefs_.get());
+
+  JSONStringValueSerializer serializer(output);
+  // Not pretty-printing prefs shrinks pref file size by ~30%. To obtain
+  // readable prefs for debugging purposes, you can dump your prefs into any
+  // command-line or online JSON pretty printing tool.
+  serializer.set_pretty_print(false);
+  return serializer.Serialize(*prefs_);
+}
+
+void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
+                                     scoped_ptr<base::DictionaryValue> prefs,
+                                     bool schedule_write) {
+  DCHECK(CalledOnValidThread());
+
+  filtering_in_progress_ = false;
+
+  if (!initialization_successful) {
+    FOR_EACH_OBSERVER(PrefStore::Observer,
+                      observers_,
+                      OnInitializationCompleted(false));
+    return;
+  }
+
+  prefs_ = std::move(prefs);
+
+  initialized_ = true;
+
+  if (schedule_write)
+    ScheduleWrite(DEFAULT_PREF_WRITE_FLAGS);
+
+  if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
+    error_delegate_->OnError(read_error_);
+
+  FOR_EACH_OBSERVER(PrefStore::Observer,
+                    observers_,
+                    OnInitializationCompleted(true));
+
+  return;
+}
+
+void JsonPrefStore::ScheduleWrite(uint32_t flags) {
+  if (read_only_)
+    return;
+
+  if (flags & LOSSY_PREF_WRITE_FLAG)
+    pending_lossy_write_ = true;
+  else
+    writer_.ScheduleWrite(this);
+}
+
+// NOTE: This value should NOT be changed without renaming the histogram
+// otherwise it will create incompatible buckets.
+const int32_t
+    JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins = 5;
+
+JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
+    const base::TimeDelta& commit_interval,
+    const base::FilePath& path)
+    : WriteCountHistogram(commit_interval,
+                          path,
+                          scoped_ptr<base::Clock>(new base::DefaultClock)) {
+}
+
+JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
+    const base::TimeDelta& commit_interval,
+    const base::FilePath& path,
+    scoped_ptr<base::Clock> clock)
+    : commit_interval_(commit_interval),
+      path_(path),
+      clock_(clock.release()),
+      report_interval_(
+          base::TimeDelta::FromMinutes(kHistogramWriteReportIntervalMins)),
+      last_report_time_(clock_->Now()),
+      writes_since_last_report_(0) {
+}
+
+JsonPrefStore::WriteCountHistogram::~WriteCountHistogram() {
+  ReportOutstandingWrites();
+}
+
+void JsonPrefStore::WriteCountHistogram::RecordWriteOccured() {
+  ReportOutstandingWrites();
+
+  ++writes_since_last_report_;
+}
+
+void JsonPrefStore::WriteCountHistogram::ReportOutstandingWrites() {
+  base::Time current_time = clock_->Now();
+  base::TimeDelta time_since_last_report = current_time - last_report_time_;
+
+  if (time_since_last_report <= report_interval_)
+    return;
+
+  // If the time since the last report exceeds the report interval, report all
+  // the writes since the last report. They must have all occurred in the same
+  // report interval.
+  base::HistogramBase* histogram = GetHistogram();
+  histogram->Add(writes_since_last_report_);
+
+  // There may be several report intervals that elapsed that don't have any
+  // writes in them. Report these too.
+  int64_t total_num_intervals_elapsed =
+      (time_since_last_report / report_interval_);
+  for (int64_t i = 0; i < total_num_intervals_elapsed - 1; ++i)
+    histogram->Add(0);
+
+  writes_since_last_report_ = 0;
+  last_report_time_ += total_num_intervals_elapsed * report_interval_;
+}
+
+base::HistogramBase* JsonPrefStore::WriteCountHistogram::GetHistogram() {
+  std::string spaceless_basename;
+  base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
+                     &spaceless_basename);
+  std::string histogram_name =
+      "Settings.JsonDataWriteCount." + spaceless_basename;
+
+  // The min value for a histogram is 1. The max value is the maximum number of
+  // writes that can occur in the window being recorded. The number of buckets
+  // used is the max value (plus the underflow/overflow buckets).
+  int32_t min_value = 1;
+  int32_t max_value = report_interval_ / commit_interval_;
+  int32_t num_buckets = max_value + 1;
+
+  // NOTE: These values should NOT be changed without renaming the histogram
+  // otherwise it will create incompatible buckets.
+  DCHECK_EQ(30, max_value);
+  DCHECK_EQ(31, num_buckets);
+
+  // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
+  // macro adapted to allow for a dynamically suffixed histogram name.
+  // Note: The factory creates and owns the histogram.
+  base::HistogramBase* histogram = base::Histogram::FactoryGet(
+      histogram_name, min_value, max_value, num_buckets,
+      base::HistogramBase::kUmaTargetedHistogramFlag);
+  return histogram;
+}