[Chromoting] The daemon process now starts the networking process and passes the host configuration…

remoting/host/config_file_watcher.cc

+// 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 "remoting/host/config_file_watcher.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/files/file_path_watcher.h"
+#include "base/file_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/timer.h"
+
+namespace remoting {
+
+// The name of the command-line switch used to specify the host configuration
+// file to use.
+const char kHostConfigSwitchName[] = "host-config";
+
+const FilePath::CharType kDefaultHostConfigFile[] =
+    FILE_PATH_LITERAL("host.json");
+
+class ConfigFileWatcherImpl
+    : public base::RefCountedThreadSafe<ConfigFileWatcherImpl> {
+ public:
+  // Creates a configuration file watcher that lives on the |io_task_runner|
+  // thread but posts config file updates on on |main_task_runner|.
+  ConfigFileWatcherImpl(
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+      ConfigFileWatcher::Delegate* delegate);
+
+  // Starts watching |config_path|.
+  void Watch(const FilePath& config_path);
+
+  // Stops watching the configuration file.
+  void StopWatching();
+
+ private:
+  friend class base::RefCountedThreadSafe<ConfigFileWatcherImpl>;
+  virtual ~ConfigFileWatcherImpl();
+
+  void FinishStopping();
+
+  // Called every time the host configuration file is updated.
+  void OnConfigUpdated(const FilePath& path, bool error);
+
+  // Reads the configuration file and passes it to the delegate.
+  void ReloadConfig();
+
+  FilePath config_path_;
+
+  scoped_ptr<base::DelayTimer<ConfigFileWatcherImpl> > config_updated_timer_;
+
+  // Monitors the host configuration file.
+  scoped_ptr<base::files::FilePathWatcher> config_watcher_;
+
+  base::WeakPtrFactory<ConfigFileWatcher::Delegate> delegate_weak_factory_;
+  base::WeakPtr<ConfigFileWatcher::Delegate> delegate_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConfigFileWatcherImpl);
+};
+
+ConfigFileWatcher::Delegate::~Delegate() {
+}
+
+ConfigFileWatcher::ConfigFileWatcher(
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+    Delegate* delegate)
+    : impl_(new ConfigFileWatcherImpl(main_task_runner,
+                                      io_task_runner, delegate)) {
+}
+
+ConfigFileWatcher::~ConfigFileWatcher() {
+  impl_->StopWatching();
+  impl_ = NULL;
+}
+
+void ConfigFileWatcher::Watch(const FilePath& config_path) {
+  impl_->Watch(config_path);
+}
+
+ConfigFileWatcherImpl::ConfigFileWatcherImpl(
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+    ConfigFileWatcher::Delegate* delegate)
+    : delegate_weak_factory_(delegate),
+      delegate_(delegate_weak_factory_.GetWeakPtr()),
+      main_task_runner_(main_task_runner),
+      io_task_runner_(io_task_runner) {
+  DCHECK(main_task_runner_->BelongsToCurrentThread());
+}
+
+void ConfigFileWatcherImpl::Watch(const FilePath& config_path) {
+  if (!io_task_runner_->BelongsToCurrentThread()) {
+    io_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&ConfigFileWatcherImpl::Watch, this, config_path));
+    return;
+  }
+
+  DCHECK(config_path_.empty());
+  DCHECK(config_updated_timer_.get() == NULL);
+  DCHECK(config_watcher_.get() == NULL);
+
+  // Create the timer that will be used for delayed-reading the configuration
+  // file.
+  config_updated_timer_.reset(new base::DelayTimer<ConfigFileWatcherImpl>(
+      FROM_HERE, base::TimeDelta::FromSeconds(2), this,
+      &ConfigFileWatcherImpl::ReloadConfig));
+
+  // Start watching the configuration file.
+  config_watcher_.reset(new base::files::FilePathWatcher());
+  config_path_ = config_path;
+  if (!config_watcher_->Watch(
+      config_path_,
+      base::Bind(&ConfigFileWatcherImpl::OnConfigUpdated, this))) {
+    LOG(ERROR) << "Couldn't watch file '" << config_path_.value() << "'";
+    main_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&ConfigFileWatcher::Delegate::OnConfigWatcherError,
+                   delegate_));
+    return;
+  }
+
+  // Force reloading of the configuration file at least once.
+  ReloadConfig();
+}
+
+void ConfigFileWatcherImpl::StopWatching() {
+  DCHECK(main_task_runner_->BelongsToCurrentThread());
+
+  delegate_weak_factory_.InvalidateWeakPtrs();
+  io_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&ConfigFileWatcherImpl::FinishStopping, this));
+}
+
+ConfigFileWatcherImpl::~ConfigFileWatcherImpl() {
+  DCHECK(config_updated_timer_.get() == NULL);
+  DCHECK(config_watcher_.get() == NULL);
+}
+
+void ConfigFileWatcherImpl::FinishStopping() {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+
+  config_updated_timer_.reset(NULL);
+  config_watcher_.reset(NULL);
+}
+
+void ConfigFileWatcherImpl::OnConfigUpdated(const FilePath& path, bool error) {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+
+  // Call ReloadConfig() after a short delay, so that we will not try to read
+  // the updated configuration file before it has been completely written.
+  // If the writer moves the new configuration file into place atomically,
+  // this delay may not be necessary.
+  if (!error && config_path_ == path)
+    config_updated_timer_->Reset();
+}
+
+void ConfigFileWatcherImpl::ReloadConfig() {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+
+  std::string config;
+  if (!file_util::ReadFileToString(config_path_, &config)) {
+    LOG(ERROR) << "Failed to read '" << config_path_.value() << "'";
+    main_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&ConfigFileWatcher::Delegate::OnConfigWatcherError,
+                   delegate_));
+    return;
+  }
+
+  main_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&ConfigFileWatcher::Delegate::OnConfigUpdated, delegate_,
+                 config));
+}
+
+}  // namespace remoting