In-browser DNS-based service discovery system

chrome/browser/local_discovery/service_discovery_client_impl.h

+// Copyright (c) 2013 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.
+
+#ifndef CHROME_BROWSER_LOCAL_DISCOVERY_SERVICE_DISCOVERY_CLIENT_IMPL_H_
+#define CHROME_BROWSER_LOCAL_DISCOVERY_SERVICE_DISCOVERY_CLIENT_IMPL_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/cancelable_callback.h"
+#include "base/memory/linked_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/message_loop.h"
+#include "chrome/browser/local_discovery/service_discovery_client.h"
+#include "net/dns/mdns_client.h"
+
+namespace local_discovery {
+
+class ServiceDiscoveryClientImpl : public ServiceDiscoveryClient {
+ public:
+  ServiceDiscoveryClientImpl();
+  virtual ~ServiceDiscoveryClientImpl();
+
+  // ServiceDiscoveryClient implementation:
+  virtual scoped_ptr<ServiceWatcher> CreateServiceWatcher(
+      const std::string& service_type,
+      ServiceWatcher::Delegate* delegate) OVERRIDE;
+
+  virtual scoped_ptr<ServiceResolver> CreateServiceResolver(
+      const std::string& service_name,
+      const ServiceResolver::ResolveCompleteCallback& callback) OVERRIDE;
+
+  static ServiceDiscoveryClientImpl* GetInstance();
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ServiceDiscoveryClientImpl);
+};
+
+class ServiceWatcherImpl : public ServiceWatcher,
+                               public net::MDnsListener::Delegate {

[gene, 2013/06/19 22:48:03]

not sure what is the correct indentation here

[Vitaly Buka (NO REVIEWS), 2013/06/19 22:55:21]

all publics must be aligned

[Noam Samuel, 2013/06/19 23:53:29]

Done.

+ public:
+  ServiceWatcherImpl(const std::string& service_type,
+                     ServiceWatcher::Delegate* delegate);
+  // Listening will automatically stop when the destructor is called.
+  virtual ~ServiceWatcherImpl();
+
+  // ServiceWatcher implementation:
+  virtual bool Start() OVERRIDE;
+
+  virtual void GetAvailableServices(
+      std::vector<std::string>* services) const OVERRIDE;
+
+  virtual void DiscoverNewServices(bool force_update) OVERRIDE;
+
+  virtual std::string GetServiceType() const OVERRIDE;
+
+  virtual void ReadCachedServices() OVERRIDE;
+
+  virtual void OnRecordUpdate(net::MDnsListener::UpdateType update,
+                              const net::RecordParsed* record) OVERRIDE;
+
+  virtual void OnNsecRecord(const std::string& name, unsigned rrtype) OVERRIDE;
+
+  virtual void OnCachePurged() OVERRIDE;
+
+  virtual void OnTransactionResponse(
+      scoped_ptr<net::MDnsTransaction>* transaction,
+      net::MDnsTransaction::Result result,
+      const net::RecordParsed* record);
+
+ private:
+  struct ServiceListeners {
+    ServiceListeners(const std::string& service_name,
+                     ServiceWatcherImpl* watcher);
+    ~ServiceListeners();
+    bool Start();
+
+   private:
+    scoped_ptr<net::MDnsListener> srv_listener_;
+    scoped_ptr<net::MDnsListener> txt_listener_;
+  };
+
+  typedef std::map<std::string, linked_ptr<ServiceListeners>>
+      ServiceListenersMap;
+
+  void AddService(const std::string& service);
+  void RemoveService(const std::string& service);
+  bool CreateTransaction(bool active, bool alert_existing_services,
+                         bool force_refresh,
+                         scoped_ptr<net::MDnsTransaction>* transaction);
+
+  std::string service_type_;
+  ServiceListenersMap services_;
+  scoped_ptr<net::MDnsTransaction> transaction_network_;
+  scoped_ptr<net::MDnsTransaction> transaction_cache_;
+  scoped_ptr<net::MDnsListener> listener_;
+
+  ServiceWatcher::Delegate* delegate_;
+  bool started_;
+
+  DISALLOW_COPY_AND_ASSIGN(ServiceWatcherImpl);
+};
+
+
+class ServiceResolverImpl
+    : public ServiceResolver,
+      public base::SupportsWeakPtr<ServiceResolverImpl> {
+ public:
+  ServiceResolverImpl(const std::string& service_name,
+                      const ServiceResolver::ResolveCompleteCallback& callback);
+
+  virtual ~ServiceResolverImpl();
+
+  // ServiceResolver implementation:
+  virtual bool StartResolving() OVERRIDE;
+
+  virtual bool IsResolving() const OVERRIDE;
+
+  virtual bool HasResolved() const OVERRIDE;
+
+  virtual std::string GetName() const OVERRIDE;
+
+  virtual const ServiceDescription& GetServiceDescription() const OVERRIDE;
+
+ private:
+  ServiceDescription* staging_service() {
+    return &services_[(current_service_index_ + 1) % 2];
+  }
+
+  // Respond to transaction finishing for SRV records.
+  void SrvRecordTransactionResponse(net::MDnsTransaction::Result status,
+                                    const net::RecordParsed* record);
+
+  // Respond to transaction finishing for TXT records.
+  void TxtRecordTransactionResponse(net::MDnsTransaction::Result status,
+                                    const net::RecordParsed* record);
+
+  // Respond to transaction finishing for A records.
+  void ARecordTransactionResponse(net::MDnsTransaction::Result status,
+                                  const net::RecordParsed* record);
+
+  void AlertCallbackIfReady();
+
+  // Convert a TXT record to a vector of strings (metadata).
+  const std::vector<std::string>& RecordToMetadata(
+      const net::RecordParsed* record) const;
+
+  // Convert an SRV record to a host and port pair.
+  net::HostPortPair RecordToAddress(
+      const net::RecordParsed* record) const;
+
+  // Convert an A record to an IP address.
+  const net::IPAddressNumber& RecordToIPAddress(
+      const net::RecordParsed* record) const;
+
+  // Convert an MDns status to a service discovery status.
+  RequestStatus MDnsStatusToRequestStatus(
+      net::MDnsTransaction::Result status) const;
+
+  bool CreateTxtTransaction();
+  bool CreateSrvTransaction();
+  void CreateATransaction();
+
+  std::string service_name_;
+  ResolveCompleteCallback callback_;
+
+  bool is_resolving_;
+  bool has_resolved_;
+
+  bool metadata_resolved_;
+  bool address_resolved_;
+
+  scoped_ptr<net::MDnsTransaction> txt_transaction_;
+  scoped_ptr<net::MDnsTransaction> srv_transaction_;
+  scoped_ptr<net::MDnsTransaction> a_transaction_;
+
+  ServiceDescription services_[2];

[gene, 2013/06/19 22:48:03]

This is a bit confusing, a few alternatives are:
1. Have staging_service_ and final_service_. Implement swap() function in
ServiceDescription (string and vector already supports swap)

2. Have staging_service_ and final_service_. Implement StagingToFinal() function
in this class.

3. Have scoped_ptr<ServiceDescription> staging_service_ and final_service_.
scoped_ptr already supports swap().

[Noam Samuel, 2013/06/19 23:53:29]

Done.

+  int current_service_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(ServiceResolverImpl);
+};
+
+}  // namespace local_discovery
+
+#endif  // CHROME_BROWSER_LOCAL_DISCOVERY_SERVICE_DISCOVERY_CLIENT_IMPL_H_