Implement browser-side host resolver Mojo service.

net/dns/mojo_host_resolver_impl.cc

+// Copyright 2015 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 "net/dns/mojo_host_resolver_impl.h"
+
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "base/stl_util.h"
+#include "net/base/address_list.h"
+#include "net/base/net_errors.h"
+#include "net/dns/host_resolver.h"
+#include "net/dns/type_converters.h"
+
+namespace net {
+
+// Handles host resolution for a single request and sends a response when done.
+// Also detects connection errors for HostResolverRequestClient and cancels the
+// outstanding resolve request. Owned by MojoHostResolverImpl.
+class MojoHostResolverImpl::Job : public mojo::ErrorHandler {
+ public:
+  Job(base::WeakPtr<MojoHostResolverImpl> resolver_service,
+      net::HostResolver* resolver,
+      const net::HostResolver::RequestInfo& request_info,
+      interfaces::HostResolverRequestClientPtr client);
+  ~Job() override;
+
+ private:
+  // Completion callback for the HostResolver::Resolve request.
+  void OnResolveDone(int result);
+
+  // Overridden from mojo::ErrorHandler:
+  void OnConnectionError() override;
+
+  base::WeakPtr<MojoHostResolverImpl> resolver_service_;
+  net::HostResolver* resolver_;
+  net::HostResolver::RequestInfo request_info_;
+  interfaces::HostResolverRequestClientPtr client_;
+  net::HostResolver::RequestHandle handle_;
+  AddressList result_;
+  base::ThreadChecker thread_checker_;
+};
+
+MojoHostResolverImpl::MojoHostResolverImpl(net::HostResolver* resolver)
+    : resolver_(resolver), weak_factory_(this) {
+}
+
+MojoHostResolverImpl::~MojoHostResolverImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  STLDeleteElements(&pending_jobs_);
+}
+
+void MojoHostResolverImpl::Resolve(
+    interfaces::HostResolverRequestInfoPtr request_info,
+    interfaces::HostResolverRequestClientPtr client) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  Job* job = new Job(weak_factory_.GetWeakPtr(), resolver_,
+                     request_info->To<net::HostResolver::RequestInfo>(),
+                     client.Pass());
+  pending_jobs_.insert(job);
+}
+
+void MojoHostResolverImpl::DeleteJob(Job* job) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (ContainsKey(pending_jobs_, job)) {
+    size_t num_erased = pending_jobs_.erase(job);

[Sam McNally, 2015/02/06 07:12:32]

Please use the iterator erase overload. Doing two lookups is wasteful.

[Anand Mistry (off Chromium), 2015/02/08 23:09:21]

I've gone back to having a Start() method. I realised that the current approach
creates an ABA problem.

+    DCHECK(num_erased);
+    delete job;
+  }
+}
+
+MojoHostResolverImpl::Job::Job(
+    base::WeakPtr<MojoHostResolverImpl> resolver_service,
+    net::HostResolver* resolver,
+    const net::HostResolver::RequestInfo& request_info,
+    interfaces::HostResolverRequestClientPtr client)
+    : resolver_service_(resolver_service),
+      resolver_(resolver),
+      request_info_(request_info),
+      client_(client.Pass()),
+      handle_(nullptr) {
+  client_.set_error_handler(this);
+
+  DVLOG(1) << "Resolve " << request_info_.host_port_pair().ToString();
+  BoundNetLog net_log;
+  int result =
+      resolver_->Resolve(request_info_, DEFAULT_PRIORITY, &result_,
+                         base::Bind(&MojoHostResolverImpl::Job::OnResolveDone,
+                                    base::Unretained(this)),
+                         &handle_, net_log);
+
+  if (result != ERR_IO_PENDING)
+    OnResolveDone(result);
+}
+
+MojoHostResolverImpl::Job::~Job() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (handle_)
+    resolver_->CancelRequest(handle_);
+}
+
+void MojoHostResolverImpl::Job::OnResolveDone(int result) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  handle_ = nullptr;
+  DVLOG(1) << "Resolved " << request_info_.host_port_pair().ToString()
+           << " with error " << result << " and " << result_.size()
+           << " results!";
+  for (const auto& address : result_) {
+    VLOG(1) << address.ToString();
+  }
+  if (result)
+    client_->ReportResult(result, nullptr);
+  else
+    client_->ReportResult(0, interfaces::AddressList::From(result_));
+
+  // We could have been called inline with the constructor, so delay
+  // destruction.
+  base::MessageLoopProxy::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&MojoHostResolverImpl::DeleteJob, resolver_service_, this));
+}
+
+void MojoHostResolverImpl::Job::OnConnectionError() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // |resolver_service_| should always outlive us.
+  DCHECK(resolver_service_);
+  DVLOG(1) << "Connection error on request for "
+           << request_info_.host_port_pair().ToString();
+  resolver_service_->DeleteJob(this);
+}
+
+}  // namespace net