Isolates generic DnsClient from AsyncHostResolver.

DnsClient provides a generic DNS client that allows fetching resource records. 
DnsClient is very lightweight and does not support aggregation, queuing or 
prioritization of requests. 

This is the first CL in a series to merge AsyncHostResolver into 
HostResolverImpl. 

Also introduces general-purpose BigEndianReader/Writer. 

BUG=90881
TEST=./net_unittests


Review URL: http://codereview.chromium.org/8762001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113282 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 91 insertions, 0 deletions

diff --git a/net/dns/dns_client.cc b/net/dns/dns_client.cc
new file mode 100644
index 0000000..de60cc3
--- /dev/null
+++ b/net/dns/dns_client.cc
@@ -0,0 +1,91 @@
+// Copyright (c) 2011 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/dns_client.h"
+
+#include "base/bind.h"
+#include "base/string_piece.h"
+#include "net/base/net_errors.h"
+#include "net/dns/dns_response.h"
+#include "net/dns/dns_session.h"
+#include "net/dns/dns_transaction.h"
+#include "net/socket/client_socket_factory.h"
+
+namespace net {
+
+DnsClient::Request::Request(const base::StringPiece& qname,
+                            uint16 qtype,
+                            const RequestCallback& callback)
+    : qname_(qname.data(), qname.size()),
+      qtype_(qtype),
+      callback_(callback) {
+}
+
+DnsClient::Request::~Request() {}
+
+// Implementation of DnsClient that uses DnsTransaction to serve requests.
+class DnsClientImpl : public DnsClient {
+ public:
+  class RequestImpl : public Request {
+   public:
+    RequestImpl(const base::StringPiece& qname,
+                uint16 qtype,
+                const RequestCallback& callback,
+                DnsSession* session,
+                const BoundNetLog& net_log)
+        : Request(qname, qtype, callback),
+          session_(session),
+          net_log_(net_log) {
+    }
+
+    virtual int Start() OVERRIDE {
+      transaction_.reset(new DnsTransaction(
+          session_,
+          qname(),
+          qtype(),
+          base::Bind(&RequestImpl::OnComplete, base::Unretained(this)),
+          net_log_));
+      return transaction_->Start();
+    }
+
+    void OnComplete(DnsTransaction* transaction, int rv) {
+      DCHECK_EQ(transaction_.get(), transaction);
+      // TODO(szym):
+      // - handle retransmissions here instead of DnsTransaction
+      // - handle rcode and flags here instead of DnsTransaction
+      // - update RTT in DnsSession
+      // - perform suffix search
+      // - handle DNS over TCP
+      DoCallback(rv, (rv == OK) ? transaction->response() : NULL);
+    }
+
+   private:
+    scoped_refptr<DnsSession> session_;
+    BoundNetLog net_log_;
+    scoped_ptr<DnsTransaction> transaction_;
+  };
+
+  explicit DnsClientImpl(DnsSession* session) {
+    session_ = session;
+  }
+
+  virtual Request* CreateRequest(
+      const base::StringPiece& qname,
+      uint16 qtype,
+      const RequestCallback& callback,
+      const BoundNetLog& source_net_log) OVERRIDE {
+    return new RequestImpl(qname, qtype, callback, session_, source_net_log);
+  }
+
+ private:
+  scoped_refptr<DnsSession> session_;
+};
+
+// static
+DnsClient* DnsClient::CreateClient(DnsSession* session) {
+  return new DnsClientImpl(session);
+}
+
+}  // namespace net
+