Added DnsQuery class

net/base/dns_query.h

+// 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.
+
+#ifndef NET_BASE_DNS_QUERY_H_
+#define NET_BASE_DNS_QUERY_H_
+#pragma once
+
+#include <string>
+
+#include "net/base/address_family.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_util.h"
+
+namespace net{
+
+// A class that encapsulates bits and pieces related to DNS request processing.
+class DnsQuery {
+ public:
+  // Constructs an object containing an IOBuffer with raw DNS query string
+  // for |hostname| with the given |address_family|; |port| is here due to
+  // legacy -- getaddrinfo() takes service name, which is mapped to some
+  // port and returns sockaddr_in structures with ports filled in, so do we
+  // -- look at DnsResponse::Parse() to see where it is used.
+
+  // Every generated object has a random ID, hence two objects generated
+  // with the same set of constructor arguments are generally not equal;
+  // there is a 1/2^16 chance of them being equal due to size of |id_|.
+  DnsQuery(const std::string& hostname, AddressFamily address_family, int port);
+
+  // Returns true if the constructed object was valid.
+  bool IsValid() const { return io_buffer_.get() != NULL; }
+
+  // DnsQuery field accessors.  These should only be called on an object
+  // for whom |IsValid| is true.
+  int port() const;
+  uint16 id() const;
+  uint16 qtype() const;
+  AddressFamily address_family() const;
+  const std::string& hostname() const;
+
+  // IOBuffer accessor to be used for writing out the query.
+  IOBufferWithSize* io_buffer() const;
+
+ private:
+  // Port to be used by corresponding DnsResponse when filling sockaddr_ins
+  // to be returned.
+  int port_;
+
+  // ID of the query.
+  uint16 id_;
+
+  // Type of query, currently, either A or AAAA.
+  uint16 qtype_;
+
+  // Address family of the query; used when constructing new object from
+  // this one.
+  AddressFamily address_family_;
+
+  // Hostname that we are trying to resolve.
+  std::string hostname_;
+
+  // Contains query bytes to be consumed by higher level Write() call.
+  scoped_refptr<IOBufferWithSize> io_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsQuery);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_DNS_QUERY_H_