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, 98 insertions, 0 deletions

diff --git a/net/base/big_endian.cc b/net/base/big_endian.cc
new file mode 100644
index 0000000..17acc59
--- /dev/null
+++ b/net/base/big_endian.cc
@@ -0,0 +1,98 @@
+// 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/base/big_endian.h"
+
+#include "base/string_piece.h"
+
+namespace net {
+
+BigEndianReader::BigEndianReader(const void* buf, size_t len)
+    : ptr_(reinterpret_cast<const char*>(buf)), end_(ptr_ + len) {}
+
+bool BigEndianReader::Skip(size_t len) {
+  if (ptr_ + len > end_)
+    return false;
+  ptr_ += len;
+  return true;
+}
+
+bool BigEndianReader::ReadBytes(void* out, size_t len) {
+  if (ptr_ + len > end_)
+    return false;
+  memcpy(out, ptr_, len);
+  ptr_ += len;
+  return true;
+}
+
+bool BigEndianReader::ReadPiece(base::StringPiece* out, size_t len) {
+  if (ptr_ + len > end_)
+    return false;
+  *out = base::StringPiece(ptr_, len);
+  ptr_ += len;
+  return true;
+}
+
+template<typename T>
+bool BigEndianReader::Read(T* value) {
+  if (ptr_ + sizeof(T) > end_)
+    return false;
+  ReadBigEndian<T>(ptr_, value);
+  ptr_ += sizeof(T);
+  return true;
+}
+
+bool BigEndianReader::ReadU8(uint8* value) {
+  return Read(value);
+}
+
+bool BigEndianReader::ReadU16(uint16* value) {
+  return Read(value);
+}
+
+bool BigEndianReader::ReadU32(uint32* value) {
+  return Read(value);
+}
+
+BigEndianWriter::BigEndianWriter(void* buf, size_t len)
+    : ptr_(reinterpret_cast<char*>(buf)), end_(ptr_ + len) {}
+
+bool BigEndianWriter::Skip(size_t len) {
+  if (ptr_ + len > end_)
+    return false;
+  ptr_ += len;
+  return true;
+}
+
+bool BigEndianWriter::WriteBytes(const void* buf, size_t len) {
+  if (ptr_ + len > end_)
+    return false;
+  memcpy(ptr_, buf, len);
+  ptr_ += len;
+  return true;
+}
+
+template<typename T>
+bool BigEndianWriter::Write(T value) {
+  if (ptr_ + sizeof(T) > end_)
+    return false;
+  WriteBigEndian<T>(ptr_, value);
+  ptr_ += sizeof(T);
+  return true;
+}
+
+bool BigEndianWriter::WriteU8(uint8 value) {
+  return Write(value);
+}
+
+bool BigEndianWriter::WriteU16(uint16 value) {
+  return Write(value);
+}
+
+bool BigEndianWriter::WriteU32(uint32 value) {
+  return Write(value);
+}
+
+}  // namespace net
+