Add QuicFramer and friends.

net/quic/quic_data_writer.cc

Index: net/quic/quic_data_writer.cc
diff --git a/net/quic/quic_data_writer.cc b/net/quic/quic_data_writer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4640ea16cbecb14e57a6f71284746ee239d6e4ea
--- /dev/null
+++ b/net/quic/quic_data_writer.cc
@@ -0,0 +1,69 @@
+// Copyright (c) 2012 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/quic/quic_data_writer.h"
+
+#include <algorithm>
+#include <limits>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "net/quic/quic_protocol.h"
+
+using std::numeric_limits;
+
+namespace net {
+
+QuicDataWriter::QuicDataWriter(size_t size)
+    : buffer_(new char[size]),
+      capacity_(size),
+      length_(0) {
+}
+
+QuicDataWriter::~QuicDataWriter() {
+  delete[] buffer_;
+}
+
+char* QuicDataWriter::BeginWrite(size_t length) {
+  if (length_ + length > capacity_) {

[jar (doing other things), 2012/10/16 19:24:01]

nit: To avoid integer overflow confusion, I think you really need to do this
test as:

if (capacity_ - length_ < length)

That approach trusts the slots to be reasonable, but then can handle any value
of |length|.

[Ryan Hamilton, 2012/10/16 19:43:23]

Ah, I see.  I didn't realize that was why you wrote the code that way (which
seemed convoluted.  Turns out it was ... for a reason).  Done.

+    return NULL;
+  }
+
+#ifdef ARCH_CPU_64_BITS
+  DCHECK_LE(length, numeric_limits<uint32>::max());
+#endif
+
+  return buffer_ + length_;
+}
+
+bool QuicDataWriter::AdvancePointer(uint32 len) {
+  if (!BeginWrite(len)) {
+    return false;
+  }
+  length_ += len;
+  return true;
+}
+
+bool QuicDataWriter::WriteBytes(const void* data, uint32 data_len) {
+  char* dest = BeginWrite(data_len);
+  if (!dest) {
+    return false;
+  }
+
+  memcpy(dest, data, data_len);
+
+  length_ += data_len;
+  return true;
+}
+
+void QuicDataWriter::WriteUint64ToBuffer(uint64 value, char* buffer) {
+  memcpy(buffer, &value, sizeof(value));
+}
+
+void QuicDataWriter::WriteUint128ToBuffer(uint128 value, char* buffer) {
+  WriteUint64ToBuffer(value.lo, buffer);
+  WriteUint64ToBuffer(value.hi, buffer + sizeof(value.lo));
+}
+
+}  // namespace net