Add framing for CastMessage

This change imports cast_framer.cc from Chromium's
//components/cast_channel.

Bug: openscreen:59
Change-Id: I189b6d1a243f439c8e8585afdb94f4bdd3d62251
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/1775425
Commit-Queue: Brandon Tolsch <btolsch@chromium.org>
Reviewed-by: Max Yakimakha <yakimakha@chromium.org>
Reviewed-by: Ryan Keane <rwkeane@google.com>

1 files changed, 94 insertions, 0 deletions

diff --git a/cast/sender/channel/cast_framer.cc b/cast/sender/channel/cast_framer.cc
new file mode 100644
index 00000000..b5a8acb1
--- /dev/null
+++ b/cast/sender/channel/cast_framer.cc
@@ -0,0 +1,94 @@
+// Copyright 2019 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 "cast/sender/channel/cast_framer.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <limits>
+
+#include "cast/sender/channel/proto/cast_channel.pb.h"
+#include "platform/api/logging.h"
+#include "util/big_endian.h"
+#include "util/std_util.h"
+
+namespace cast {
+namespace channel {
+
+using ChannelError = openscreen::Error::Code;
+
+namespace {
+
+static constexpr size_t kHeaderSize = sizeof(uint32_t);
+
+// Cast specifies a max message body size of 64 KiB.
+static constexpr size_t kMaxBodySize = 65536;
+
+}  // namespace
+
+MessageFramer::MessageFramer(absl::Span<uint8_t> input_buffer)
+    : input_buffer_(input_buffer) {}
+
+MessageFramer::~MessageFramer() = default;
+
+// static
+ErrorOr<std::string> MessageFramer::Serialize(const CastMessage& message) {
+  const size_t message_size = message.ByteSizeLong();
+  if (message_size > kMaxBodySize || message_size == 0) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+  std::string out(message_size + kHeaderSize, 0);
+  openscreen::WriteBigEndian<uint32_t>(message_size, openscreen::data(out));
+  if (!message.SerializeToArray(&out[kHeaderSize], message_size)) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+  return out;
+}
+
+ErrorOr<size_t> MessageFramer::BytesRequested() const {
+  if (message_bytes_received_ < kHeaderSize) {
+    return kHeaderSize - message_bytes_received_;
+  }
+
+  const uint32_t message_size =
+      openscreen::ReadBigEndian<uint32_t>(input_buffer_.data());
+  if (message_size > kMaxBodySize) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+  return (kHeaderSize + message_size) - message_bytes_received_;
+}
+
+ErrorOr<CastMessage> MessageFramer::TryDeserialize(size_t byte_count) {
+  message_bytes_received_ += byte_count;
+  if (message_bytes_received_ > input_buffer_.size()) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+
+  if (message_bytes_received_ < kHeaderSize) {
+    return ChannelError::kInsufficientBuffer;
+  }
+
+  const uint32_t message_size =
+      openscreen::ReadBigEndian<uint32_t>(input_buffer_.data());
+  if (message_size > kMaxBodySize) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+
+  if (message_bytes_received_ < (kHeaderSize + message_size)) {
+    return ChannelError::kInsufficientBuffer;
+  }
+
+  CastMessage parsed_message;
+  if (!parsed_message.ParseFromArray(input_buffer_.data() + kHeaderSize,
+                                     message_size)) {
+    return ChannelError::kCastV2InvalidMessage;
+  }
+
+  message_bytes_received_ = 0;
+  return parsed_message;
+}
+
+}  // namespace channel
+}  // namespace cast