Add ProtoDecoder for sending messages between Host and Controller when pairing

components/pairing/proto_decoder.cc

Index: components/pairing/proto_decoder.cc
diff --git a/components/pairing/proto_decoder.cc b/components/pairing/proto_decoder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..96b3c24feb7a804f946887fdbc1e8ebcb72f554a
--- /dev/null
+++ b/components/pairing/proto_decoder.cc
@@ -0,0 +1,201 @@
+// Copyright 2014 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 "components/pairing/proto_decoder.h"
+
+#include "components/pairing/pairing_api.pb.h"
+#include "net/base/io_buffer.h"
+
+namespace {
+enum {
+  MESSAGE_NONE,
+  MESSAGE_HOST_STATUS,
+  MESSAGE_CONFIGURE_HOST,
+  MESSAGE_PAIR_DEVICES,
+  MESSAGE_COMPLETE_SETUP,
+  MESSAGE_ERROR,
+  NUM_MESSAGES,
+};
+}
+
+namespace pairing_chromeos {
+
+ProtoDecoder::ProtoDecoder(Observer* observer)
+    : observer_(observer),
+      next_message_type_(MESSAGE_NONE),
+      next_message_size_(0) {
+  DCHECK(observer_);
+}
+
+ProtoDecoder::~ProtoDecoder() {}
+
+bool ProtoDecoder::DecodeIOBuffer(int size,
+                                  ProtoDecoder::IOBufferRefPtr io_buffer) {
+  // Update the message buffer.
+  message_buffer_.AddIOBuffer(io_buffer, size);
+
+  // If there is no current message, the next byte is the message type.
+  if (next_message_type_ == MESSAGE_NONE) {
+    if (message_buffer_.AvailableBytes() < static_cast<int>(sizeof(uint8_t)))
+      return true;
+
+    uint8_t message_type = MESSAGE_NONE;
+    message_buffer_.ReadBytes(reinterpret_cast<char*>(&message_type),
+                               sizeof(message_type));
+
+    if (message_type == MESSAGE_NONE || message_type >= NUM_MESSAGES) {
+      LOG(ERROR) << "Unknown message type received: " << message_type;
+      return false;
+    }
+    next_message_type_ = message_type;
+  }
+
+  // If the message size isn't set, the next two bytes are the message size.
+  if (next_message_size_ == 0) {
+    if (message_buffer_.AvailableBytes() < static_cast<int>(sizeof(uint16_t)))
+      return true;
+
+    // The size is sent in network byte order.
+    uint8_t high_byte = 0;
+    message_buffer_.ReadBytes(reinterpret_cast<char*>(&high_byte),
+                               sizeof(high_byte));
+    uint8_t low_byte = 0;
+    message_buffer_.ReadBytes(reinterpret_cast<char*>(&low_byte),
+                               sizeof(low_byte));
+
+    next_message_size_ = (high_byte << 8) + low_byte;
+  }
+
+  // If the whole proto buffer is not yet available, return early.
+  if (message_buffer_.AvailableBytes() < next_message_size_)
+    return true;
+
+  std::vector<char> buffer(next_message_size_);
+  message_buffer_.ReadBytes(&buffer[0], next_message_size_);
+
+  switch (next_message_type_) {
+    case MESSAGE_HOST_STATUS: {
+        pairing_api::HostStatus message;
+        message.ParseFromArray(&buffer[0], buffer.size());
+        observer_->OnHostStatusMessage(message);
+      }
+      break;
+    case MESSAGE_CONFIGURE_HOST: {
+        pairing_api::ConfigureHost message;
+        message.ParseFromArray(&buffer[0], buffer.size());
+        observer_->OnConfigureHostMessage(message);
+      }
+      break;
+    case MESSAGE_PAIR_DEVICES: {
+        pairing_api::PairDevices message;
+        message.ParseFromArray(&buffer[0], buffer.size());
+        observer_->OnPairDevicesMessage(message);
+      }
+      break;
+    case MESSAGE_COMPLETE_SETUP: {
+        pairing_api::CompleteSetup message;
+        message.ParseFromArray(&buffer[0], buffer.size());
+        observer_->OnCompleteSetupMessage(message);
+      }
+      break;
+    case MESSAGE_ERROR: {
+        pairing_api::Error message;
+        message.ParseFromArray(&buffer[0], buffer.size());
+        observer_->OnErrorMessage(message);
+      }
+      break;
+
+    default:
+      NOTREACHED();
+      break;
+  }
+
+  // Reset the message data.
+  next_message_type_ = MESSAGE_NONE;
+  next_message_size_ = 0;
+
+  return true;
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendHostStatus(
+    const pairing_api::HostStatus& message, int* size) {
+  std::string serialized_proto;
+  if (!message.SerializeToString(&serialized_proto)) {
+    NOTREACHED();
+  }
+
+  return SendMessage(MESSAGE_HOST_STATUS, serialized_proto, size);
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendConfigureHost(
+    const pairing_api::ConfigureHost& message, int* size) {
+  std::string serialized_proto;
+  if (!message.SerializeToString(&serialized_proto)) {
+    NOTREACHED();
+  }
+
+  return SendMessage(MESSAGE_CONFIGURE_HOST, serialized_proto, size);
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendPairDevices(
+    const pairing_api::PairDevices& message, int* size) {
+  std::string serialized_proto;
+  if (!message.SerializeToString(&serialized_proto)) {
+    NOTREACHED();
+  }
+
+  return SendMessage(MESSAGE_PAIR_DEVICES, serialized_proto, size);
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendCompleteSetup(
+    const pairing_api::CompleteSetup& message, int* size) {
+  std::string serialized_proto;
+  if (!message.SerializeToString(&serialized_proto)) {
+    NOTREACHED();
+  }
+
+  return SendMessage(MESSAGE_COMPLETE_SETUP, serialized_proto, size);
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendError(
+    const pairing_api::Error& message, int* size) {
+  std::string serialized_proto;
+  if (!message.SerializeToString(&serialized_proto)) {
+    NOTREACHED();
+  }
+
+  return SendMessage(MESSAGE_ERROR, serialized_proto, size);
+}
+
+ProtoDecoder::IOBufferRefPtr ProtoDecoder::SendMessage(
+    uint8_t message_type,
+    const std::string& message,
+    int* size) {
+  uint16_t message_size = message.size();
+
+  *size = sizeof(message_type) + sizeof(message_size) + message.size();
+  IOBufferRefPtr io_buffer(new net::IOBuffer(*size));
+
+  // Write the message type.
+  int offset = 0;
+  memcpy(&io_buffer->data()[offset], &message_type, sizeof(message_type));
+  offset += sizeof(message_type);
+
+  // Network byte order.
+  // Write the high byte of the size.
+  uint8_t data = (message_size >> 8) & 0xFF;
+  memcpy(&io_buffer->data()[offset], &data, sizeof(data));
+  offset += sizeof(data);
+  // Write the low byte of the size.
+  data = message_size & 0xFF;
+  memcpy(&io_buffer->data()[offset], &data, sizeof(data));
+  offset += sizeof(data);
+
+  // Write the actual message.
+  memcpy(&io_buffer->data()[offset], message.data(), message.size());
+
+  return io_buffer;
+}
+
+}  // namespace pairing_chromeos