Add data pipe wrappers to be used to implement serial receive.

device/serial/data_pipe_receiver.cc

+// 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 "device/serial/data_pipe_receiver.h"
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "device/serial/async_waiter.h"
+
+namespace device {
+
+class DataPipeReceiver::Buffer : public ReadOnlyBuffer {
+ public:
+  Buffer(scoped_refptr<DataPipeReceiver> pipe,
+         const char* buffer,
+         uint32_t buffer_size);
+  virtual ~Buffer();
+  virtual const char* GetData() OVERRIDE;
+  virtual uint32_t GetSize() OVERRIDE;
+  virtual void Done(uint32_t bytes_consumed) OVERRIDE;
+  virtual void DoneWithError(uint32_t bytes_consumed, int32_t error) OVERRIDE;
+
+ private:
+  scoped_refptr<DataPipeReceiver> pipe_;
+  const char* buffer_;
+  uint32_t buffer_size_;
+};
+
+DataPipeReceiver::DataPipeReceiver(
+    mojo::InterfacePtr<serial::DataPipeProducer> producer,
+    uint32_t buffer_size,
+    int32_t connection_error_value)
+    : producer_(producer.Pass()),
+      connection_error_value_(connection_error_value),
+      bytes_since_last_error_(0),
+      pending_error_(false),
+      error_offset_(0),
+      error_(0),
+      state_(STATE_IDLE),
+      weak_factory_(this) {
+  MojoCreateDataPipeOptions options = {
+      sizeof(options), MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE, 1, buffer_size,
+  };
+  options.struct_size = sizeof(options);

[raymes, 2014/08/05 06:26:44]

is this necessary?

[Sam McNally, 2014/08/05 07:26:33]

Yes.

+  mojo::ScopedDataPipeProducerHandle remote_handle;
+  MojoResult result = mojo::CreateDataPipe(&options, &remote_handle, &handle_);
+  DCHECK_EQ(MOJO_RESULT_OK, result);
+  producer_->Init(remote_handle.Pass());
+  producer_.set_client(this);
+}
+
+bool DataPipeReceiver::Receive(const ReceiveDataCallback& callback,
+                               const ReceiveErrorCallback& error_callback) {

[raymes, 2014/08/05 06:26:44]

Similarly for these functions it would be good to DCHECK that we are in one of
the valid states at the entrypoint to each function.

[Sam McNally, 2014/08/05 07:26:33]

Done.

+  if (state_ == STATE_PAUSED) {
+    producer_->Resume();
+    state_ = STATE_IDLE;
+  }
+  if (state_ != STATE_IDLE || callback.is_null() || error_callback.is_null()) {

[raymes, 2014/08/05 06:26:44]

Might as well just DCHECK null callbacks rather than have this test?
Also no need for {}

[Sam McNally, 2014/08/05 07:26:33]

Done.

+    return false;
+  }
+  state_ = STATE_WAITING_FOR_DATA;
+  receive_callback_ = callback;
+  receive_error_callback_ = error_callback;
+  base::MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&DataPipeReceiver::ReceiveInternal,
+                 weak_factory_.GetWeakPtr()));
+  return true;
+}
+
+DataPipeReceiver::~DataPipeReceiver() {
+  if (!receive_error_callback_.is_null())
+    DispatchError(connection_error_value_);
+}
+
+void DataPipeReceiver::Done(uint32_t bytes_consumed) {
+  if (state_ == STATE_SHUT_DOWN)
+    return;
+
+  MojoResult result = mojo::EndReadDataRaw(handle_.get(), bytes_consumed);
+  DCHECK_EQ(MOJO_RESULT_OK, result);
+  bytes_since_last_error_ += bytes_consumed;
+  state_ = STATE_IDLE;
+}
+
+void DataPipeReceiver::OnDoneWaiting(MojoResult result) {
+  RetryReceive();
+}
+
+void DataPipeReceiver::OnError(uint32_t bytes_since_last_error, int32_t error) {
+  pending_error_ = true;
+  error_ = error;
+  error_offset_ = bytes_since_last_error;
+  RetryReceive();
+}
+
+void DataPipeReceiver::OnConnectionError() {
+  state_ = STATE_SHUT_DOWN;
+  if (!receive_callback_.is_null())
+    DispatchError(connection_error_value_);
+}
+
+void DataPipeReceiver::RetryReceive() {
+  if (!receive_callback_.is_null())
+    ReceiveInternal();
+}
+
+void DataPipeReceiver::ReceiveInternal() {
+  if (pending_error_ && bytes_since_last_error_ >= error_offset_) {
+    pending_error_ = false;
+    bytes_since_last_error_ -= error_offset_;
+    error_offset_ = 0;
+    state_ = STATE_PAUSED;
+    DispatchError(error_);
+    return;
+  }
+  const void* data;
+  uint32_t num_bytes = std::numeric_limits<uint32_t>::max();
+  MojoResult result = mojo::BeginReadDataRaw(
+      handle_.get(), &data, &num_bytes, MOJO_READ_DATA_FLAG_NONE);
+  switch (result) {

[raymes, 2014/08/05 06:26:44]

consider just using if/else rather than switch since we're only ever considering
2 cases

[Sam McNally, 2014/08/05 07:26:33]

Done.

+    case MOJO_RESULT_OK:
+      DispatchData(data, num_bytes);
+      break;
+    case MOJO_RESULT_SHOULD_WAIT:
+      waiter_.reset(new AsyncWaiter(handle_.get(),
+                                    MOJO_HANDLE_SIGNAL_READABLE,
+                                    base::Bind(&DataPipeReceiver::OnDoneWaiting,

[raymes, 2014/08/05 06:26:44]

Could you bind directly to RetryReceive?

[Sam McNally, 2014/08/05 07:26:33]

OnDoneWaiting should be doing something with the wait result.

+                                               weak_factory_.GetWeakPtr())));
+      break;
+    default:
+      state_ = STATE_SHUT_DOWN;
+      DispatchError(connection_error_value_);
+      break;
+  }
+}
+
+void DataPipeReceiver::DispatchData(const void* data, uint32_t num_bytes) {
+  state_ = STATE_WAITING_FOR_BUFFER;
+  ReceiveDataCallback callback = receive_callback_;
+  receive_callback_.Reset();
+  receive_error_callback_.Reset();
+  callback.Run(scoped_ptr<ReadOnlyBuffer>(
+      new Buffer(this, static_cast<const char*>(data), num_bytes)));
+}
+
+void DataPipeReceiver::DispatchError(int32_t error) {
+  if (state_ == STATE_WAITING_FOR_DATA)
+    state_ = STATE_IDLE;
+  ReceiveErrorCallback callback = receive_error_callback_;
+  receive_callback_.Reset();
+  receive_error_callback_.Reset();
+  callback.Run(error);
+}
+
+DataPipeReceiver::Buffer::Buffer(scoped_refptr<DataPipeReceiver> pipe,
+                                 const char* buffer,
+                                 uint32_t buffer_size)
+    : pipe_(pipe), buffer_(buffer), buffer_size_(buffer_size) {
+}
+
+DataPipeReceiver::Buffer::~Buffer() {
+  if (pipe_)
+    pipe_->Done(0);
+}
+
+const char* DataPipeReceiver::Buffer::GetData() {
+  return buffer_;
+}
+
+uint32_t DataPipeReceiver::Buffer::GetSize() {
+  return buffer_size_;
+}
+
+void DataPipeReceiver::Buffer::Done(uint32_t bytes_consumed) {
+  pipe_->Done(bytes_consumed);
+  pipe_ = NULL;
+  buffer_ = NULL;
+  buffer_size_ = 0;
+}
+
+void DataPipeReceiver::Buffer::DoneWithError(uint32_t bytes_consumed,
+                                             int32_t error) {
+  Done(bytes_consumed);
+}
+
+}  // namespace device