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

device/serial/data_source_sender.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_source_sender.h"
+
+#include <limits>
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "device/serial/async_waiter.h"
+
+namespace device {
+
+class DataSourceSender::PendingSend {
+ public:
+  PendingSend(DataSourceSender* sender, const ReadyCallback& callback);
+  void GetData(void* data, uint32_t num_bytes);
+
+ private:
+  class Buffer;
+  void Done(uint32_t bytes_produced);
+  void DoneWithError(uint32_t bytes_produced, int32_t error);
+
+  DataSourceSender* sender_;
+  ReadyCallback callback_;
+  bool buffer_in_use_;
+};
+
+class DataSourceSender::PendingSend::Buffer : public WritableBuffer {
+ public:
+  Buffer(scoped_refptr<DataSourceSender> sender,
+         PendingSend* send,
+         char* buffer,
+         uint32_t buffer_size);
+  virtual ~Buffer();
+  virtual char* GetData() OVERRIDE;
+  virtual uint32_t GetSize() OVERRIDE;
+  virtual void Done(uint32_t bytes_produced) OVERRIDE;
+  virtual void DoneWithError(uint32_t bytes_produced, int32_t error) OVERRIDE;
+
+ private:
+  scoped_refptr<DataSourceSender> sender_;
+  PendingSend* send_;
+  char* buffer_;
+  uint32_t buffer_size_;
+};
+
+DataSourceSender::DataSourceSender(const ReadyCallback& ready_callback,
+                                   const ErrorCallback& error_callback)
+    : ready_callback_(ready_callback),
+      error_callback_(error_callback),
+      bytes_sent_(0),
+      shut_down_(false) {
+  DCHECK(!ready_callback.is_null() && !error_callback.is_null());
+}
+
+void DataSourceSender::ShutDown() {
+  shut_down_ = true;
+  waiter_.reset();

[raymes, 2014/08/06 06:41:53]

I guess we could reset send_ here too?
Also consider resetting the callbacks to ensure we never run them again.

[Sam McNally, 2014/08/06 08:28:14]

We can't reset pending_send_ in case it has buffer_in_use_

+}
+
+DataSourceSender::~DataSourceSender() {
+  DCHECK(shut_down_);
+}
+
+void DataSourceSender::Init(mojo::ScopedDataPipeProducerHandle handle) {
+  if (send_ || handle_.is_valid())

[raymes, 2014/08/06 06:41:53]

send_ -> pending_send_

I guess this case should never happen under normal operation, should we
shutdown? A comment explaining this could be good.

[Sam McNally, 2014/08/06 08:28:14]

Done.

+    return;
+
+  handle_ = handle.Pass();
+  send_.reset(new PendingSend(this, ready_callback_));
+  StartWaiting();
+}
+
+void DataSourceSender::Resume() {
+  if (send_ || !handle_.is_valid())

[raymes, 2014/08/06 06:41:53]

-Can the handle_ ever go from being valid to invalid during operation? Can we
just test this once in Init()?

-Similarly in this case we can probably shut down here because this isn't
expected under normal operation.

[Sam McNally, 2014/08/06 08:28:14]

It could get called before Init().

+    return;
+
+  send_.reset(new PendingSend(this, ready_callback_));
+  StartWaiting();
+}
+
+void DataSourceSender::OnConnectionError() {
+  DispatchFatalError();
+}
+
+void DataSourceSender::StartWaiting() {
+  DCHECK(send_);

[raymes, 2014/08/06 06:41:53]

Also !waiter_ should be true here?

[Sam McNally, 2014/08/06 08:28:14]

Done.

+  waiter_.reset(
+      new AsyncWaiter(handle_.get(),
+                      MOJO_HANDLE_SIGNAL_WRITABLE,
+                      base::Bind(&DataSourceSender::OnDoneWaiting, this)));
+}
+
+void DataSourceSender::OnDoneWaiting(MojoResult result) {
+  DCHECK(send_ && !shut_down_);
+  if (!HandleMojoResult(result))
+    return;

[raymes, 2014/08/06 06:41:53]

I think you can get rid of the HandleMojoResult function and it's not much more
verbose. We already DCHECK send_ at all the call sites, so it boils down to:

if (result != MOJO_RESULT_OK)
  DispatchFatalError();
  return;
}

[Sam McNally, 2014/08/06 08:28:14]

Done.

+  void* data = NULL;
+  uint32_t num_bytes = std::numeric_limits<uint32_t>::max();
+  result = mojo::BeginWriteDataRaw(
+      handle_.get(), &data, &num_bytes, MOJO_READ_DATA_FLAG_NONE);
+  if (!HandleMojoResult(result))
+    return;
+  send_->GetData(static_cast<char*>(data), num_bytes);
+}
+
+void DataSourceSender::Done(uint32_t bytes_produced) {
+  DoneInternal(bytes_produced);
+  if (!shut_down_)
+    StartWaiting();
+}
+
+void DataSourceSender::DoneWithError(uint32_t bytes_produced, int32_t error) {

[raymes, 2014/08/06 06:41:53]

Make a note in here that we don't call StartWaiting intentionally so that we
don't send any additional data until Resume() is called.

[Sam McNally, 2014/08/06 08:28:15]

Done.

+  DoneInternal(bytes_produced);
+  send_.reset();
+  if (!shut_down_)
+    client()->OnError(bytes_sent_, error);
+}
+
+void DataSourceSender::DoneInternal(uint32_t bytes_produced) {

[raymes, 2014/08/06 06:41:53]

Should we bail if we are shut_down_ on entry to this function?

[Sam McNally, 2014/08/06 08:28:15]

Done.

+  DCHECK(send_);
+  bytes_sent_ += bytes_produced;
+  MojoResult result = mojo::EndWriteDataRaw(handle_.get(), bytes_produced);
+  if (!HandleMojoResult(result))
+    return;
+}
+
+bool DataSourceSender::HandleMojoResult(MojoResult result) {
+  DCHECK(send_);
+  if (result == MOJO_RESULT_OK)
+    return true;
+  DispatchFatalError();
+  return false;
+}
+
+void DataSourceSender::DispatchFatalError() {
+  if (shut_down_)
+    return;
+
+  ShutDown();
+  error_callback_.Run();
+}
+
+DataSourceSender::PendingSend::PendingSend(DataSourceSender* sender,
+                                           const ReadyCallback& callback)
+    : sender_(sender), callback_(callback), buffer_in_use_(false) {
+}
+
+void DataSourceSender::PendingSend::GetData(void* data, uint32_t num_bytes) {
+  DCHECK(!buffer_in_use_);
+  buffer_in_use_ = true;
+  callback_.Run(scoped_ptr<WritableBuffer>(
+      new Buffer(sender_, this, static_cast<char*>(data), num_bytes)));
+}
+
+void DataSourceSender::PendingSend::Done(uint32_t bytes_produced) {
+  DCHECK(buffer_in_use_);
+  buffer_in_use_ = false;
+  sender_->Done(bytes_produced);
+}
+
+void DataSourceSender::PendingSend::DoneWithError(uint32_t bytes_produced,
+                                                  int32_t error) {
+  DCHECK(buffer_in_use_);
+  buffer_in_use_ = false;
+  sender_->DoneWithError(bytes_produced, error);
+}
+
+DataSourceSender::PendingSend::Buffer::Buffer(
+    scoped_refptr<DataSourceSender> sender,
+    PendingSend* send,
+    char* buffer,
+    uint32_t buffer_size)
+    : sender_(sender), send_(send), buffer_(buffer), buffer_size_(buffer_size) {
+}
+
+DataSourceSender::PendingSend::Buffer::~Buffer() {
+  if (sender_)
+    send_->Done(0);
+}
+
+char* DataSourceSender::PendingSend::Buffer::GetData() {
+  return buffer_;
+}
+
+uint32_t DataSourceSender::PendingSend::Buffer::GetSize() {
+  return buffer_size_;
+}
+
+void DataSourceSender::PendingSend::Buffer::Done(uint32_t bytes_produced) {
+  DCHECK(sender_);
+  send_->Done(bytes_produced);
+  sender_ = NULL;
+  send_ = NULL;
+  buffer_ = NULL;
+  buffer_size_ = 0;
+}
+
+void DataSourceSender::PendingSend::Buffer::DoneWithError(
+    uint32_t bytes_produced,
+    int32_t error) {
+  DCHECK(sender_);
+  send_->DoneWithError(bytes_produced, error);
+  sender_ = NULL;
+  send_ = NULL;
+  buffer_ = NULL;
+  buffer_size_ = 0;
+}
+
+}  // namespace device