mojo/edk/system/remote_producer_data_pipe_impl.cc - external/github.com/flutter/engine - Git at Google

 // Copyright 2015 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 "mojo/edk/system/remote_producer_data_pipe_impl.h"

 #include <string.h>

 #include <algorithm>

 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "mojo/edk/system/channel.h"
 #include "mojo/edk/system/channel_endpoint.h"
 #include "mojo/edk/system/configuration.h"
 #include "mojo/edk/system/data_pipe.h"
 #include "mojo/edk/system/message_in_transit.h"
 #include "mojo/edk/system/message_in_transit_queue.h"
 #include "mojo/edk/system/remote_consumer_data_pipe_impl.h"
 #include "mojo/edk/system/remote_data_pipe_ack.h"

 namespace mojo {
 namespace system {

 namespace {

 bool ValidateIncomingMessage(size_t element_num_bytes,
                              size_t capacity_num_bytes,
                              size_t current_num_bytes,
                              const MessageInTransit* message) {
   // We should only receive endpoint client messages.
   DCHECK_EQ(message->type(), MessageInTransit::Type::ENDPOINT_CLIENT);

   // But we should check the subtype; only take data messages.
   if (message->subtype() != MessageInTransit::Subtype::ENDPOINT_CLIENT_DATA) {
     LOG(WARNING) << "Received message of unexpected subtype: "
                  << message->subtype();
     return false;
   }

   const size_t num_bytes = message->num_bytes();
   const size_t max_num_bytes = capacity_num_bytes - current_num_bytes;
   if (num_bytes > max_num_bytes) {
     LOG(WARNING) << "Received too much data: " << num_bytes
                  << " bytes (maximum: " << max_num_bytes << " bytes)";
     return false;
   }

   if (num_bytes % element_num_bytes != 0) {
     LOG(WARNING) << "Received data not a multiple of element size: "
                  << num_bytes << " bytes (element size: " << element_num_bytes
                  << " bytes)";
     return false;
   }

   return true;
 }

 }  // namespace

 RemoteProducerDataPipeImpl::RemoteProducerDataPipeImpl(
     ChannelEndpoint* channel_endpoint)
     : channel_endpoint_(channel_endpoint),
       start_index_(0),
       current_num_bytes_(0) {
   // Note: |buffer_| is lazily allocated.
 }

 RemoteProducerDataPipeImpl::RemoteProducerDataPipeImpl(
     ChannelEndpoint* channel_endpoint,
     scoped_ptr<char, base::AlignedFreeDeleter> buffer,
     size_t start_index,
     size_t current_num_bytes)
     : channel_endpoint_(channel_endpoint),
       buffer_(buffer.Pass()),
       start_index_(start_index),
       current_num_bytes_(current_num_bytes) {
   DCHECK(buffer_ || !current_num_bytes);
 }

 // static
 bool RemoteProducerDataPipeImpl::ProcessMessagesFromIncomingEndpoint(
     const MojoCreateDataPipeOptions& validated_options,
     MessageInTransitQueue* messages,
     scoped_ptr<char, base::AlignedFreeDeleter>* buffer,
     size_t* buffer_num_bytes) {
   DCHECK(!*buffer);  // Not wrong, but unlikely.

   const size_t element_num_bytes = validated_options.element_num_bytes;
   const size_t capacity_num_bytes = validated_options.capacity_num_bytes;

   scoped_ptr<char, base::AlignedFreeDeleter> new_buffer(static_cast<char*>(
       base::AlignedAlloc(capacity_num_bytes,
                          GetConfiguration().data_pipe_buffer_alignment_bytes)));

   size_t current_num_bytes = 0;
   if (messages) {
     while (!messages->IsEmpty()) {
       scoped_ptr<MessageInTransit> message(messages->GetMessage());
       if (!ValidateIncomingMessage(element_num_bytes, capacity_num_bytes,
                                    current_num_bytes, message.get())) {
         messages->Clear();
         return false;
       }

       memcpy(new_buffer.get() + current_num_bytes, message->bytes(),
              message->num_bytes());
       current_num_bytes += message->num_bytes();
     }
   }

   *buffer = new_buffer.Pass();
   *buffer_num_bytes = current_num_bytes;
   return true;
 }

 RemoteProducerDataPipeImpl::~RemoteProducerDataPipeImpl() {
 }

 void RemoteProducerDataPipeImpl::ProducerClose() {
   NOTREACHED();
 }

 MojoResult RemoteProducerDataPipeImpl::ProducerWriteData(
     UserPointer<const void> /*elements*/,
     UserPointer<uint32_t> /*num_bytes*/,
     uint32_t /*max_num_bytes_to_write*/,
     uint32_t /*min_num_bytes_to_write*/) {
   NOTREACHED();
   return MOJO_RESULT_INTERNAL;
 }

 MojoResult RemoteProducerDataPipeImpl::ProducerBeginWriteData(
     UserPointer<void*> /*buffer*/,
     UserPointer<uint32_t> /*buffer_num_bytes*/,
     uint32_t /*min_num_bytes_to_write*/) {
   NOTREACHED();
   return MOJO_RESULT_INTERNAL;
 }

 MojoResult RemoteProducerDataPipeImpl::ProducerEndWriteData(
     uint32_t /*num_bytes_written*/) {
   NOTREACHED();
   return MOJO_RESULT_INTERNAL;
 }

 HandleSignalsState RemoteProducerDataPipeImpl::ProducerGetHandleSignalsState()
     const {
   return HandleSignalsState();
 }

 void RemoteProducerDataPipeImpl::ProducerStartSerialize(
     Channel* /*channel*/,
     size_t* /*max_size*/,
     size_t* /*max_platform_handles*/) {
   NOTREACHED();
 }

 bool RemoteProducerDataPipeImpl::ProducerEndSerialize(
     Channel* /*channel*/,
     void* /*destination*/,
     size_t* /*actual_size*/,
     embedder::PlatformHandleVector* /*platform_handles*/) {
   NOTREACHED();
   return false;
 }

 void RemoteProducerDataPipeImpl::ConsumerClose() {
   if (producer_open())
     Disconnect();
   current_num_bytes_ = 0;
 }

 MojoResult RemoteProducerDataPipeImpl::ConsumerReadData(
     UserPointer<void> elements,
     UserPointer<uint32_t> num_bytes,
     uint32_t max_num_bytes_to_read,
     uint32_t min_num_bytes_to_read,
     bool peek) {
   DCHECK_EQ(max_num_bytes_to_read % element_num_bytes(), 0u);
   DCHECK_EQ(min_num_bytes_to_read % element_num_bytes(), 0u);
   DCHECK_GT(max_num_bytes_to_read, 0u);

   if (min_num_bytes_to_read > current_num_bytes_) {
     // Don't return "should wait" since you can't wait for a specified amount of
     // data.
     return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   size_t num_bytes_to_read =
       std::min(static_cast<size_t>(max_num_bytes_to_read), current_num_bytes_);
   if (num_bytes_to_read == 0) {
     return producer_open() ? MOJO_RESULT_SHOULD_WAIT
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   // The amount we can read in our first |memcpy()|.
   size_t num_bytes_to_read_first =
       std::min(num_bytes_to_read, GetMaxNumBytesToRead());
   elements.PutArray(buffer_.get() + start_index_, num_bytes_to_read_first);

   if (num_bytes_to_read_first < num_bytes_to_read) {
     // The "second read index" is zero.
     elements.At(num_bytes_to_read_first)
         .PutArray(buffer_.get(), num_bytes_to_read - num_bytes_to_read_first);
   }

   if (!peek)
     MarkDataAsConsumed(num_bytes_to_read);
   num_bytes.Put(static_cast<uint32_t>(num_bytes_to_read));
   return MOJO_RESULT_OK;
 }

 MojoResult RemoteProducerDataPipeImpl::ConsumerDiscardData(
     UserPointer<uint32_t> num_bytes,
     uint32_t max_num_bytes_to_discard,
     uint32_t min_num_bytes_to_discard) {
   DCHECK_EQ(max_num_bytes_to_discard % element_num_bytes(), 0u);
   DCHECK_EQ(min_num_bytes_to_discard % element_num_bytes(), 0u);
   DCHECK_GT(max_num_bytes_to_discard, 0u);

   if (min_num_bytes_to_discard > current_num_bytes_) {
     // Don't return "should wait" since you can't wait for a specified amount of
     // data.
     return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   // Be consistent with other operations; error if no data available.
   if (current_num_bytes_ == 0) {
     return producer_open() ? MOJO_RESULT_SHOULD_WAIT
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   size_t num_bytes_to_discard = std::min(
       static_cast<size_t>(max_num_bytes_to_discard), current_num_bytes_);
   MarkDataAsConsumed(num_bytes_to_discard);
   num_bytes.Put(static_cast<uint32_t>(num_bytes_to_discard));
   return MOJO_RESULT_OK;
 }

 MojoResult RemoteProducerDataPipeImpl::ConsumerQueryData(
     UserPointer<uint32_t> num_bytes) {
   // Note: This cast is safe, since the capacity fits into a |uint32_t|.
   num_bytes.Put(static_cast<uint32_t>(current_num_bytes_));
   return MOJO_RESULT_OK;
 }

 MojoResult RemoteProducerDataPipeImpl::ConsumerBeginReadData(
     UserPointer<const void*> buffer,
     UserPointer<uint32_t> buffer_num_bytes,
     uint32_t min_num_bytes_to_read) {
   size_t max_num_bytes_to_read = GetMaxNumBytesToRead();
   if (min_num_bytes_to_read > max_num_bytes_to_read) {
     // Don't return "should wait" since you can't wait for a specified amount of
     // data.
     return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   // Don't go into a two-phase read if there's no data.
   if (max_num_bytes_to_read == 0) {
     return producer_open() ? MOJO_RESULT_SHOULD_WAIT
                            : MOJO_RESULT_FAILED_PRECONDITION;
   }

   buffer.Put(buffer_.get() + start_index_);
   buffer_num_bytes.Put(static_cast<uint32_t>(max_num_bytes_to_read));
   set_consumer_two_phase_max_num_bytes_read(
       static_cast<uint32_t>(max_num_bytes_to_read));
   return MOJO_RESULT_OK;
 }

 MojoResult RemoteProducerDataPipeImpl::ConsumerEndReadData(
     uint32_t num_bytes_read) {
   DCHECK_LE(num_bytes_read, consumer_two_phase_max_num_bytes_read());
   DCHECK_EQ(num_bytes_read % element_num_bytes(), 0u);
   DCHECK_LE(start_index_ + num_bytes_read, capacity_num_bytes());
   MarkDataAsConsumed(num_bytes_read);
   set_consumer_two_phase_max_num_bytes_read(0);
   return MOJO_RESULT_OK;
 }

 HandleSignalsState RemoteProducerDataPipeImpl::ConsumerGetHandleSignalsState()
     const {
   HandleSignalsState rv;
   if (current_num_bytes_ > 0) {
     if (!consumer_in_two_phase_read())
       rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_READABLE;
     rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_READABLE;
   } else if (producer_open()) {
     rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_READABLE;
   }
   if (!producer_open())
     rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
   rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
   return rv;
 }

 void RemoteProducerDataPipeImpl::ConsumerStartSerialize(
     Channel* channel,
     size_t* max_size,
     size_t* max_platform_handles) {
   *max_size = sizeof(SerializedDataPipeConsumerDispatcher) +
               channel->GetSerializedEndpointSize();
   *max_platform_handles = 0;
 }

 bool RemoteProducerDataPipeImpl::ConsumerEndSerialize(
     Channel* channel,
     void* destination,
     size_t* actual_size,
     embedder::PlatformHandleVector* platform_handles) {
   SerializedDataPipeConsumerDispatcher* s =
       static_cast<SerializedDataPipeConsumerDispatcher*>(destination);
   s->validated_options = validated_options();
   void* destination_for_endpoint = static_cast<char*>(destination) +
                                    sizeof(SerializedDataPipeConsumerDispatcher);

   MessageInTransitQueue message_queue;
   ConvertDataToMessages(buffer_.get(), &start_index_, &current_num_bytes_,
                         &message_queue);

   if (!producer_open()) {
     // Case 1: The producer is closed.
     channel->SerializeEndpointWithClosedPeer(destination_for_endpoint,
                                              &message_queue);
     *actual_size = sizeof(SerializedDataPipeConsumerDispatcher) +
                    channel->GetSerializedEndpointSize();
     return true;
   }

   // Case 2: The producer isn't closed. We pass |channel_endpoint| back to the
   // |Channel|. There's no reason for us to continue to exist afterwards.

   // Note: We don't use |port|.
   scoped_refptr<ChannelEndpoint> channel_endpoint;
   channel_endpoint.swap(channel_endpoint_);
   channel->SerializeEndpointWithRemotePeer(destination_for_endpoint,
                                            &message_queue, channel_endpoint);
   owner()->SetProducerClosedNoLock();

   *actual_size = sizeof(SerializedDataPipeConsumerDispatcher) +
                  channel->GetSerializedEndpointSize();
   return true;
 }

 bool RemoteProducerDataPipeImpl::OnReadMessage(unsigned /*port*/,
                                                MessageInTransit* message) {
   if (!producer_open()) {
     // This will happen only on the rare occasion that the call to
     // |OnReadMessage()| is racing with us calling
     // |ChannelEndpoint::ReplaceClient()|, in which case we reject the message,
     // and the |ChannelEndpoint| can retry (calling the new client's
     // |OnReadMessage()|).
     DCHECK(!channel_endpoint_);
     return false;
   }

   // Otherwise, we take ownership of the message. (This means that we should
   // always return true below.)
   scoped_ptr<MessageInTransit> msg(message);

   if (!ValidateIncomingMessage(element_num_bytes(), capacity_num_bytes(),
                                current_num_bytes_, msg.get())) {
     Disconnect();
     return true;
   }

   size_t num_bytes = msg->num_bytes();
   // The amount we can write in our first copy.
   size_t num_bytes_to_copy_first = std::min(num_bytes, GetMaxNumBytesToWrite());
   // Do the first (and possibly only) copy.
   size_t first_write_index =
       (start_index_ + current_num_bytes_) % capacity_num_bytes();
   EnsureBuffer();
   memcpy(buffer_.get() + first_write_index, msg->bytes(),
          num_bytes_to_copy_first);

   if (num_bytes_to_copy_first < num_bytes) {
     // The "second write index" is zero.
     memcpy(buffer_.get(),
            static_cast<const char*>(msg->bytes()) + num_bytes_to_copy_first,
            num_bytes - num_bytes_to_copy_first);
   }

   current_num_bytes_ += num_bytes;
   DCHECK_LE(current_num_bytes_, capacity_num_bytes());
   return true;
 }

 void RemoteProducerDataPipeImpl::OnDetachFromChannel(unsigned /*port*/) {
   if (!producer_open()) {
     DCHECK(!channel_endpoint_);
     return;
   }

   Disconnect();
 }

 void RemoteProducerDataPipeImpl::EnsureBuffer() {
   DCHECK(producer_open());
   if (buffer_)
     return;
   buffer_.reset(static_cast<char*>(
       base::AlignedAlloc(capacity_num_bytes(),
                          GetConfiguration().data_pipe_buffer_alignment_bytes)));
 }

 void RemoteProducerDataPipeImpl::DestroyBuffer() {
 #ifndef NDEBUG
   // Scribble on the buffer to help detect use-after-frees. (This also helps the
   // unit test detect certain bugs without needing ASAN or similar.)
   if (buffer_)
     memset(buffer_.get(), 0xcd, capacity_num_bytes());
 #endif
   buffer_.reset();
 }

 size_t RemoteProducerDataPipeImpl::GetMaxNumBytesToWrite() {
   size_t next_index = start_index_ + current_num_bytes_;
   if (next_index >= capacity_num_bytes()) {
     next_index %= capacity_num_bytes();
     DCHECK_GE(start_index_, next_index);
     DCHECK_EQ(start_index_ - next_index,
               capacity_num_bytes() - current_num_bytes_);
     return start_index_ - next_index;
   }
   return capacity_num_bytes() - next_index;
 }

 size_t RemoteProducerDataPipeImpl::GetMaxNumBytesToRead() {
   if (start_index_ + current_num_bytes_ > capacity_num_bytes())
     return capacity_num_bytes() - start_index_;
   return current_num_bytes_;
 }

 void RemoteProducerDataPipeImpl::MarkDataAsConsumed(size_t num_bytes) {
   DCHECK_LE(num_bytes, current_num_bytes_);
   start_index_ += num_bytes;
   start_index_ %= capacity_num_bytes();
   current_num_bytes_ -= num_bytes;

   if (!producer_open()) {
     DCHECK(!channel_endpoint_);
     return;
   }

   RemoteDataPipeAck ack_data = {};
   ack_data.num_bytes_consumed = static_cast<uint32_t>(num_bytes);
   scoped_ptr<MessageInTransit> message(new MessageInTransit(
       MessageInTransit::Type::ENDPOINT_CLIENT,
       MessageInTransit::Subtype::ENDPOINT_CLIENT_DATA_PIPE_ACK,
       static_cast<uint32_t>(sizeof(ack_data)), &ack_data));
   if (!channel_endpoint_->EnqueueMessage(message.Pass()))
     Disconnect();
 }

 void RemoteProducerDataPipeImpl::Disconnect() {
   DCHECK(producer_open());
   DCHECK(channel_endpoint_);
   owner()->SetProducerClosedNoLock();
   channel_endpoint_->DetachFromClient();
   channel_endpoint_ = nullptr;
   // If the consumer is still open and we still have data, we have to keep the
   // buffer around. Currently, we won't free it even if it empties later. (We
   // could do this -- requiring a check on every read -- but that seems to be
   // optimizing for the uncommon case.)
   if (!consumer_open() || !current_num_bytes_)
     DestroyBuffer();
 }

 }  // namespace system
 }  // namespace mojo
	// Copyright 2015 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 "mojo/edk/system/remote_producer_data_pipe_impl.h"

	#include <string.h>

	#include <algorithm>

	#include "base/logging.h"
	#include "base/memory/scoped_ptr.h"
	#include "mojo/edk/system/channel.h"
	#include "mojo/edk/system/channel_endpoint.h"
	#include "mojo/edk/system/configuration.h"
	#include "mojo/edk/system/data_pipe.h"
	#include "mojo/edk/system/message_in_transit.h"
	#include "mojo/edk/system/message_in_transit_queue.h"
	#include "mojo/edk/system/remote_consumer_data_pipe_impl.h"
	#include "mojo/edk/system/remote_data_pipe_ack.h"

	namespace mojo {
	namespace system {

	namespace {

	bool ValidateIncomingMessage(size_t element_num_bytes,
	size_t capacity_num_bytes,
	size_t current_num_bytes,
	const MessageInTransit* message) {
	// We should only receive endpoint client messages.
	DCHECK_EQ(message->type(), MessageInTransit::Type::ENDPOINT_CLIENT);

	// But we should check the subtype; only take data messages.
	if (message->subtype() != MessageInTransit::Subtype::ENDPOINT_CLIENT_DATA) {
	LOG(WARNING) << "Received message of unexpected subtype: "
	<< message->subtype();
	return false;
	}

	const size_t num_bytes = message->num_bytes();
	const size_t max_num_bytes = capacity_num_bytes - current_num_bytes;
	if (num_bytes > max_num_bytes) {
	LOG(WARNING) << "Received too much data: " << num_bytes
	<< " bytes (maximum: " << max_num_bytes << " bytes)";
	return false;
	}

	if (num_bytes % element_num_bytes != 0) {
	LOG(WARNING) << "Received data not a multiple of element size: "
	<< num_bytes << " bytes (element size: " << element_num_bytes
	<< " bytes)";
	return false;
	}

	return true;
	}

	} // namespace

	RemoteProducerDataPipeImpl::RemoteProducerDataPipeImpl(
	ChannelEndpoint* channel_endpoint)
	: channel_endpoint_(channel_endpoint),
	start_index_(0),
	current_num_bytes_(0) {
	// Note: \|buffer_\| is lazily allocated.
	}

	RemoteProducerDataPipeImpl::RemoteProducerDataPipeImpl(
	ChannelEndpoint* channel_endpoint,
	scoped_ptr<char, base::AlignedFreeDeleter> buffer,
	size_t start_index,
	size_t current_num_bytes)
	: channel_endpoint_(channel_endpoint),
	buffer_(buffer.Pass()),
	start_index_(start_index),
	current_num_bytes_(current_num_bytes) {
	DCHECK(buffer_ \|\| !current_num_bytes);
	}

	// static
	bool RemoteProducerDataPipeImpl::ProcessMessagesFromIncomingEndpoint(
	const MojoCreateDataPipeOptions& validated_options,
	MessageInTransitQueue* messages,
	scoped_ptr<char, base::AlignedFreeDeleter>* buffer,
	size_t* buffer_num_bytes) {
	DCHECK(!*buffer); // Not wrong, but unlikely.

	const size_t element_num_bytes = validated_options.element_num_bytes;
	const size_t capacity_num_bytes = validated_options.capacity_num_bytes;

	scoped_ptr<char, base::AlignedFreeDeleter> new_buffer(static_cast<char*>(
	base::AlignedAlloc(capacity_num_bytes,
	GetConfiguration().data_pipe_buffer_alignment_bytes)));

	size_t current_num_bytes = 0;
	if (messages) {
	while (!messages->IsEmpty()) {
	scoped_ptr<MessageInTransit> message(messages->GetMessage());
	if (!ValidateIncomingMessage(element_num_bytes, capacity_num_bytes,
	current_num_bytes, message.get())) {
	messages->Clear();
	return false;
	}

	memcpy(new_buffer.get() + current_num_bytes, message->bytes(),
	message->num_bytes());
	current_num_bytes += message->num_bytes();
	}
	}

	*buffer = new_buffer.Pass();
	*buffer_num_bytes = current_num_bytes;
	return true;
	}

	RemoteProducerDataPipeImpl::~RemoteProducerDataPipeImpl() {
	}

	void RemoteProducerDataPipeImpl::ProducerClose() {
	NOTREACHED();
	}

	MojoResult RemoteProducerDataPipeImpl::ProducerWriteData(
	UserPointer<const void> /elements/,
	UserPointer<uint32_t> /num_bytes/,
	uint32_t /max_num_bytes_to_write/,
	uint32_t /min_num_bytes_to_write/) {
	NOTREACHED();
	return MOJO_RESULT_INTERNAL;
	}

	MojoResult RemoteProducerDataPipeImpl::ProducerBeginWriteData(
	UserPointer<void> /buffer*/,
	UserPointer<uint32_t> /buffer_num_bytes/,
	uint32_t /min_num_bytes_to_write/) {
	NOTREACHED();
	return MOJO_RESULT_INTERNAL;
	}

	MojoResult RemoteProducerDataPipeImpl::ProducerEndWriteData(
	uint32_t /num_bytes_written/) {
	NOTREACHED();
	return MOJO_RESULT_INTERNAL;
	}

	HandleSignalsState RemoteProducerDataPipeImpl::ProducerGetHandleSignalsState()
	const {
	return HandleSignalsState();
	}

	void RemoteProducerDataPipeImpl::ProducerStartSerialize(
	Channel* /channel/,
	size_t* /max_size/,
	size_t* /max_platform_handles/) {
	NOTREACHED();
	}

	bool RemoteProducerDataPipeImpl::ProducerEndSerialize(
	Channel* /channel/,
	void* /destination/,
	size_t* /actual_size/,
	embedder::PlatformHandleVector* /platform_handles/) {
	NOTREACHED();
	return false;
	}

	void RemoteProducerDataPipeImpl::ConsumerClose() {
	if (producer_open())
	Disconnect();
	current_num_bytes_ = 0;
	}

	MojoResult RemoteProducerDataPipeImpl::ConsumerReadData(
	UserPointer<void> elements,
	UserPointer<uint32_t> num_bytes,
	uint32_t max_num_bytes_to_read,
	uint32_t min_num_bytes_to_read,
	bool peek) {
	DCHECK_EQ(max_num_bytes_to_read % element_num_bytes(), 0u);
	DCHECK_EQ(min_num_bytes_to_read % element_num_bytes(), 0u);
	DCHECK_GT(max_num_bytes_to_read, 0u);

	if (min_num_bytes_to_read > current_num_bytes_) {
	// Don't return "should wait" since you can't wait for a specified amount of
	// data.
	return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	size_t num_bytes_to_read =
	std::min(static_cast<size_t>(max_num_bytes_to_read), current_num_bytes_);
	if (num_bytes_to_read == 0) {
	return producer_open() ? MOJO_RESULT_SHOULD_WAIT
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	// The amount we can read in our first \|memcpy()\|.
	size_t num_bytes_to_read_first =
	std::min(num_bytes_to_read, GetMaxNumBytesToRead());
	elements.PutArray(buffer_.get() + start_index_, num_bytes_to_read_first);

	if (num_bytes_to_read_first < num_bytes_to_read) {
	// The "second read index" is zero.
	elements.At(num_bytes_to_read_first)
	.PutArray(buffer_.get(), num_bytes_to_read - num_bytes_to_read_first);
	}

	if (!peek)
	MarkDataAsConsumed(num_bytes_to_read);
	num_bytes.Put(static_cast<uint32_t>(num_bytes_to_read));
	return MOJO_RESULT_OK;
	}

	MojoResult RemoteProducerDataPipeImpl::ConsumerDiscardData(
	UserPointer<uint32_t> num_bytes,
	uint32_t max_num_bytes_to_discard,
	uint32_t min_num_bytes_to_discard) {
	DCHECK_EQ(max_num_bytes_to_discard % element_num_bytes(), 0u);
	DCHECK_EQ(min_num_bytes_to_discard % element_num_bytes(), 0u);
	DCHECK_GT(max_num_bytes_to_discard, 0u);

	if (min_num_bytes_to_discard > current_num_bytes_) {
	// Don't return "should wait" since you can't wait for a specified amount of
	// data.
	return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	// Be consistent with other operations; error if no data available.
	if (current_num_bytes_ == 0) {
	return producer_open() ? MOJO_RESULT_SHOULD_WAIT
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	size_t num_bytes_to_discard = std::min(
	static_cast<size_t>(max_num_bytes_to_discard), current_num_bytes_);
	MarkDataAsConsumed(num_bytes_to_discard);
	num_bytes.Put(static_cast<uint32_t>(num_bytes_to_discard));
	return MOJO_RESULT_OK;
	}

	MojoResult RemoteProducerDataPipeImpl::ConsumerQueryData(
	UserPointer<uint32_t> num_bytes) {
	// Note: This cast is safe, since the capacity fits into a \|uint32_t\|.
	num_bytes.Put(static_cast<uint32_t>(current_num_bytes_));
	return MOJO_RESULT_OK;
	}

	MojoResult RemoteProducerDataPipeImpl::ConsumerBeginReadData(
	UserPointer<const void*> buffer,
	UserPointer<uint32_t> buffer_num_bytes,
	uint32_t min_num_bytes_to_read) {
	size_t max_num_bytes_to_read = GetMaxNumBytesToRead();
	if (min_num_bytes_to_read > max_num_bytes_to_read) {
	// Don't return "should wait" since you can't wait for a specified amount of
	// data.
	return producer_open() ? MOJO_RESULT_OUT_OF_RANGE
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	// Don't go into a two-phase read if there's no data.
	if (max_num_bytes_to_read == 0) {
	return producer_open() ? MOJO_RESULT_SHOULD_WAIT
	: MOJO_RESULT_FAILED_PRECONDITION;
	}

	buffer.Put(buffer_.get() + start_index_);
	buffer_num_bytes.Put(static_cast<uint32_t>(max_num_bytes_to_read));
	set_consumer_two_phase_max_num_bytes_read(
	static_cast<uint32_t>(max_num_bytes_to_read));
	return MOJO_RESULT_OK;
	}

	MojoResult RemoteProducerDataPipeImpl::ConsumerEndReadData(
	uint32_t num_bytes_read) {
	DCHECK_LE(num_bytes_read, consumer_two_phase_max_num_bytes_read());
	DCHECK_EQ(num_bytes_read % element_num_bytes(), 0u);
	DCHECK_LE(start_index_ + num_bytes_read, capacity_num_bytes());
	MarkDataAsConsumed(num_bytes_read);
	set_consumer_two_phase_max_num_bytes_read(0);
	return MOJO_RESULT_OK;
	}

	HandleSignalsState RemoteProducerDataPipeImpl::ConsumerGetHandleSignalsState()
	const {
	HandleSignalsState rv;
	if (current_num_bytes_ > 0) {
	if (!consumer_in_two_phase_read())
	rv.satisfied_signals \|= MOJO_HANDLE_SIGNAL_READABLE;
	rv.satisfiable_signals \|= MOJO_HANDLE_SIGNAL_READABLE;
	} else if (producer_open()) {
	rv.satisfiable_signals \|= MOJO_HANDLE_SIGNAL_READABLE;
	}
	if (!producer_open())
	rv.satisfied_signals \|= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
	rv.satisfiable_signals \|= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
	return rv;
	}

	void RemoteProducerDataPipeImpl::ConsumerStartSerialize(
	Channel* channel,
	size_t* max_size,
	size_t* max_platform_handles) {
	*max_size = sizeof(SerializedDataPipeConsumerDispatcher) +
	channel->GetSerializedEndpointSize();
	*max_platform_handles = 0;
	}

	bool RemoteProducerDataPipeImpl::ConsumerEndSerialize(
	Channel* channel,
	void* destination,
	size_t* actual_size,
	embedder::PlatformHandleVector* platform_handles) {
	SerializedDataPipeConsumerDispatcher* s =
	static_cast<SerializedDataPipeConsumerDispatcher*>(destination);
	s->validated_options = validated_options();
	void* destination_for_endpoint = static_cast<char*>(destination) +
	sizeof(SerializedDataPipeConsumerDispatcher);

	MessageInTransitQueue message_queue;
	ConvertDataToMessages(buffer_.get(), &start_index_, &current_num_bytes_,
	&message_queue);

	if (!producer_open()) {
	// Case 1: The producer is closed.
	channel->SerializeEndpointWithClosedPeer(destination_for_endpoint,
	&message_queue);
	*actual_size = sizeof(SerializedDataPipeConsumerDispatcher) +
	channel->GetSerializedEndpointSize();
	return true;
	}

	// Case 2: The producer isn't closed. We pass \|channel_endpoint\| back to the
	// \|Channel\|. There's no reason for us to continue to exist afterwards.

	// Note: We don't use \|port\|.
	scoped_refptr<ChannelEndpoint> channel_endpoint;
	channel_endpoint.swap(channel_endpoint_);
	channel->SerializeEndpointWithRemotePeer(destination_for_endpoint,
	&message_queue, channel_endpoint);
	owner()->SetProducerClosedNoLock();

	*actual_size = sizeof(SerializedDataPipeConsumerDispatcher) +
	channel->GetSerializedEndpointSize();
	return true;
	}

	bool RemoteProducerDataPipeImpl::OnReadMessage(unsigned /port/,
	MessageInTransit* message) {
	if (!producer_open()) {
	// This will happen only on the rare occasion that the call to
	// \|OnReadMessage()\| is racing with us calling
	// \|ChannelEndpoint::ReplaceClient()\|, in which case we reject the message,
	// and the \|ChannelEndpoint\| can retry (calling the new client's
	// \|OnReadMessage()\|).
	DCHECK(!channel_endpoint_);
	return false;
	}

	// Otherwise, we take ownership of the message. (This means that we should
	// always return true below.)
	scoped_ptr<MessageInTransit> msg(message);

	if (!ValidateIncomingMessage(element_num_bytes(), capacity_num_bytes(),
	current_num_bytes_, msg.get())) {
	Disconnect();
	return true;
	}

	size_t num_bytes = msg->num_bytes();
	// The amount we can write in our first copy.
	size_t num_bytes_to_copy_first = std::min(num_bytes, GetMaxNumBytesToWrite());
	// Do the first (and possibly only) copy.
	size_t first_write_index =
	(start_index_ + current_num_bytes_) % capacity_num_bytes();
	EnsureBuffer();
	memcpy(buffer_.get() + first_write_index, msg->bytes(),
	num_bytes_to_copy_first);

	if (num_bytes_to_copy_first < num_bytes) {
	// The "second write index" is zero.
	memcpy(buffer_.get(),
	static_cast<const char*>(msg->bytes()) + num_bytes_to_copy_first,
	num_bytes - num_bytes_to_copy_first);
	}

	current_num_bytes_ += num_bytes;
	DCHECK_LE(current_num_bytes_, capacity_num_bytes());
	return true;
	}

	void RemoteProducerDataPipeImpl::OnDetachFromChannel(unsigned /port/) {
	if (!producer_open()) {
	DCHECK(!channel_endpoint_);
	return;
	}

	Disconnect();
	}

	void RemoteProducerDataPipeImpl::EnsureBuffer() {
	DCHECK(producer_open());
	if (buffer_)
	return;
	buffer_.reset(static_cast<char*>(
	base::AlignedAlloc(capacity_num_bytes(),
	GetConfiguration().data_pipe_buffer_alignment_bytes)));
	}

	void RemoteProducerDataPipeImpl::DestroyBuffer() {
	#ifndef NDEBUG
	// Scribble on the buffer to help detect use-after-frees. (This also helps the
	// unit test detect certain bugs without needing ASAN or similar.)
	if (buffer_)
	memset(buffer_.get(), 0xcd, capacity_num_bytes());
	#endif
	buffer_.reset();
	}

	size_t RemoteProducerDataPipeImpl::GetMaxNumBytesToWrite() {
	size_t next_index = start_index_ + current_num_bytes_;
	if (next_index >= capacity_num_bytes()) {
	next_index %= capacity_num_bytes();
	DCHECK_GE(start_index_, next_index);
	DCHECK_EQ(start_index_ - next_index,
	capacity_num_bytes() - current_num_bytes_);
	return start_index_ - next_index;
	}
	return capacity_num_bytes() - next_index;
	}

	size_t RemoteProducerDataPipeImpl::GetMaxNumBytesToRead() {
	if (start_index_ + current_num_bytes_ > capacity_num_bytes())
	return capacity_num_bytes() - start_index_;
	return current_num_bytes_;
	}

	void RemoteProducerDataPipeImpl::MarkDataAsConsumed(size_t num_bytes) {
	DCHECK_LE(num_bytes, current_num_bytes_);
	start_index_ += num_bytes;
	start_index_ %= capacity_num_bytes();
	current_num_bytes_ -= num_bytes;

	if (!producer_open()) {
	DCHECK(!channel_endpoint_);
	return;
	}

	RemoteDataPipeAck ack_data = {};
	ack_data.num_bytes_consumed = static_cast<uint32_t>(num_bytes);
	scoped_ptr<MessageInTransit> message(new MessageInTransit(
	MessageInTransit::Type::ENDPOINT_CLIENT,
	MessageInTransit::Subtype::ENDPOINT_CLIENT_DATA_PIPE_ACK,
	static_cast<uint32_t>(sizeof(ack_data)), &ack_data));
	if (!channel_endpoint_->EnqueueMessage(message.Pass()))
	Disconnect();
	}

	void RemoteProducerDataPipeImpl::Disconnect() {
	DCHECK(producer_open());
	DCHECK(channel_endpoint_);
	owner()->SetProducerClosedNoLock();
	channel_endpoint_->DetachFromClient();
	channel_endpoint_ = nullptr;
	// If the consumer is still open and we still have data, we have to keep the
	// buffer around. Currently, we won't free it even if it empties later. (We
	// could do this -- requiring a check on every read -- but that seems to be
	// optimizing for the uncommon case.)
	if (!consumer_open() \|\| !current_num_bytes_)
	DestroyBuffer();
	}

	} // namespace system
	} // namespace mojo