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// Copyright 2016 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.
#ifndef MOJO_CORE_PORTS_MESSAGE_QUEUE_H_
#define MOJO_CORE_PORTS_MESSAGE_QUEUE_H_
#include <stdint.h>
#include <limits>
#include <memory>
#include <vector>
#include "mojo/core/ports/event.h"
namespace mojo {
namespace core {
namespace ports {
constexpr uint64_t kInitialSequenceNum = 1;
constexpr uint64_t kInvalidSequenceNum = std::numeric_limits<uint64_t>::max();
class MessageFilter;
// An incoming message queue for a port. MessageQueue keeps track of the highest
// known sequence number and can indicate whether the next sequential message is
// available. Thus the queue enforces message ordering for the consumer without
// enforcing it for the producer (see AcceptMessage() below.)
class MessageQueue {
public:
explicit MessageQueue();
explicit MessageQueue(uint64_t next_sequence_num);
~MessageQueue();
MessageQueue(const MessageQueue&) = delete;
void operator=(const MessageQueue&) = delete;
void set_signalable(bool value) { signalable_ = value; }
uint64_t next_sequence_num() const { return next_sequence_num_; }
bool HasNextMessage() const;
// Gives ownership of the message. If |filter| is non-null, the next message
// will only be retrieved if the filter successfully matches it.
void GetNextMessage(mozilla::UniquePtr<UserMessageEvent>* message,
MessageFilter* filter);
// Takes ownership of the message. Note: Messages are ordered, so while we
// have added a message to the queue, we may still be waiting on a message
// ahead of this one before we can let any of the messages be returned by
// GetNextMessage.
//
// Furthermore, once has_next_message is set to true, it will remain false
// until GetNextMessage is called enough times to return a null message.
// In other words, has_next_message acts like an edge trigger.
//
void AcceptMessage(mozilla::UniquePtr<UserMessageEvent> message,
bool* has_next_message);
// Takes all messages from this queue. Used to safely destroy queued messages
// without holding any Port lock.
void TakeAllMessages(
std::vector<mozilla::UniquePtr<UserMessageEvent>>* messages);
// The number of messages queued here, regardless of whether the next expected
// message has arrived yet.
size_t queued_message_count() const { return heap_.size(); }
// The aggregate memory size in bytes of all messages queued here, regardless
// of whether the next expected message has arrived yet.
size_t queued_num_bytes() const { return total_queued_bytes_; }
private:
std::vector<mozilla::UniquePtr<UserMessageEvent>> heap_;
uint64_t next_sequence_num_;
bool signalable_ = true;
size_t total_queued_bytes_ = 0;
};
} // namespace ports
} // namespace core
} // namespace mojo
#endif // MOJO_CORE_PORTS_MESSAGE_QUEUE_H_
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