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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_EDK_SYSTEM_PORTS_MESSAGE_QUEUE_H_
#define MOJO_EDK_SYSTEM_PORTS_MESSAGE_QUEUE_H_
#include <stdint.h>
#include <deque>
#include <functional>
#include <limits>
#include <vector>
#include "base/macros.h"
#include "mojo/edk/system/ports/message.h"
namespace mojo {
namespace edk {
namespace ports {
const uint64_t kInitialSequenceNum = 1;
const 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();
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(ScopedMessage* 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(ScopedMessage message, bool* has_next_message);
// Returns all of the ports referenced by messages in this message queue.
void GetReferencedPorts(std::deque<PortName>* ports);
private:
std::vector<ScopedMessage> heap_;
uint64_t next_sequence_num_;
bool signalable_ = true;
DISALLOW_COPY_AND_ASSIGN(MessageQueue);
};
} // namespace ports
} // namespace edk
} // namespace mojo
#endif // MOJO_EDK_SYSTEM_PORTS_MESSAGE_QUEUE_H_
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