[mojo] Ports EDK

mojo/edk/system/ports/message_queue.h

+// 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 <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 = 0xFFFFFFFF;
+
+// 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. The selector may be null.
+  void GetNextMessageIf(std::function<bool(const Message&)> selector,
+                        ScopedMessage* message);
+
+  // 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_