[mojo] Ports EDK

mojo/edk/system/ports/message.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_H_
+#define MOJO_EDK_SYSTEM_PORTS_MESSAGE_H_
+
+#include <stddef.h>
+
+#include "base/memory/scoped_ptr.h"
+#include "mojo/edk/system/ports/name.h"
+
+namespace mojo {
+namespace edk {
+namespace ports {
+
+// A message consists of a header (array of bytes), payload (array of bytes)
+// and an array of ports. The header is used by the Node implementation.
+//
+// This class is designed to be subclassed, and the subclass is responsible for
+// providing the underlying storage. The header size will be aligned, and it
+// should be followed in memory by the array of ports and finally the payload.
+//
+// NOTE: This class does not manage the lifetime of the ports it references.
+class Message {
+ public:
+  virtual ~Message() {}
+
+  // Inspect the message at |bytes| and return the size of each section.
+  static void Parse(const void* bytes,
+                    size_t num_bytes,
+                    size_t* num_header_bytes,
+                    size_t* num_payload_bytes,
+                    size_t* num_ports_bytes);
+
+  void* mutable_header_bytes() { return start_; }
+  const void* header_bytes() const { return start_; }
+  size_t num_header_bytes() const { return num_header_bytes_; }
+
+  void* mutable_payload_bytes() {
+    return start_ + num_header_bytes_ + num_ports_bytes_;
+  }
+  const void* payload_bytes() const {
+    return const_cast<Message*>(this)->mutable_payload_bytes();
+  }
+  size_t num_payload_bytes() const { return num_payload_bytes_; }
+
+  PortName* mutable_ports() {
+    return reinterpret_cast<PortName*>(start_ + num_header_bytes_);
+  }
+  const PortName* ports() const {
+    return const_cast<Message*>(this)->mutable_ports();
+  }
+  size_t num_ports_bytes() const { return num_ports_bytes_; }
+  size_t num_ports() const { return num_ports_bytes_ / sizeof(PortName); }
+
+ protected:
+  // Constructs a new Message base for a user message.
+  //
+  // Note: You MUST call InitializeUserMessageHeader() before this Message is
+  // ready for transmission.
+  Message(size_t num_payload_bytes, size_t num_ports);
+
+  // Constructs a new Message base for an internal message. Do NOT call
+  // InitializeUserMessageHeader() when using this constructor.
+  Message(size_t num_header_bytes,
+          size_t num_payload_bytes,
+          size_t num_ports_bytes);
+
+  Message(const Message& other) = delete;
+  void operator=(const Message& other) = delete;
+
+  // Initializes the header in a newly allocated message buffer to carry a
+  // user message.
+  void InitializeUserMessageHeader(void* start);
+
+  // Note: storage is [header][ports][payload].
+  char* start_ = nullptr;
+  size_t num_ports_ = 0;
+  size_t num_header_bytes_ = 0;
+  size_t num_ports_bytes_ = 0;
+  size_t num_payload_bytes_ = 0;
+};
+
+using ScopedMessage = scoped_ptr<Message>;
+
+}  // namespace ports
+}  // namespace edk
+}  // namespace mojo
+
+#endif  // MOJO_EDK_SYSTEM_PORTS_MESSAGE_H_