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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_H_
#define MOJO_EDK_SYSTEM_PORTS_MESSAGE_H_
#include <stddef.h>
#include <memory>
#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. Returns
// |false| if the message is malformed and |true| otherwise.
static bool 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 = std::unique_ptr<Message>;
} // namespace ports
} // namespace edk
} // namespace mojo
#endif // MOJO_EDK_SYSTEM_PORTS_MESSAGE_H_
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