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Efficient reliable UDP unicast, UDP multicast, and IPC transport protocol.
There is a newer version: 1.46.7
/*
 * Copyright 2014-2017 Real Logic Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.aeron;

import org.agrona.DirectBuffer;
import org.agrona.concurrent.UnsafeBuffer;

import java.nio.ByteBuffer;

import static org.agrona.BitUtil.*;

/**
 * Description of the command and control file used between driver and clients
 *
 * File Layout
 *  *  +----------------------------+
 *  |      Aeron CnC Version     |
 *  +----------------------------+
 *  |          Meta Data         |
 *  +----------------------------+
 *  |      to-driver Buffer      |
 *  +----------------------------+
 *  |      to-clients Buffer     |
 *  +----------------------------+
 *  |   Counter Metadata Buffer  |
 *  +----------------------------+
 *  |    Counter Values Buffer   |
 *  +----------------------------+
 *  |          Error Log         |
 *  +----------------------------+
 * 
 *
 * Meta Data Layout (CnC Version 6)
 *  *  +----------------------------+
 *  |   to-driver buffer length  |
 *  +----------------------------+
 *  |  to-clients buffer length  |
 *  +----------------------------+
 *  |   metadata buffer length   |
 *  +----------------------------+
 *  |    values buffer length    |
 *  +----------------------------+
 *  |   Client Liveness Timeout  |
 *  |                            |
 *  +----------------------------+
 *  |      Error Log length      |
 *  +----------------------------+
 * 
 */
public class CncFileDescriptor
{
    public static final String CNC_FILE = "cnc.dat";

    public static final int CNC_VERSION = 6;

    public static final int CNC_VERSION_FIELD_OFFSET;
    public static final int CNC_METADATA_OFFSET;

    /* Meta Data Offsets (offsets within the meta data section) */

    public static final int TO_DRIVER_BUFFER_LENGTH_FIELD_OFFSET;
    public static final int TO_CLIENTS_BUFFER_LENGTH_FIELD_OFFSET;
    public static final int COUNTERS_METADATA_BUFFER_LENGTH_FIELD_OFFSET;
    public static final int COUNTERS_VALUES_BUFFER_LENGTH_FIELD_OFFSET;
    public static final int CLIENT_LIVENESS_TIMEOUT_FIELD_OFFSET;
    public static final int ERROR_LOG_BUFFER_LENGTH_FIELD_OFFSET;

    static
    {
        CNC_VERSION_FIELD_OFFSET = 0;
        CNC_METADATA_OFFSET = CNC_VERSION_FIELD_OFFSET + SIZE_OF_INT;

        TO_DRIVER_BUFFER_LENGTH_FIELD_OFFSET = 0;
        TO_CLIENTS_BUFFER_LENGTH_FIELD_OFFSET = TO_DRIVER_BUFFER_LENGTH_FIELD_OFFSET + SIZE_OF_INT;
        COUNTERS_METADATA_BUFFER_LENGTH_FIELD_OFFSET = TO_CLIENTS_BUFFER_LENGTH_FIELD_OFFSET + SIZE_OF_INT;
        COUNTERS_VALUES_BUFFER_LENGTH_FIELD_OFFSET = COUNTERS_METADATA_BUFFER_LENGTH_FIELD_OFFSET + SIZE_OF_INT;
        CLIENT_LIVENESS_TIMEOUT_FIELD_OFFSET = COUNTERS_VALUES_BUFFER_LENGTH_FIELD_OFFSET + SIZE_OF_INT;
        ERROR_LOG_BUFFER_LENGTH_FIELD_OFFSET = CLIENT_LIVENESS_TIMEOUT_FIELD_OFFSET + SIZE_OF_LONG;
    }

    public static final int META_DATA_LENGTH = ERROR_LOG_BUFFER_LENGTH_FIELD_OFFSET + SIZE_OF_INT;

    public static final int END_OF_METADATA_OFFSET = align(SIZE_OF_INT + META_DATA_LENGTH, (CACHE_LINE_LENGTH * 2));

    /**
     * Compute the length of the cnc file and return it.
     *
     * @param totalLengthOfBuffers in bytes
     * @return cnc file length in bytes
     */
    public static int computeCncFileLength(final int totalLengthOfBuffers)
    {
        return END_OF_METADATA_OFFSET + totalLengthOfBuffers;
    }

    public static int cncVersionOffset(final int baseOffset)
    {
        return baseOffset + CNC_VERSION_FIELD_OFFSET;
    }

    public static int toDriverBufferLengthOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + TO_DRIVER_BUFFER_LENGTH_FIELD_OFFSET;
    }

    public static int toClientsBufferLengthOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + TO_CLIENTS_BUFFER_LENGTH_FIELD_OFFSET;
    }

    public static int countersMetaDataBufferLengthOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + COUNTERS_METADATA_BUFFER_LENGTH_FIELD_OFFSET;
    }

    public static int countersValuesBufferLengthOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + COUNTERS_VALUES_BUFFER_LENGTH_FIELD_OFFSET;
    }

    public static int clientLivenessTimeoutOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + CLIENT_LIVENESS_TIMEOUT_FIELD_OFFSET;
    }

    public static int errorLogBufferLengthOffset(final int baseOffset)
    {
        return baseOffset + CNC_METADATA_OFFSET + ERROR_LOG_BUFFER_LENGTH_FIELD_OFFSET;
    }

    public static void fillMetaData(
        final UnsafeBuffer cncMetaDataBuffer,
        final int toDriverBufferLength,
        final int toClientsBufferLength,
        final int counterMetaDataBufferLength,
        final int counterValuesBufferLength,
        final long clientLivenessTimeout,
        final int errorLogBufferLength)
    {
        cncMetaDataBuffer.putInt(toDriverBufferLengthOffset(0), toDriverBufferLength);
        cncMetaDataBuffer.putInt(toClientsBufferLengthOffset(0), toClientsBufferLength);
        cncMetaDataBuffer.putInt(countersMetaDataBufferLengthOffset(0), counterMetaDataBufferLength);
        cncMetaDataBuffer.putInt(countersValuesBufferLengthOffset(0), counterValuesBufferLength);
        cncMetaDataBuffer.putLong(clientLivenessTimeoutOffset(0), clientLivenessTimeout);
        cncMetaDataBuffer.putInt(errorLogBufferLengthOffset(0), errorLogBufferLength);
        cncMetaDataBuffer.putIntVolatile(cncVersionOffset(0), CNC_VERSION);
    }

    public static UnsafeBuffer createMetaDataBuffer(final ByteBuffer buffer)
    {
        return new UnsafeBuffer(buffer, 0, SIZE_OF_INT + META_DATA_LENGTH);
    }

    public static UnsafeBuffer createToDriverBuffer(final ByteBuffer buffer, final DirectBuffer metaDataBuffer)
    {
        return new UnsafeBuffer(buffer, END_OF_METADATA_OFFSET, metaDataBuffer.getInt(toDriverBufferLengthOffset(0)));
    }

    public static UnsafeBuffer createToClientsBuffer(final ByteBuffer buffer, final DirectBuffer metaDataBuffer)
    {
        final int offset = END_OF_METADATA_OFFSET + metaDataBuffer.getInt(toDriverBufferLengthOffset(0));

        return new UnsafeBuffer(buffer, offset, metaDataBuffer.getInt(toClientsBufferLengthOffset(0)));
    }

    public static UnsafeBuffer createCountersMetaDataBuffer(final ByteBuffer buffer, final DirectBuffer metaDataBuffer)
    {
        final int offset = END_OF_METADATA_OFFSET +
            metaDataBuffer.getInt(toDriverBufferLengthOffset(0)) +
            metaDataBuffer.getInt(toClientsBufferLengthOffset(0));

        return new UnsafeBuffer(buffer, offset, metaDataBuffer.getInt(countersMetaDataBufferLengthOffset(0)));
    }

    public static UnsafeBuffer createCountersValuesBuffer(final ByteBuffer buffer, final DirectBuffer metaDataBuffer)
    {
        final int offset = END_OF_METADATA_OFFSET +
            metaDataBuffer.getInt(toDriverBufferLengthOffset(0)) +
            metaDataBuffer.getInt(toClientsBufferLengthOffset(0)) +
            metaDataBuffer.getInt(countersMetaDataBufferLengthOffset(0));

        return new UnsafeBuffer(buffer, offset, metaDataBuffer.getInt(countersValuesBufferLengthOffset(0)));
    }

    public static UnsafeBuffer createErrorLogBuffer(final ByteBuffer buffer, final DirectBuffer metaDataBuffer)
    {
        final int offset = END_OF_METADATA_OFFSET +
            metaDataBuffer.getInt(toDriverBufferLengthOffset(0)) +
            metaDataBuffer.getInt(toClientsBufferLengthOffset(0)) +
            metaDataBuffer.getInt(countersMetaDataBufferLengthOffset(0)) +
            metaDataBuffer.getInt(countersValuesBufferLengthOffset(0));

        return new UnsafeBuffer(buffer, offset, metaDataBuffer.getInt(errorLogBufferLengthOffset(0)));
    }

    public static long clientLivenessTimeout(final DirectBuffer metaDataBuffer)
    {
        return metaDataBuffer.getLong(clientLivenessTimeoutOffset(0));
    }
}