/*
 * JBoss, Home of Professional Open Source
 * Copyright 2011, Red Hat, Inc. and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.mobicents.protocols.ss7.m3ua.impl.parameter;

import java.nio.ByteBuffer;

import org.mobicents.protocols.ss7.m3ua.parameter.Parameter;

/**
 * @author amit bhayani
 * @author kulikov
 */
public abstract class ParameterImpl implements Parameter {

    protected volatile short tag;
    protected volatile short length;

    public short getTag() {
        return tag;
    }

    protected abstract byte[] getValue();

    // public void encode(OutputStream out) throws IOException {
    // // obtain encoded value
    // byte[] value = getValue();
    //
    // // encode tag
    // out.write((byte) (tag >> 8));
    // out.write((byte) (tag));
    //
    // // encode length including value, tag and length field itself
    // length = (short) (value.length + 4);
    //
    // out.write((byte) (length >> 8));
    // out.write((byte) (length));
    //
    // // encode value
    // out.write(value);
    // }

    public void write(ByteBuffer buffer) {
        // obtain encoded value
        byte[] value = getValue();

        // encode tag
        buffer.put((byte) (tag >> 8));
        buffer.put((byte) (tag));

        // encode length including value, tag and length field itself
        length = (short) (value.length + 4);

        buffer.put((byte) (length >> 8));
        buffer.put((byte) (length));

        // encode value
        buffer.put(value);

        /*
         * The total length of a parameter (including Tag, Parameter Length, and Value fields) MUST be a multiple of 4 octets.
         * If the length of the parameter is not a multiple of 4 octets, the sender pads the Parameter at the end (i.e., after
         * the Parameter Value field) with all zero octets. The length of the padding is NOT included in the parameter length
         * field. A sender MUST NOT pad with more than 3 octets. The receiver MUST ignore the padding octets.
         */
        int remainder = (4 - length % 4);
        if (remainder < 4) {
            while (remainder > 0) {
                buffer.put((byte) 0x00);
                remainder--;
            }
        }
    }

}