/*
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * This library 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 library 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 library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.driver.net.rtl8139;

import org.jnode.net.SocketBuffer;
import org.jnode.net.ethernet.EthernetConstants;
import org.jnode.system.resource.MemoryResource;
import org.jnode.system.resource.ResourceManager;
import org.vmmagic.unboxed.Address;

/**
 * @author Martin Husted Hartvig
 */

public class RTL8139TxBuffer implements RTL8139Constants {

    private static final int DPD_SIZE = 16;

    private static final int FRAME_SIZE = EthernetConstants.ETH_FRAME_LEN;

    /**
     * The actual data
     */
    private final byte[] data;

    /**
     * MemoryResource mapper around data
     */
    private final MemoryResource mem;

    /**
     * Offset within mem of first DPD
     */
    private final int firstDPDOffset;

    /**
     * 32-bit address first DPD
     */
    private final Address firstDPDAddress;

    /**
     * Create a new instance
     *
     * @param rm
     */

    public RTL8139TxBuffer(ResourceManager rm) {
        // Create a large enough buffer
        final int size = (DPD_SIZE + FRAME_SIZE) + 16 /* alignment */;
        this.data = new byte[size];
        this.mem = rm.asMemoryResource(data);

        final Address memAddr = mem.getAddress();
        // int addr = Address.as32bit(memAddr);
        int offset = 0;

        this.firstDPDOffset = offset;
        this.firstDPDAddress = memAddr.add(firstDPDOffset);
    }

    /**
     * Initialize this ring to its default (empty) state
     */
    public void initialize(SocketBuffer src) throws IllegalArgumentException {
        // Setup the DPD

        // Copy the data from the buffer
        final int len = src.getSize();
        if (len > FRAME_SIZE) {
            throw new IllegalArgumentException("Length must be <= ETH_FRAME_LEN");
        }

        src.get(data, firstDPDOffset, 0, len);
    }

    /**
     * Gets the address of the first DPD in this buffer.
     */
    public Address getFirstDPDAddress() {
        return firstDPDAddress;
    }
}