/*
 * $Id$
 *
 * 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._3c90x;

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 epr
 */
public class _3c90xTxBuffer implements _3c90xConstants {

    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;
    /**
     * Offset within mem of first ethernet frame
     */
    private final int firstFrameOffset;
    /**
     * 32-bit address first DPD
     */
    private final Address firstDPDAddress;
    /**
     * 32-bit address of first ethernet frame
     */
    private final Address firstFrameAddress;

    /**
     * Create a new instance
     * 
     * @param rm
     */
    public _3c90xTxBuffer(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 = memAddr.toInt();
        int offset = 0;
        // Align on 16-byte boundary
        while ((addr & 15) != 0) {
            addr++;
            offset++;
        }

        this.firstDPDOffset = offset;
        this.firstDPDAddress = memAddr.add(firstDPDOffset);
        this.firstFrameOffset = firstDPDOffset + DPD_SIZE;
        this.firstFrameAddress = memAddr.add(firstFrameOffset);
    }

    /**
     * Initialize this ring to its default (empty) state
     */
    public void initialize(SocketBuffer src) throws IllegalArgumentException {
        // Setup the DPD
        final int dpdOffset = firstDPDOffset;

        // 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, firstFrameOffset, 0, len);
        // Set next DPD ptr
        mem.setInt(dpdOffset + 0, 0);
        // Set frame start header
        mem.setInt(dpdOffset + 4, 0x8000); // txIndicate
        // Set fragment address
        mem.setInt(dpdOffset + 8, firstFrameAddress.toInt());
        // Set fragment size
        mem.setInt(dpdOffset + 12, len | (1 << 31));
    }

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