LcnAddrGrp.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.lcn.common;

/**
 * Represents an LCN group address.
 * Can be used as a key in maps.
 * Hash codes are guaranteed to be unique as long as {@link #isValid()} is true.
 * 
 * @author Tobias J�ttner
 */
public class LcnAddrGrp extends LcnAddr implements Comparable<LcnAddrMod> {

    /** The group id. */
    private final int grpId;

    /** Constructs an empty / invalid group address. */
    public LcnAddrGrp() {
        this.grpId = -1; // Invalid
    }

    /**
     * Constructs a group address with (logical) segment id and group id.
     * 
     * @param segId the segment id
     * @param grpId the group id
     */
    public LcnAddrGrp(int segId, int grpId) {
        super(segId);
        this.grpId = grpId;
    }

    /**
     * Gets the group id.
     * 
     * @return the group id
     */
    public int getGrpId() {
        return this.grpId;
    }

    /** {@inheritDoc} */
    @Override
    public boolean isValid() {
        // segId:
        // 0 = Local, 1..2 = Not allowed (but "seen in the wild")
        // 3 = Broadcast, 4 = Status messages, 5..127, 128 = Segment-bus disabled (valid value)
        // grpId:
        // 3 = Broadcast, 4 = Status messages, 5..254
        return this.segId >= 0 && this.segId <= 128 && this.grpId >= 3 && this.grpId <= 254;
    }

    /** {@inheritDoc} */
    @Override
    public boolean isGroup() {
        return true;
    }

    /** {@inheritDoc} */
    @Override
    public int getId() {
        return this.grpId;
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        // Reversing the bits helps to generate better balanced trees as ids tend to be "user-sorted"
        try {
            if (this.isValid()) {
                return ReverseNumber.reverseUInt8(this.grpId) << 8 + ReverseNumber.reverseUInt8(this.segId);
            }
        } catch (IllegalArgumentException ex) {
        }
        return -1;
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof LcnAddrGrp)) {
            return false;
        }
        return this.segId == ((LcnAddrGrp) obj).segId && this.grpId == ((LcnAddrGrp) obj).grpId;
    }

    /** {@inheritDoc} */
    @Override
    public int compareTo(LcnAddrMod other) {
        return this.hashCode() - other.hashCode();
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return this.isValid() ? String.format("S%03dG%03d", this.segId, this.grpId) : "Invalid";
    }

}