XidFactoryImpl.java

/**
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 org.apache.aries.transaction.internal;

import javax.transaction.xa.Xid;
import org.apache.geronimo.transaction.manager.XidFactory;
import org.apache.geronimo.transaction.manager.XidImpl;

/**
 * Factory for transaction ids that are ever increasing
 * allowing determination of new transactions
 * The Xid is constructed of two parts:
 * <ol><li>8 byte id (LSB first)</li>
 * <li>base id</li>
 * <ol>
 * can't easily extend geronimo XidFactoryImpl b/c count is private
 */
public class XidFactoryImpl implements XidFactory {
    private final byte[] baseId = new byte[Xid.MAXGTRIDSIZE];
    private final long start = System.currentTimeMillis();
    private long count = start;

    public XidFactoryImpl(byte[] tmId) {
        System.arraycopy(tmId, 0, baseId, 8, tmId.length);
    }

    public Xid createXid() {
        byte[] globalId = (byte[]) baseId.clone();
        long id;
        synchronized (this) {
            id = count++;
        }
        insertLong(id, globalId, 0);
        return new XidImpl(globalId);
    }

    public Xid createBranch(Xid globalId, int branch) {
        byte[] branchId = (byte[]) baseId.clone();
        branchId[0] = (byte) branch;
        branchId[1] = (byte) (branch >>> 8);
        branchId[2] = (byte) (branch >>> 16);
        branchId[3] = (byte) (branch >>> 24);
        insertLong(start, branchId, 4);
        return new XidImpl(globalId, branchId);
    }

    public boolean matchesGlobalId(byte[] globalTransactionId) {
        if (globalTransactionId.length != Xid.MAXGTRIDSIZE) {
            return false;
        }
        for (int i = 8; i < globalTransactionId.length; i++) {
            if (globalTransactionId[i] != baseId[i]) {
                return false;
            }
        }
        // for recovery, only match old transactions
        long id = extractLong(globalTransactionId, 0);
        return (id < start);
    }

    public boolean matchesBranchId(byte[] branchQualifier) {
        if (branchQualifier.length != Xid.MAXBQUALSIZE) {
            return false;
        }
        long id = extractLong(branchQualifier, 4);
        if (id >= start) {
            // newly created branch, not recoverable
            return false;
        }

        for (int i = 12; i < branchQualifier.length; i++) {
            if (branchQualifier[i] != baseId[i]) {
                return false;
            }
        }
        return true;
    }

    public Xid recover(int formatId, byte[] globalTransactionid, byte[] branchQualifier) {
        return new XidImpl(formatId, globalTransactionid, branchQualifier);
    }

    static void insertLong(long value, byte[] bytes, int offset) {
        bytes[offset + 0] = (byte) value;
        bytes[offset + 1] = (byte) (value >>> 8);
        bytes[offset + 2] = (byte) (value >>> 16);
        bytes[offset + 3] = (byte) (value >>> 24);
        bytes[offset + 4] = (byte) (value >>> 32);
        bytes[offset + 5] = (byte) (value >>> 40);
        bytes[offset + 6] = (byte) (value >>> 48);
        bytes[offset + 7] = (byte) (value >>> 56);
    }

    static long extractLong(byte[] bytes, int offset) {
        return (bytes[offset + 0] & 0xff)
                + (((bytes[offset + 1] & 0xff)) << 8)
                + (((bytes[offset + 2] & 0xff)) << 16)
                + (((bytes[offset + 3] & 0xffL)) << 24)
                + (((bytes[offset + 4] & 0xffL)) << 32)
                + (((bytes[offset + 5] & 0xffL)) << 40)
                + (((bytes[offset + 6] & 0xffL)) << 48)
                + (((long) bytes[offset + 7]) << 56);
    }

}