AutoNumberStep.java :  » Database-DBMS » Quadcap-Embeddable-Database » com » quadcap » sql » Java Open Source

package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import java.sql.SQLException;

import com.quadcap.sql.file.BlockFile;
import com.quadcap.sql.file.PageManager;
import com.quadcap.sql.file.RandomAccess;
import com.quadcap.sql.file.RandomAccessInputStream;
import com.quadcap.sql.file.RandomAccessOutputStream;

import com.quadcap.sql.io.ObjectInputStream;
import com.quadcap.sql.io.ObjectOutputStream;
import com.quadcap.sql.io.Extern;

import com.quadcap.sql.types.Value;
import com.quadcap.sql.types.ValueNull;

import com.quadcap.io.CountedInputStream;

import com.quadcap.util.Debug;

/**
 * Log step to record allocations of auto numbers...
 *
 * @author Stan Bailes
 */
public class AutoNumberStep extends LogStep implements Externalizable {
    String        tableName     = null;
    long                                num                     = 0;

    /**
     * Default constructor for serialization
     */
    public AutoNumberStep() {}

    /**
     * Explicit constructor
     */
    public AutoNumberStep(Session session, Table table, long num) {
        super(session);
  this.tableName = table.getName();
        this.num = num;
    }

    /**
     * We don't bother to undo this -- we don't mind gaps.
     */
    public void undo(Session session) throws IOException, SQLException {}

    /**
     * "Redo" keeps the constraint number in sync.  We don't care about
     * the rows for which this was generated, we just need the max number
     * that we ever gave out....
     */
    public void redo(Session session) throws IOException, SQLException {
  Database db = session.getDatabase();
        db.updateTableIdentity(tableName, num);
    }

    
    public void prepare(Session session) throws IOException, SQLException {
    }
    
    public void readExternal(ObjectInput in)
  throws IOException, ClassNotFoundException
    {
  super.readExternal(in);
  this.tableName = (String)in.readObject();
        this.num = in.readLong();
    }
    
    public void writeExternal(ObjectOutput out) throws IOException {
  super.writeExternal(out);
  out.writeObject(tableName);
        out.writeLong(num);
    }

    //#ifdef DEBUG
    public String toString() {
  StringBuffer sb = new StringBuffer(super.toString());
        sb.append(" AutoNumberStep(");
  sb.append(tableName);
  sb.append(',');
  sb.append(num);
  return sb.toString();
    }
    //#endif

    /**
     * Exposed so a careful client can avoid an allocation
     */
    public void setCurrentId(long x) { this.num = x; }

    static Extern extern;
    public void setExtern(Extern extern) { AutoNumberStep.extern = extern; }
    public Extern getExtern() { return extern; }
}