jackcess/src/java/com/healthmarketscience/jackcess/RowId.java

/*
Copyright (c) 2007 Health Market Science, Inc.

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., 59 Temple Place, Suite 330, Boston, MA  02111-1307
USA

You can contact Health Market Science at info@healthmarketscience.com
or at the following address:

Health Market Science
2700 Horizon Drive
Suite 200
King of Prussia, PA 19406
*/

package com.healthmarketscience.jackcess;

import org.apache.commons.lang.builder.CompareToBuilder;


/**
 * Uniquely identifies a row of data within the access database.
 *
 * @author James Ahlborn
 */
public class RowId implements Comparable<RowId>
{
  /** special page number which will sort before any other valid page
      number */
  public static final int FIRST_PAGE_NUMBER = -1;
  /** special page number which will sort after any other valid page
      number */
  public static final int LAST_PAGE_NUMBER = -2;

  /** special row number representing an invalid row number */
  public static final int INVALID_ROW_NUMBER = -1;

  /** type attributes for RowIds which simplify comparisons */
  public enum Type {
    /** comparable type indicating this RowId should always compare less than
        normal RowIds */
    ALWAYS_FIRST,
    /** comparable type indicating this RowId should always compare
        normally */
    NORMAL,
    /** comparable type indicating this RowId should always compare greater
        than normal RowIds */
    ALWAYS_LAST;
  }
  
  /** special rowId which will sort before any other valid rowId */
  public static final RowId FIRST_ROW_ID = new RowId(
      FIRST_PAGE_NUMBER, INVALID_ROW_NUMBER);

  /** special rowId which will sort after any other valid rowId */
  public static final RowId LAST_ROW_ID = new RowId(
      LAST_PAGE_NUMBER, INVALID_ROW_NUMBER);

  private final int _pageNumber;
  private final int _rowNumber;
  private final Type _type;
  
  /**
   * Creates a new <code>RowId</code> instance.
   *
   */
  public RowId(int pageNumber,int rowNumber) {
    _pageNumber = pageNumber;
    _rowNumber = rowNumber;
    _type = ((_pageNumber == FIRST_PAGE_NUMBER) ? Type.ALWAYS_FIRST :
             ((_pageNumber == LAST_PAGE_NUMBER) ? Type.ALWAYS_LAST :
              Type.NORMAL));
  }

  public int getPageNumber() {
    return _pageNumber;
  }

  public int getRowNumber() {
    return _rowNumber;
  }

  /**
   * Returns {@code true} if this rowId potentially represents an actual row
   * of data, {@code false} otherwise.
   */
  public boolean isValid() {
    return((getRowNumber() >= 0) && (getPageNumber() >= 0));
  }

  public Type getType() {
    return _type;
  }
  
  public int compareTo(RowId other) {
    return new CompareToBuilder()
      .append(getType(), other.getType())
      .append(getPageNumber(), other.getPageNumber())
      .append(getRowNumber(), other.getRowNumber())
      .toComparison();
  }

  @Override
  public int hashCode() {
    return getPageNumber() ^ getRowNumber();
  }

  @Override
  public boolean equals(Object o) {
    return ((this == o) ||
            ((o != null) && (getClass() == o.getClass()) &&
             (getPageNumber() == ((RowId)o).getPageNumber()) &&
             (getRowNumber() == ((RowId)o).getRowNumber())));
  }
  
  @Override
  public String toString() {
    return getPageNumber() + ":" + getRowNumber();
  }
  
}