objectblockiterator.java

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package cn.js.fan.base;

import org.apache.log4j.Logger;
import java.util.Iterator;
import cn.js.fan.db.PrimaryKey;
import cn.js.fan.db.KeyUnit;
import java.util.HashMap;


public class ObjectBlockIterator implements Iterator {
  public Logger logger = Logger.getLogger(this.getClass().getName());

  ObjectDb objectDb;

  private Object[] infoBlock;
  private int blockID;
  private int blockStart;

  private String query;

  private int startIndex;
  private int currentIndex;
  private int endIndex;

  private Object previousElement = null;
  private Object nextElement = null;

  
  public ObjectBlockIterator(ObjectDb objectDb, Object[] block, String query,
                              int startIndex, int endIndex) {
    this.objectDb = objectDb;
    this.infoBlock = block;
    this.blockID = startIndex / objectDb.getBlockSize();
    this.blockStart = blockID * objectDb.getBlockSize();
    this.query = query;
    this.currentIndex = startIndex - 1;
    this.startIndex = startIndex;
    this.endIndex = endIndex;
  }

  public void remove() {}

  public boolean hasNext() {
    
    if (currentIndex == endIndex) {
      return false;
    }
    
    
    
    if (nextElement == null) {
      nextElement = getNextElement();
      
      if (nextElement == null) {
        return false;
      }
    }
    return true;
  }

  public boolean hasPrevious() {
    
    if (currentIndex == startIndex) {
      return false;
    }
    
    
    if (previousElement == null) {
      previousElement = getPreviousElement();
      
      if (previousElement == null) {
        return false;
      }
    }
    return true;
  }

  public Object next() throws java.util.NoSuchElementException {
    Object element = null;
    if (nextElement != null) {
      element = nextElement;
      this.nextElement = null;
    }
    else {
      element = getNextElement();
      if (element == null) {
        throw new java.util.NoSuchElementException();
      }
    }
    
    return element;
  }

  public Object previous() {
    Object element = null;
    if (previousElement != null) {
      element = previousElement;
      previousElement = null;
    }
    else {
      element = getPreviousElement();
      if (element == null) {
        throw new java.util.NoSuchElementException();
      }
    }
    return element;
  }

  
  private Object getNextElement() {
    previousElement = null;
    Object element = null;
    if (endIndex!=Integer.MAX_VALUE) { 
      while (currentIndex + 1 < endIndex && element == null) {
        currentIndex++;
        element = getElement(currentIndex);
        
      }
    }
    else { 
      if (currentIndex + 1 < endIndex) {
        currentIndex++;
        element = getElement(currentIndex);
      }
    }
    
    return element;
  }

  
  private Object getPreviousElement() {
    nextElement = null;

    Object element = null;
    while (currentIndex >= startIndex && element == null) {
      currentIndex--;
      element = getElement(currentIndex);
    }
    return element;
  }

  
  private Object getElement(int index) {
    

    if (index < 0) {
      return null;
    }
    
    
    if (index < blockStart || index >= blockStart + objectDb.getBlockSize()) {
      
      this.infoBlock = objectDb.getObjectBlock(query, index);
      this.blockID = index / objectDb.getBlockSize();
      this.blockStart = blockID * objectDb.getBlockSize();
    }
    Object element = null;
    
    
    int relativeIndex = index % objectDb.getBlockSize();
    
    if (relativeIndex < infoBlock.length) {
      element = objectDb.getObjectDb(infoBlock[relativeIndex]);
      
    }
    return element;
  }

  public void setIndex(ObjectDb obj) {
      
      
      nextElement = null;
      previousElement = null;

      
      Object[] currentBlock;
      for (int i = startIndex; i < endIndex; i++) {
          currentBlock = obj.getObjectBlock(query, i);
          if (currentBlock.length == 0) {
              
              
          }
          int blockID = i / obj.getBlockSize();
          int blockEnd = blockID * obj.getBlockSize() +
                         obj.getBlockSize();
          
          if (startIndex < blockEnd) {
              
              
              for (int j = startIndex % obj.getBlockSize();
                           j < currentBlock.length; j++, i++) {
                  if (comparePrimarKey(obj.getPrimaryKey(), currentBlock[j])) {
                      this.currentIndex = i;
                      return;
                  }
              }
          }
          
          else {
              for (int j = 0; j < currentBlock.length; j++, i++) {
                  if (comparePrimarKey(obj.getPrimaryKey(), currentBlock[j])) {
                      this.currentIndex = i;
                      return;
                  }
              }
          }
      }

  }

  
  public boolean comparePrimarKey(PrimaryKey primaryKey, Object objKey) {
      
      if (primaryKey.getKeyCount() == 1) {
          if (primaryKey.getType() == primaryKey.TYPE_LONG)
              return primaryKey.getLongValue()==((Long)objKey).longValue();
          else if (primaryKey.getType() == primaryKey.TYPE_INT)
              return primaryKey.getIntValue()==((Integer)objKey).intValue();
          else if (primaryKey.getType() == primaryKey.TYPE_STRING)
              return primaryKey.getStrValue().equals(((String)objKey));
      } else if (primaryKey.getType() == primaryKey.TYPE_COMPOUND) { 
          HashMap keys = primaryKey.getKeys();
          Iterator ir = keys.keySet().iterator();
          HashMap ks = (HashMap)objKey;
          while (ir.hasNext()) {
              String keyName = (String) ir.next();
              KeyUnit ku = (KeyUnit) keys.get(keyName);
              KeyUnit ku2 = (KeyUnit)ks.get(keyName);
              if (ku2==null)
                  throw new IllegalArgumentException("The key " + keyName + " is not exists in Primary");
              return ku.getValue().equals(ku2.getValue());
          }
      }
      return false;
  }

}