averagereader.java

来自「nesC写的heed算法」· Java 代码 · 共 86 行

// $Id: AverageReader.java,v 1.4.4.2 2003/08/18 22:09:44 cssharp Exp $

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package net.tinyos.tinydb;

import net.tinyos.util.ByteOps;

/**
 * Implements reader for AVERAGE aggregate
 *
 * @author Eugene Shvets
 * @version 1.0, October 23, 2002
 *
 * Changed 11.3.2002 to use objects for state.  SRM.
 */
public class AverageReader implements AggregateResultsReader {
    /**
	 * Reads data from the byte array from QueryResultMessage
	 */
    public void read(byte[] data) {
		myState = new AverageData();
		myState.sum = ByteOps.makeInt(data[0], data[1]);
		myState.count = ByteOps.makeInt(data[2], data[3]);
    }
	
	/**
	 * Calculates final value of the aggregate.
	 */
	public void finalizeValue() {
		if (myState.count != 0) myState.value = myState.sum / myState.count;
	}
	
	/**
	 * Returns string representation of the finalized value
	 */
	public String getValue() {
	    if (myState.count != 0) return Integer.toString(myState.value);
	    else return "";
	}
	
	public void copyResultState(AggregateResultsReader reader) {
		if (! (reader instanceof AverageReader)) throw new IllegalArgumentException("Wrong type reader");
		
		AverageReader other = (AverageReader)reader;
		other.myState.sum = myState.sum;
		other.myState.count = myState.count;
		other.myState.value = myState.value;
	}
	
	AverageData myState;

}

class AverageData  {
    int sum = 0;
    int count = 0;
	int value = 0;
}