os/dtrace/AggregationRecord.java

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
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/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * ident	"%Z%%M%	%I%	%E% SMI"
 */
package org.opensolaris.os.dtrace;

import java.util.*;
import java.io.*;
import java.beans.*;

/**
 * A single key-value pair in a DTrace aggregation.
 * <p>
 * Immutable.  Supports persistence using {@link java.beans.XMLEncoder}.
 *
 * @see Aggregation
 * @author Tom Erickson
 */
public final class AggregationRecord implements Record, Serializable {
    static final long serialVersionUID = -4367614268579702616L;

    static {
	try {
	    BeanInfo info = Introspector.getBeanInfo(AggregationRecord.class);
	    PersistenceDelegate persistenceDelegate =
		    new DefaultPersistenceDelegate(
		    new String[] {"tuple", "value", "ordinal"})
	    {
		/*
		 * Need to prevent DefaultPersistenceDelegate from using
		 * overridden equals() method, resulting in a
		 * StackOverFlowError.  Revert to PersistenceDelegate
		 * implementation.  See
		 * http://forum.java.sun.com/thread.jspa?threadID=
		 * 477019&tstart=135
		 */
		protected boolean
		mutatesTo(Object oldInstance, Object newInstance)
		{
		    return (newInstance != null && oldInstance != null &&
			    oldInstance.getClass() == newInstance.getClass());
		}
	    };
	    BeanDescriptor d = info.getBeanDescriptor();
	    d.setValue("persistenceDelegate", persistenceDelegate);
	} catch (IntrospectionException e) {
	    System.out.println(e);
	}
    }

    /** @serial */
    private Tuple tuple;
    /** @serial */
    private AggregationValue value;
    /** @serial */
    private int ordinal;


    /**
     * Creates an aggregation record with the given key and value.
     * Supports XML persistence.
     *
     * @see #AggregationRecord(Tuple tupleKey, AggregationValue
     * recordValue, int n)
     */
    public
    AggregationRecord(Tuple tupleKey, AggregationValue recordValue)
    {
    //
    // Called by native code, but public to support backwardly
    // compatible XML encoding.
    //
	tuple = tupleKey;
	value = recordValue;
	validate();
    }

    /**
     * Creates an aggregation record with the given key, value, and
     * ordinal. Supports XML persistence.
     *
     * @param tupleKey aggregation tuple, may be empty (see {@link
     * Tuple#EMPTY}) to indicate that this record's value belongs to an
     * unkeyed aggregation declared without square brackets, for
     * example: <pre>		{@code @a = count();}</pre>
     * @param recordValue aggregated value associated with the given
     * tuple
     * @param n ordinal from zero (first) to n-1 (last) within the
     * {@link Aggregate} containing this record
     * @throws NullPointerException if the given key or value is
     * {@code null}
     * @throws IllegalArgumentException if the given ordinal is negative
     */
    public
    AggregationRecord(Tuple tupleKey, AggregationValue recordValue, int n)
    {
	tuple = tupleKey;
	value = recordValue;
	ordinal = n;
	validate();
    }

    private final void
    validate()
    {
	if (tuple == null) {
	    throw new NullPointerException("key is null");
	}
	if (value == null) {
	    throw new NullPointerException("value is null");
	}
	if (ordinal < 0) {
	    throw new IllegalArgumentException("ordinal is negative");
	}
    }

    /**
     * Gets the multi-element key associated with {@link
     * #getValue()}.
     *
     * @return non-null, possibly empty tuple
     * @see Aggregation#getRecord(Tuple key)
     */
    public Tuple
    getTuple()
    {
	return tuple;
    }

    /**
     * Gets the value associated with {@link #getTuple()}.  Values
     * generated by the DTrace actions {@code count()}, {@code sum()},
     * {@code avg()}, {@code min()}, and {@code max()} are of type
     * {@link Long}.  Values generated by the DTrace actions {@code
     * quantize(}) and {@code lquantize()} are of type {@link
     * Distribution}.
     *
     * @return non-null value keyed to {@link #getTuple()}
     */
    public AggregationValue
    getValue()
    {
	return value;
    }

    /**
     * Gets the ordinal generated when this AggregationRecord was added
     * to its containing {@link Aggregate} by the native DTrace library,
     * from zero (first) to n-1 (last). The sequence described by an
     * aggregate's record ordinals reflects the setting of the {@link
     * Option#aggsortkey aggsortkey}, {@link Option#aggsortkeypos
     * aggsortkeypos}, {@link Option#aggsortpos aggsortpos}, and {@link
     * Option#aggsortrev aggsortrev} DTrace options and matches the way
     * that the records would be ordered by {@code dtrace(1M)}.
     *
     * @return non-negative ordinal from zero (first) to n-1 (last)
     * within the {@code Aggregate} containing this record
     * @see Aggregate#getOrderedRecords()
     */
    public int
    getOrdinal()
    {
	return ordinal;
    }

    /**
     * Package level access; called by Aggregate
     */
    void
    setOrdinal(int n)
    {
	if (n < 0) {
	    throw new IllegalArgumentException("ordinal is negative");
	}
	ordinal = n;
    }

    /**
     * Compares the specified object with this aggregation record for
     * equality.  Defines equality as having the same tuple and value.
     *
     * @return {@code true} if and only if the specified object is an
     * {@code AggregationRecord} and both records have equal tuples as
     * defined by {@link Tuple#equals(Object o)} and equal values as
     * defined by the implementation of {@link AggregationValue}
     */
    public boolean
    equals(Object o)
    {
	if (o instanceof AggregationRecord) {
	    AggregationRecord r = (AggregationRecord)o;
	    return (tuple.equals(r.tuple) &&
		    value.equals(r.value));
	}
	return false;
    }

    /**
     * Overridden to ensure that equal records have equal hash codes.
     */
    @Override
    public int
    hashCode()
    {
	int hash = 17;
	hash = (37 * hash) + tuple.hashCode();
	hash = (37 * hash) + value.hashCode();
	return hash;
    }

    private void
    readObject(ObjectInputStream s)
            throws IOException, ClassNotFoundException
    {
	s.defaultReadObject();
	// Check class invariants
	try {
	    validate();
	} catch (Exception e) {
	    InvalidObjectException x = new InvalidObjectException(
		    e.getMessage());
	    x.initCause(e);
	    throw x;
	}
    }

    /**
     * Gets a string representation of this aggregation record useful
     * for logging and not intended for display.  The exact details of
     * the representation are unspecified and subject to change, but the
     * following format may be regarded as typical:
     * <pre><code>
     * class-name[property1 = value1, property2 = value2]
     * </code></pre>
     */
    @Override
    public String
    toString()
    {
	StringBuilder buf = new StringBuilder();
	buf.append(AggregationRecord.class.getName());
	buf.append("[tuple = ");
	buf.append(tuple);
	buf.append(", value = ");
	buf.append(value);
	buf.append(']');
	return buf.toString();
    }
}