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/*******************************************************************************
* Copyright (c) 2013 École Polytechnique de Montréal
*
* All rights reserved. This program and the accompanying materials are made
* available under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Geneviève Bastien - Initial implementation and API
*******************************************************************************/
package org.eclipse.linuxtools.tmf.core.synchronization;
import java.io.Serializable;
import java.math.BigDecimal;
import java.math.MathContext;
import org.eclipse.linuxtools.tmf.core.timestamp.ITmfTimestamp;
import org.eclipse.linuxtools.tmf.core.timestamp.TmfTimestamp;
/**
* Class implementing a linear timestamp transform, with a slope and/or offset
*
* f(t) = alpha*t + beta
*
* @author Geneviève Bastien
* @since 3.0
*/
public class TmfTimestampTransformLinear implements ITmfTimestampTransform, Serializable {
/**
* Generated serial UID
*/
private static final long serialVersionUID = -4756608071358979461L;
/**
* Respectively the slope and offset and this linear equation.
*
* FIXME: Maybe doubles will be enough, for the whole synchronization
* package as well, I think BigDecimal is a remnant of past trials and
* errors
*/
private final BigDecimal fAlpha;
private final BigDecimal fBeta;
private static final MathContext fMc = MathContext.DECIMAL128;
/**
* Default constructor
*/
public TmfTimestampTransformLinear() {
fAlpha = BigDecimal.ONE;
fBeta = BigDecimal.ZERO;
}
/**
* Constructor with alpha and beta
*
* @param alpha
* The slope of the linear transform
* @param beta
* The initial offset of the linear transform
*/
public TmfTimestampTransformLinear(final double alpha, final double beta) {
fAlpha = BigDecimal.valueOf(alpha);
fBeta = BigDecimal.valueOf(beta);
}
/**
* Constructor with alpha and beta in big decimal
*
* @param fAlpha2
* The slope of the linear transform
* @param fBeta2
* The initial offset of the linear transform
*/
public TmfTimestampTransformLinear(final BigDecimal fAlpha2, final BigDecimal fBeta2) {
if (fAlpha2 != null) {
fAlpha = fAlpha2;
} else {
fAlpha = BigDecimal.ONE;
}
if (fBeta2 != null) {
fBeta = fBeta2;
} else {
fBeta = BigDecimal.ZERO;
}
}
@Override
public ITmfTimestamp transform(ITmfTimestamp timestamp) {
BigDecimal newvalue = BigDecimal.valueOf(timestamp.getValue()).multiply(fAlpha, fMc).add(fBeta);
return new TmfTimestamp(timestamp, newvalue.longValue());
}
@Override
public long transform(long timestamp) {
BigDecimal t = BigDecimal.valueOf(timestamp).multiply(fAlpha, fMc).add(fBeta);
return t.longValue();
}
@Override
public ITmfTimestampTransform composeWith(ITmfTimestampTransform composeWith) {
if (composeWith.equals(TmfTimestampTransform.IDENTITY)) {
/* If composing with identity, just return this */
return this;
} else if (composeWith instanceof TmfTimestampTransformLinear) {
/* If composeWith is a linear transform, add the two together */
TmfTimestampTransformLinear ttl = (TmfTimestampTransformLinear) composeWith;
BigDecimal newAlpha = fAlpha.multiply(ttl.fAlpha, fMc);
BigDecimal newBeta = fAlpha.multiply(ttl.fBeta, fMc).add(fBeta);
return new TmfTimestampTransformLinear(newAlpha, newBeta);
} else {
/*
* We do not know what to do with this kind of transform, just
* return this
*/
return this;
}
}
@Override
public boolean equals(Object other) {
boolean result = false;
if (other instanceof TmfTimestampTransformLinear) {
TmfTimestampTransformLinear that = (TmfTimestampTransformLinear) other;
result = ((that.fAlpha.equals(fAlpha)) && (that.fBeta.equals(fBeta)));
}
return result;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = (prime * result) + (fBeta.multiply(fAlpha).intValue());
return result;
}
@Override
public String toString() {
return "TmfTimestampLinear [ alpha = " + fAlpha.toString() + //$NON-NLS-1$
", beta = " + fBeta.toString() + //$NON-NLS-1$
" ]"; //$NON-NLS-1$
}
}
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