/*****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
****************************************************************/
package org.apache.cayenne.util;
/**
* Assists in implementing {@link Object#hashCode()} methods. The code is based on
* HashCodeBuilder from commons-lang 2.1.
*
* @since 3.0
*/
public class HashCodeBuilder {
/**
* Constant to use in building the hashCode.
*/
private final int iConstant;
/**
* Running total of the hashCode.
*/
private int iTotal = 0;
/**
* <p>
* Uses two hard coded choices for the constants needed to build a
* <code>hashCode</code>.
* </p>
*/
public HashCodeBuilder() {
iConstant = 37;
iTotal = 17;
}
/**
* <p>
* Two randomly chosen, non-zero, odd numbers must be passed in. Ideally these should
* be different for each class, however this is not vital.
* </p>
* <p>
* Prime numbers are preferred, especially for the multiplier.
* </p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @throws IllegalArgumentException if the number is zero or even
*/
public HashCodeBuilder(int initialNonZeroOddNumber, int multiplierNonZeroOddNumber) {
if (initialNonZeroOddNumber == 0) {
throw new IllegalArgumentException(
"HashCodeBuilder requires a non zero initial value");
}
if (initialNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException(
"HashCodeBuilder requires an odd initial value");
}
if (multiplierNonZeroOddNumber == 0) {
throw new IllegalArgumentException(
"HashCodeBuilder requires a non zero multiplier");
}
if (multiplierNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException(
"HashCodeBuilder requires an odd multiplier");
}
iConstant = multiplierNonZeroOddNumber;
iTotal = initialNonZeroOddNumber;
}
/**
* <p>
* Adds the result of super.hashCode() to this builder.
* </p>
*
* @param superHashCode the result of calling <code>super.hashCode()</code>
* @return this HashCodeBuilder, used to chain calls.
* @since 2.0
*/
public HashCodeBuilder appendSuper(int superHashCode) {
iTotal = iTotal * iConstant + superHashCode;
return this;
}
// -------------------------------------------------------------------------
/**
* <p>
* Append a <code>hashCode</code> for an <code>Object</code>.
* </p>
*
* @param object the Object to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(Object object) {
if (object == null) {
iTotal = iTotal * iConstant;
}
else {
if (object.getClass().isArray() == false) {
// the simple case, not an array, just the element
iTotal = iTotal * iConstant + object.hashCode();
}
else {
// 'Switch' on type of array, to dispatch to the correct handler
// This handles multi dimensional arrays
if (object instanceof long[]) {
append((long[]) object);
}
else if (object instanceof int[]) {
append((int[]) object);
}
else if (object instanceof short[]) {
append((short[]) object);
}
else if (object instanceof char[]) {
append((char[]) object);
}
else if (object instanceof byte[]) {
append((byte[]) object);
}
else if (object instanceof double[]) {
append((double[]) object);
}
else if (object instanceof float[]) {
append((float[]) object);
}
else if (object instanceof boolean[]) {
append((boolean[]) object);
}
else {
// Not an array of primitives
append((Object[]) object);
}
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>long</code>.
* </p>
*
* @param value the long to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(long value) {
iTotal = iTotal * iConstant + ((int) (value ^ (value >> 32)));
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>int</code>.
* </p>
*
* @param value the int to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(int value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>short</code>.
* </p>
*
* @param value the short to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(short value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>char</code>.
* </p>
*
* @param value the char to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(char value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>byte</code>.
* </p>
*
* @param value the byte to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(byte value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>double</code>.
* </p>
*
* @param value the double to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(double value) {
return append(Double.doubleToLongBits(value));
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>float</code>.
* </p>
*
* @param value the float to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(float value) {
iTotal = iTotal * iConstant + Float.floatToIntBits(value);
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>boolean</code>.
* </p>
* <p>
* This adds <code>iConstant * 1</code> to the <code>hashCode</code> and not a
* <code>1231</code> or <code>1237</code> as done in java.lang.Boolean. This is in
* accordance with the <i>Effective Java</i> design.
* </p>
*
* @param value the boolean to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(boolean value) {
iTotal = iTotal * iConstant + (value ? 0 : 1);
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>Object</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(Object[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>long</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(long[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for an <code>int</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(int[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>short</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(short[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>char</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(char[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>byte</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(byte[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>double</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(double[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>float</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(float[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Append a <code>hashCode</code> for a <code>boolean</code> array.
* </p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeBuilder append(boolean[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
}
else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>
* Return the computed <code>hashCode</code>.
* </p>
*
* @return <code>hashCode</code> based on the fields appended
*/
public int toHashCode() {
return iTotal;
}
}