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/*
 *  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.
 *
 *  This code was originally part of the Apache Harmony project.
 *  The Apache Harmony project has been discontinued.
 *  That's why we imported the code into iText.
 */

package com.itextpdf.awt.geom.misc;

/**
 * This class is a convenience method to sequentially calculate hash code of the
 * object based on the field values. The result depends on the order of elements
 * appended. The exact formula is the same as for
 * java.util.List.hashCode.
 * 
 * If you need order independent hash code just summate, multiply or XOR all
 * elements.
 * 
 * 
 * Suppose we have class:
 * 
 * 

 * class Thing {
 *     long id;
 *     String name;
 *     float weight;
 * }
 * 
 * 
 * The hash code calculation can be expressed in 2 forms.
 * 
 * 
 * For maximum performance:
 * 
 * 

 * public int hashCode() {
 *     int hashCode = HashCode.EMPTY_HASH_CODE;
 *     hashCode = HashCode.combine(hashCode, id);
 *     hashCode = HashCode.combine(hashCode, name);
 *     hashCode = HashCode.combine(hashCode, weight);
 *     return hashCode;
 * }
 * 
 * 
 * 
 * For convenience: 
 * public int hashCode() {
 *     return new HashCode().append(id).append(name).append(weight).hashCode();
 * }
 * 
*
* @see java.util.List#hashCode()
*/
public final class HashCode {
/**
* The hashCode value before any data is appended, equals to 1.
* @see java.util.List#hashCode()
*/
public static final int EMPTY_HASH_CODE = 1;
private int hashCode = EMPTY_HASH_CODE;
/**
* Returns accumulated hashCode
*/
public final int hashCode() {
return hashCode;
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, boolean value) {
int v = value ? 1231 : 1237;
return combine(hashCode, v);
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, long value) {
int v = (int) (value ^ (value >>> 32));
return combine(hashCode, v);
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, float value) {
int v = Float.floatToIntBits(value);
return combine(hashCode, v);
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, double value) {
long v = Double.doubleToLongBits(value);
return combine(hashCode, v);
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, Object value) {
return combine(hashCode, value.hashCode());
}
/**
* Combines hashCode of previous elements sequence and value's hashCode.
* @param hashCode previous hashCode value
* @param value new element
* @return combined hashCode
*/
public static int combine(int hashCode, int value) {
return 31 * hashCode + value;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(int value) {
hashCode = combine(hashCode, value);
return this;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(long value) {
hashCode = combine(hashCode, value);
return this;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(float value) {
hashCode = combine(hashCode, value);
return this;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(double value) {
hashCode = combine(hashCode, value);
return this;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(boolean value) {
hashCode = combine(hashCode, value);
return this;
}
/**
* Appends value's hashCode to the current hashCode.
* @param value new element
* @return this
*/
public final HashCode append(Object value) {
hashCode = combine(hashCode, value);
return this;
}
}