Imported part of Harmony's awt.geom impl. 6.0-r991881, http://harmony.apache.org/ - Apache License, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0

1 files changed, 203 insertions, 0 deletions

diff --git a/src/org/apache/harmony/misc/HashCode.java b/src/org/apache/harmony/misc/HashCode.java
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+++ b/src/org/apache/harmony/misc/HashCode.java
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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.
+ */
+
+package org.apache.harmony.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
+ * <code>java.util.List.hashCode</code>.
+ * 
+ * If you need order independent hash code just summate, multiply or XOR all
+ * elements.
+ * 
+ * <p>
+ * Suppose we have class:
+ * 
+ * <pre><code>
+ * class Thing {
+ *     long id;
+ *     String name;
+ *     float weight;
+ * }
+ * </code></pre>
+ * 
+ * The hash code calculation can be expressed in 2 forms.
+ * 
+ * <p>
+ * For maximum performance:
+ * 
+ * <pre><code>
+ * 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;
+ * }
+ * </code></pre>
+ * 
+ * <p>
+ * For convenience: <code><pre>
+ * public int hashCode() {
+ *     return new HashCode().append(id).append(name).append(weight).hashCode();
+ * }
+ * </code></pre>
+ * 
+ * @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;
+    }
+}