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Handful shortcuts for Java programming, Java 7 compatible.
/*
* Copyright (C) 2010-2014, Danilo Pianini and contributors
* listed in the project's pom.xml file.
*
* This file is part of Alchemist, and is distributed under the terms of
* the GNU General Public License, with a linking exception, as described
* in the file LICENSE in the Alchemist distribution's top directory.
*/
package org.danilopianini.lang;
import static org.danilopianini.lang.Constants.DJB2_MAGIC;
import static org.danilopianini.lang.Constants.DJB2_SHIFT;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Objects;
import org.danilopianini.io.FileUtilities;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;
/**
* @author Danilo Pianini
*
*/
public final class HashUtils {
private static final HashFunction MURMUR32 = Hashing.murmur3_32();
private static final Charset CHARSET = StandardCharsets.UTF_16;
private static final int MASK_BYTE = 0xff;
private static final int SHIFT3 = 24;
private static final int SHIFT4 = 32;
private static final int SHIFT5 = 40;
private static final int SHIFT6 = 48;
private static final int SHIFT7 = 56;
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final double data) {
return MURMUR32.hashLong(Double.doubleToRawLongBits(data)).asInt();
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final long data) {
return MURMUR32.hashLong(data).asInt();
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final float data) {
return MURMUR32.hashInt(Float.floatToRawIntBits(data)).asInt();
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final CharSequence data) {
return MURMUR32.hashString(data, CHARSET).asInt();
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final Integer data) {
return data;
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final Float data) {
return hash32(data.floatValue());
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final Double data) {
return hash32(data.doubleValue());
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final Long data) {
return hash32(data.longValue());
}
/**
* Computes a 32bit hash.
*
* @param data
* the data to hash
* @return a 32bit hash
*/
public static int hash32(final Object... data) {
final Hasher h = MURMUR32.newHasher();
if (data.length == 1) {
populateHasher(data[0], h);
} else {
populateHasher(data, h);
}
return h.hash().asInt();
}
private static void populateHasher(final Object data, final Hasher h) {
if (data != null) {
if (data instanceof Number) {
final Number d = (Number) data;
if (data instanceof Integer) {
h.putInt(d.intValue());
} else if (data instanceof Double) {
h.putDouble(d.doubleValue());
} else if (data instanceof Long) {
h.putLong(d.longValue());
} else if (data instanceof Float) {
h.putFloat(d.floatValue());
} else if (data instanceof Byte) {
h.putByte(d.byteValue());
} else if (data instanceof Short) {
h.putShort(d.shortValue());
} else {
h.putInt(data.hashCode());
}
} else if (data instanceof CharSequence) {
h.putString((CharSequence) data, CHARSET);
} else if (data.getClass().isArray()) {
final int size = Array.getLength(data);
for (int i = 0; i < size; i++) {
populateHasher(Array.get(data, i), h);
}
} else if (data instanceof Iterable) {
for (final Object o: (Iterable) data) {
populateHasher(o, h);
}
} else if (data instanceof Serializable) {
h.putBytes(FileUtilities.serializeObject((Serializable) data));
} else {
h.putInt(data.hashCode());
}
}
}
/**
* @param bytes
* bytes
* @return DJB2 32bit hash
*/
public static int djb2int32(final byte... bytes) {
int hash32 = Constants.DJB2_START;
for (final byte b : bytes) {
hash32 = hash32 * DJB2_MAGIC ^ b;
}
return hash32;
}
/**
* @param bytes
* bytes
* @return DJB2 32bit hash
*/
public static int djb2int32(final double... bytes) {
return djb2int32(toByta(bytes));
}
/**
* @param bytes
* bytes
* @return DJB2 32bit hash
*/
public static int djb2int32(final int... bytes) {
return djb2int32(toByta(bytes));
}
/**
* @param bytes
* bytes
* @return DJB2 32bit hash
*/
public static int djb2int32obj(final Serializable... bytes) {
return djb2int32(FileUtilities.serializeObject(bytes));
}
/**
* @param bytes
* bytes
* @return DJB2 64bit hash
*/
public static long djb2long64(final byte... bytes) {
long hash = Constants.DJB2_START;
for (final byte b : bytes) {
hash = ((hash << DJB2_SHIFT) + hash) + b;
}
return hash;
}
/**
* @param bytes
* bytes
* @return DJB2 64bit hash
*/
public static long djb2long64(final double... bytes) {
return djb2long64(toByta(bytes));
}
/**
* @param bytes
* bytes
* @return DJB2 64bit hash
*/
public static long djb2long64(final int... bytes) {
return djb2long64(toByta(bytes));
}
/**
* @param bytes
* bytes
* @return DJB2 64bit hash
*/
public static long djb2long64obj(final Serializable... bytes) {
return djb2long64(FileUtilities.serializeObject(bytes));
}
/**
* @param data
* double
* @return byte[]
*/
public static byte[] toByta(final double data) {
return toByta(Double.doubleToRawLongBits(data));
}
/**
* @param data
* double[]
* @return byte[]
*/
public static byte[] toByta(final double[] data) {
Objects.requireNonNull(data);
final byte[] byts = new byte[data.length * 8];
for (int i = 0; i < data.length; i++) {
System.arraycopy(toByta(data[i]), 0, byts, i * 8, 8);
}
return byts;
}
/**
* @param data
* float
* @return byte[]
*/
public static byte[] toByta(final float data) {
return toByta(Float.floatToRawIntBits(data));
}
/**
* @param data
* float[]
* @return byte[]
*/
public static byte[] toByta(final float[] data) {
Objects.requireNonNull(data);
final byte[] byts = new byte[data.length * 4];
for (int i = 0; i < data.length; i++) {
System.arraycopy(toByta(data[i]), 0, byts, i * 4, 4);
}
return byts;
}
/**
* @param data
* int
* @return byte[]
*/
public static byte[] toByta(final int data) {
return new byte[] { (byte) ((data >> SHIFT3) & MASK_BYTE), (byte) ((data >> 16) & MASK_BYTE),
(byte) ((data >> 8) & MASK_BYTE), (byte) ((data >> 0) & MASK_BYTE), };
}
/**
* @param data
* int[]
* @return byte[]
*/
public static byte[] toByta(final int[] data) {
Objects.requireNonNull(data);
final byte[] byts = new byte[data.length * 4];
for (int i = 0; i < data.length; i++) {
System.arraycopy(toByta(data[i]), 0, byts, i * 4, 4);
}
return byts;
}
/**
* @param data
* long
* @return byte[]
*/
public static byte[] toByta(final long data) {
return new byte[] { (byte) ((data >> SHIFT7) & MASK_BYTE), (byte) ((data >> SHIFT6) & MASK_BYTE),
(byte) ((data >> SHIFT5) & MASK_BYTE), (byte) ((data >> SHIFT4) & MASK_BYTE),
(byte) ((data >> SHIFT3) & MASK_BYTE), (byte) ((data >> 16) & MASK_BYTE), (byte) ((data >> 8) & MASK_BYTE),
(byte) ((data >> 0) & MASK_BYTE), };
}
/**
* @param data
* long[]
* @return byte[]
*/
public static byte[] toByta(final long[] data) {
Objects.requireNonNull(data);
final byte[] byts = new byte[data.length * 8];
for (int i = 0; i < data.length; i++) {
System.arraycopy(toByta(data[i]), 0, byts, i * 8, 8);
}
return byts;
}
/**
* Runs System.identityHashCode(a) == System.identityHashCode(b). In most
* JVM implementations, this is actually a pointer comparison. Nevertheless,
* this is not guaranteed: handle with care
*
* @param a
* an {@link Object}
* @param b
* another {@link Object}
* @return System.identityHashCode(a) == System.identityHashCode(b)
*/
public static boolean pointerEquals(final Object a, final Object b) {
return System.identityHashCode(a) == System.identityHashCode(b);
}
/**
*
*/
private HashUtils() {
}
}
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