/*
* Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package railo.commons.collection;
import java.util.Random;
import sun.misc.JavaLangAccess;
import sun.misc.SharedSecrets;
/**
* Hashing utilities.
*
* Little endian implementations of Murmur3 hashing.
*/
public class Hashing {
/**
* Static utility methods only.
*/
private Hashing() {
throw new Error("No instances");
}
public static int murmur3_32(byte[] data) {
return murmur3_32(0, data, 0, data.length);
}
public static int murmur3_32(int seed, byte[] data) {
return murmur3_32(seed, data, 0, data.length);
}
@SuppressWarnings("fallthrough")
public static int murmur3_32(int seed, byte[] data, int offset, int len) {
int h1 = seed;
int count = len;
// body
while (count >= 4) {
int k1 = (data[offset] & 0x0FF)
| (data[offset + 1] & 0x0FF) << 8
| (data[offset + 2] & 0x0FF) << 16
| data[offset + 3] << 24;
count -= 4;
offset += 4;
k1 *= 0xcc9e2d51;
k1 = Integer.rotateLeft(k1, 15);
k1 *= 0x1b873593;
h1 ^= k1;
h1 = Integer.rotateLeft(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
}
// tail
if (count > 0) {
int k1 = 0;
switch (count) {
case 3:
k1 ^= (data[offset + 2] & 0xff) << 16;
// fall through
case 2:
k1 ^= (data[offset + 1] & 0xff) << 8;
// fall through
case 1:
k1 ^= (data[offset] & 0xff);
// fall through
default:
k1 *= 0xcc9e2d51;
k1 = Integer.rotateLeft(k1, 15);
k1 *= 0x1b873593;
h1 ^= k1;
}
}
// finalization
h1 ^= len;
// finalization mix force all bits of a hash block to avalanche
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1;
}
public static int murmur3_32(char[] data) {
return murmur3_32(0, data, 0, data.length);
}
public static int murmur3_32(int seed, char[] data) {
return murmur3_32(seed, data, 0, data.length);
}
public static int murmur3_32(int seed, char[] data, int offset, int len) {
int h1 = seed;
int off = offset;
int count = len;
// body
while (count >= 2) {
int k1 = (data[off++] & 0xFFFF) | (data[off++] << 16);
count -= 2;
k1 *= 0xcc9e2d51;
k1 = Integer.rotateLeft(k1, 15);
k1 *= 0x1b873593;
h1 ^= k1;
h1 = Integer.rotateLeft(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
}
// tail
if (count > 0) {
int k1 = data[off];
k1 *= 0xcc9e2d51;
k1 = Integer.rotateLeft(k1, 15);
k1 *= 0x1b873593;
h1 ^= k1;
}
// finalization
h1 ^= len * (Character.SIZE / Byte.SIZE);
// finalization mix force all bits of a hash block to avalanche
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1;
}
public static int murmur3_32(int[] data) {
return murmur3_32(0, data, 0, data.length);
}
public static int murmur3_32(int seed, int[] data) {
return murmur3_32(seed, data, 0, data.length);
}
public static int murmur3_32(int seed, int[] data, int offset, int len) {
int h1 = seed;
int off = offset;
int end = offset + len;
// body
while (off < end) {
int k1 = data[off++];
k1 *= 0xcc9e2d51;
k1 = Integer.rotateLeft(k1, 15);
k1 *= 0x1b873593;
h1 ^= k1;
h1 = Integer.rotateLeft(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
}
// tail (always empty, as body is always 32-bit chunks)
// finalization
h1 ^= len * (Integer.SIZE / Byte.SIZE);
// finalization mix force all bits of a hash block to avalanche
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1;
}
/**
* Holds references to things that can't be initialized until after VM
* is fully booted.
*/
private static class Holder {
/**
* Used for generating per-instance hash seeds.
*
* We try to improve upon the default seeding.
*/
static final Random SEED_MAKER = new Random(
Double.doubleToRawLongBits(Math.random())
^ System.identityHashCode(Hashing.class)
^ System.currentTimeMillis()
^ System.nanoTime()
^ Runtime.getRuntime().freeMemory());
/**
* Access to {@code String.hash32()}
*/
static final JavaLangAccess LANG_ACCESS;
static {
LANG_ACCESS = SharedSecrets.getJavaLangAccess();
if (null == LANG_ACCESS) {
throw new Error("Shared secrets not initialized");
}
}
}
public static int randomHashSeed(Object instance) {
int seed;
if (sun.misc.VM.isBooted()) {
seed = Holder.SEED_MAKER.nextInt();
} else {
// lower quality "random" seed value--still better than zero and not
// not practically reversible.
int hashing_seed[] = {
System.identityHashCode(Hashing.class),
System.identityHashCode(instance),
System.identityHashCode(Thread.currentThread()),
(int) Thread.currentThread().getId(),
(int) (System.currentTimeMillis() >>> 2), // resolution is poor
(int) (System.nanoTime() >>> 5), // resolution is poor
(int) (Runtime.getRuntime().freeMemory() >>> 4) // alloc min
};
seed = murmur3_32(hashing_seed);
}
// force to non-zero.
return (0 != seed) ? seed : 1;
}
}