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Library for efficiently working with heap and off-heap memory
/*
* Licensed 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 io.airlift.slice;
import static io.airlift.slice.JvmUtils.unsafe;
import static io.airlift.slice.Preconditions.checkPositionIndexes;
import static java.lang.Long.rotateLeft;
import static java.lang.Math.min;
import static sun.misc.Unsafe.ARRAY_BYTE_BASE_OFFSET;
public final class XxHash64
{
private static final long PRIME64_1 = 0x9E3779B185EBCA87L;
private static final long PRIME64_2 = 0xC2B2AE3D27D4EB4FL;
private static final long PRIME64_3 = 0x165667B19E3779F9L;
private static final long PRIME64_4 = 0x85EBCA77C2b2AE63L;
private static final long PRIME64_5 = 0x27D4EB2F165667C5L;
private static final long DEFAULT_SEED = 0;
private final long seed;
private static final long BUFFER_ADDRESS = ARRAY_BYTE_BASE_OFFSET;
private final byte[] buffer = new byte[32];
private int bufferSize;
private long bodyLength;
private long v1;
private long v2;
private long v3;
private long v4;
public XxHash64()
{
this(DEFAULT_SEED);
}
public XxHash64(long seed)
{
this.seed = seed;
this.v1 = seed + PRIME64_1 + PRIME64_2;
this.v2 = seed + PRIME64_2;
this.v3 = seed;
this.v4 = seed - PRIME64_1;
}
public XxHash64 update(byte[] data)
{
return update(data, 0, data.length);
}
public XxHash64 update(byte[] data, int offset, int length)
{
checkPositionIndexes(offset, offset + length, data.length);
updateHash(data, ARRAY_BYTE_BASE_OFFSET + offset, length);
return this;
}
public XxHash64 update(Slice data)
{
return update(data, 0, data.length());
}
public XxHash64 update(Slice data, int offset, int length)
{
checkPositionIndexes(0, offset + length, data.length());
updateHash(data.getBase(), data.getAddress() + offset, length);
return this;
}
public long hash()
{
long hash;
if (bodyLength > 0) {
hash = computeBody();
}
else {
hash = seed + PRIME64_5;
}
hash += bodyLength + bufferSize;
return updateTail(hash, buffer, BUFFER_ADDRESS, 0, bufferSize);
}
private long computeBody()
{
long hash = rotateLeft(v1, 1) + rotateLeft(v2, 7) + rotateLeft(v3, 12) + rotateLeft(v4, 18);
hash = update(hash, v1);
hash = update(hash, v2);
hash = update(hash, v3);
hash = update(hash, v4);
return hash;
}
private void updateHash(Object base, long address, int length)
{
if (bufferSize > 0) {
int available = min(32 - bufferSize, length);
unsafe.copyMemory(base, address, buffer, BUFFER_ADDRESS + bufferSize, available);
bufferSize += available;
address += available;
length -= available;
if (bufferSize == 32) {
updateBody(buffer, BUFFER_ADDRESS, bufferSize);
bufferSize = 0;
}
}
if (length >= 32) {
int index = updateBody(base, address, length);
address += index;
length -= index;
}
if (length > 0) {
unsafe.copyMemory(base, address, buffer, BUFFER_ADDRESS, length);
bufferSize = length;
}
}
private int updateBody(Object base, long address, int length)
{
int remaining = length;
while (remaining >= 32) {
v1 = mix(v1, unsafe.getLong(base, address));
v2 = mix(v2, unsafe.getLong(base, address + 8));
v3 = mix(v3, unsafe.getLong(base, address + 16));
v4 = mix(v4, unsafe.getLong(base, address + 24));
address += 32;
remaining -= 32;
}
int index = length - remaining;
bodyLength += index;
return index;
}
public static long hash(long value)
{
long hash = DEFAULT_SEED + PRIME64_5 + SizeOf.SIZE_OF_LONG;
hash = updateTail(hash, value);
hash = finalShuffle(hash);
return hash;
}
public static long hash(Slice data)
{
return hash(data, 0, data.length());
}
public static long hash(long seed, Slice data)
{
return hash(seed, data, 0, data.length());
}
public static long hash(Slice data, int offset, int length)
{
return hash(DEFAULT_SEED, data, offset, length);
}
public static long hash(long seed, Slice data, int offset, int length)
{
checkPositionIndexes(0, offset + length, data.length());
Object base = data.getBase();
final long address = data.getAddress() + offset;
long hash;
if (length >= 32) {
hash = updateBody(seed, base, address, length);
}
else {
hash = seed + PRIME64_5;
}
hash += length;
// round to the closest 32 byte boundary
// this is the point up to which updateBody() processed
int index = length & 0xFFFFFFE0;
return updateTail(hash, base, address, index, length);
}
private static long updateTail(long hash, Object base, long address, int index, int length)
{
while (index <= length - 8) {
hash = updateTail(hash, unsafe.getLong(base, address + index));
index += 8;
}
if (index <= length - 4) {
hash = updateTail(hash, unsafe.getInt(base, address + index));
index += 4;
}
while (index < length) {
hash = updateTail(hash, unsafe.getByte(base, address + index));
index++;
}
hash = finalShuffle(hash);
return hash;
}
private static long updateBody(long seed, Object base, long address, int length)
{
long v1 = seed + PRIME64_1 + PRIME64_2;
long v2 = seed + PRIME64_2;
long v3 = seed;
long v4 = seed - PRIME64_1;
int remaining = length;
while (remaining >= 32) {
v1 = mix(v1, unsafe.getLong(base, address));
v2 = mix(v2, unsafe.getLong(base, address + 8));
v3 = mix(v3, unsafe.getLong(base, address + 16));
v4 = mix(v4, unsafe.getLong(base, address + 24));
address += 32;
remaining -= 32;
}
long hash = rotateLeft(v1, 1) + rotateLeft(v2, 7) + rotateLeft(v3, 12) + rotateLeft(v4, 18);
hash = update(hash, v1);
hash = update(hash, v2);
hash = update(hash, v3);
hash = update(hash, v4);
return hash;
}
private static long mix(long current, long value)
{
return rotateLeft(current + value * PRIME64_2, 31) * PRIME64_1;
}
private static long update(long hash, long value)
{
long temp = hash ^ mix(0, value);
return temp * PRIME64_1 + PRIME64_4;
}
private static long updateTail(long hash, long value)
{
long temp = hash ^ mix(0, value);
return rotateLeft(temp, 27) * PRIME64_1 + PRIME64_4;
}
private static long updateTail(long hash, int value)
{
long unsigned = value & 0xFFFF_FFFFL;
long temp = hash ^ (unsigned * PRIME64_1);
return rotateLeft(temp, 23) * PRIME64_2 + PRIME64_3;
}
private static long updateTail(long hash, byte value)
{
int unsigned = value & 0xFF;
long temp = hash ^ (unsigned * PRIME64_5);
return rotateLeft(temp, 11) * PRIME64_1;
}
private static long finalShuffle(long hash)
{
hash ^= hash >>> 33;
hash *= PRIME64_2;
hash ^= hash >>> 29;
hash *= PRIME64_3;
hash ^= hash >>> 32;
return hash;
}
}
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