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Fork of https://github.com/airlift/aircompressor (zstd only).
This module is temporary until we get an official release that includes the
ZstdInputStream API (which is already implemented by two different people
but neither PR shows any progress).
/*
* 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 ai.vespa.airlift.zstd;
import static ai.vespa.airlift.zstd.Constants.SIZE_OF_LONG;
import static ai.vespa.airlift.zstd.UnsafeUtil.UNSAFE;
import static java.lang.Long.rotateLeft;
import static java.lang.Math.min;
import static java.lang.String.format;
import static sun.misc.Unsafe.ARRAY_BYTE_BASE_OFFSET;
// forked from https://github.com/airlift/slice
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 static long hash(long seed, Object base, long address, int length)
{
XxHash64 hasher = new XxHash64(seed);
hasher.updateHash(base, address, length);
return hasher.hash();
}
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 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 static String badPositionIndex(long index, long size, String desc)
{
if (index < 0) {
return format("%s (%s) must not be negative", desc, index);
}
else if (size < 0) {
throw new IllegalArgumentException("negative size: " + size);
}
else { // index > size
return format("%s (%s) must not be greater than size (%s)", desc, index, size);
}
}
private static String badPositionIndexes(int start, int end, int size)
{
if (start < 0 || start > size) {
return badPositionIndex(start, size, "start index");
}
if (end < 0 || end > size) {
return badPositionIndex(end, size, "end index");
}
// end < start
return format("end index (%s) must not be less than start index (%s)", end, start);
}
private static void checkPositionIndexes(int start, int end, int size)
{
// Carefully optimized for execution by hotspot
if (start < 0 || end < start || end > size) {
throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
}
}
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 + SIZE_OF_LONG;
hash = updateTail(hash, value);
hash = finalShuffle(hash);
return hash;
}
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;
}
}