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Zero-allocation implementations of fast non-cryptographic hash functions
for byte sequences or blocks of memory
/*
* Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
*
* 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 net.openhft.hashing;
import java.nio.ByteOrder;
import static java.nio.ByteOrder.BIG_ENDIAN;
import static java.nio.ByteOrder.LITTLE_ENDIAN;
public abstract class CharSequenceAccess extends Access {
static CharSequenceAccess charSequenceAccess(ByteOrder order) {
return order == LITTLE_ENDIAN ?
LittleEndianCharSequenceAccess.INSTANCE :
BigEndianCharSequenceAccess.INSTANCE;
}
static CharSequenceAccess nativeCharSequenceAccess() {
return charSequenceAccess(ByteOrder.nativeOrder());
}
private static int ix(long offset) {
return (int) (offset >> 1);
}
protected static long getLong(CharSequence input, long offset,
int char0Off, int char1Off, int char2Off, int char3Off,
int char4Off, int delta) {
final int base = ix(offset);
if (0 == ((int)offset & 1)) {
final long char0 = input.charAt(base + char0Off);
final long char1 = input.charAt(base + char1Off);
final long char2 = input.charAt(base + char2Off);
final long char3 = input.charAt(base + char3Off);
return char0 | (char1 << 16) | (char2 << 32) | (char3 << 48);
} else {
final long char0 = input.charAt(base + char0Off + delta) >>> 8;
final long char1 = input.charAt(base + char1Off + delta);
final long char2 = input.charAt(base + char2Off + delta);
final long char3 = input.charAt(base + char3Off + delta);
final long char4 = input.charAt(base + char4Off);
return char0 | (char1 << 8) | (char2 << 24) | (char3 << 40) | (char4 << 56);
}
}
protected static long getUnsignedInt(CharSequence input, long offset,
int char0Off, int char1Off, int char2Off, int delta) {
final int base = ix(offset);
if (0 == ((int)offset & 1)) {
final long char0 = input.charAt(base + char0Off);
final long char1 = input.charAt(base + char1Off);
return char0 | (char1 << 16);
} else {
final long char0 = input.charAt(base + char0Off + delta) >>> 8;
final long char1 = input.charAt(base + char1Off + delta);
final long char2 = Primitives.unsignedByte(input.charAt(base + char2Off));
return char0 | (char1 << 8) | (char2 << 24);
}
}
protected static char getUnsignedShort(CharSequence input,
long offset, int char1Off, int delta) {
if (0 == ((int)offset & 1)) {
return input.charAt(ix(offset));
} else {
final int base = ix(offset);
final int char0 = input.charAt(base + delta) >>> 8;
final int char1 = input.charAt(base + char1Off);
return (char)(char0 | (char1 << 8));
}
}
protected static int getUnsignedByte(CharSequence input, long offset, int shift) {
return Primitives.unsignedByte(input.charAt(ix(offset)) >> shift);
}
private CharSequenceAccess() {}
@Override
public int getInt(CharSequence input, long offset) {
return (int) getUnsignedInt(input, offset);
}
@Override
public int getShort(CharSequence input, long offset) {
return (int)(short)getUnsignedShort(input, offset);
}
@Override
public int getByte(CharSequence input, long offset) {
return (int) (byte) getUnsignedByte(input, offset);
}
private static class LittleEndianCharSequenceAccess extends CharSequenceAccess {
private static final CharSequenceAccess INSTANCE = new LittleEndianCharSequenceAccess();
private static final Access INSTANCE_REVERSE = Access.newDefaultReverseAccess(INSTANCE);
private LittleEndianCharSequenceAccess() {}
@Override
public long getLong(CharSequence input, long offset) {
return getLong(input, offset, 0, 1, 2, 3, 4, 0);
}
@Override
public long getUnsignedInt(CharSequence input, long offset) {
return getUnsignedInt(input, offset, 0, 1, 2, 0);
}
@Override
public int getUnsignedShort(CharSequence input, long offset) {
return getUnsignedShort(input, offset, 1, 0);
}
@Override
public int getUnsignedByte(CharSequence input, long offset) {
return getUnsignedByte(input, offset, ((int) offset & 1) << 3);
}
@Override
public ByteOrder byteOrder(CharSequence input) {
return LITTLE_ENDIAN;
}
@Override
protected Access reverseAccess() {
return INSTANCE_REVERSE;
}
}
private static class BigEndianCharSequenceAccess extends CharSequenceAccess {
private static final CharSequenceAccess INSTANCE = new BigEndianCharSequenceAccess();
private static final Access INSTANCE_REVERSE = Access.newDefaultReverseAccess(INSTANCE);
private BigEndianCharSequenceAccess() {}
@Override
public long getLong(CharSequence input, long offset) {
return getLong(input, offset, 3, 2, 1, 0, 0, 1);
}
@Override
public long getUnsignedInt(CharSequence input, long offset) {
return getUnsignedInt(input, offset, 1, 0, 0, 1);
}
@Override
public int getUnsignedShort(CharSequence input, long offset) {
return getUnsignedShort(input, offset, 0, 1);
}
@Override
public int getUnsignedByte(CharSequence input, long offset) {
return getUnsignedByte(input, offset, (((int) offset & 1) ^ 1) << 3);
}
@Override
public ByteOrder byteOrder(CharSequence input) {
return BIG_ENDIAN;
}
@Override
protected Access reverseAccess() {
return INSTANCE_REVERSE;
}
}
}