/*
* Copyright (C) 2012, 2016 higherfrequencytrading.com
* Copyright (C) 2016 Roman Leventov
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License.
*
* This program 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package net.openhft.chronicle.hash.impl;
import net.openhft.chronicle.core.Maths;
import net.openhft.chronicle.hash.serialization.impl.EnumMarshallable;
import net.openhft.chronicle.wire.Marshallable;
import net.openhft.chronicle.wire.WireIn;
import net.openhft.chronicle.wire.WireOut;
import org.jetbrains.annotations.NotNull;
import static net.openhft.chronicle.core.Maths.isPowerOf2;
public interface HashSplitting extends Marshallable {
static HashSplitting forSegments(int segments) {
assert segments > 0;
if (segments == 1)
return ForSingleSegment.INSTANCE;
if (isPowerOf2(segments))
return new ForPowerOf2Segments(segments);
return new ForNonPowerOf2Segments(segments);
}
int segmentIndex(long hash);
long segmentHash(long hash);
final class ForSingleSegment implements HashSplitting, EnumMarshallable<ForSingleSegment> {
public static final ForSingleSegment INSTANCE = new ForSingleSegment();
private ForSingleSegment() {}
@Override
public int segmentIndex(long hash) {
return 0;
}
@Override
public long segmentHash(long hash) {
return hash;
}
@Override
public ForSingleSegment readResolve() {
return INSTANCE;
}
}
class ForPowerOf2Segments implements HashSplitting {
private int bits;
private transient int mask;
ForPowerOf2Segments(int segments) {
assert Maths.isPowerOf2(segments);
bits = Integer.numberOfTrailingZeros(segments);
mask = segments - 1;
}
@Override
public int segmentIndex(long hash) {
return ((int) hash) & mask;
}
@Override
public long segmentHash(long hash) {
return hash >>> bits;
}
@Override
public void readMarshallable(@NotNull WireIn wire) {
bits = wire.read(() -> "bits").int32();
mask = (1 << bits) - 1;
}
@Override
public void writeMarshallable(@NotNull WireOut wire) {
wire.write(() -> "bits").int32(bits);
}
}
//TODO optimize?
class ForNonPowerOf2Segments implements HashSplitting {
private static final int MASK = Integer.MAX_VALUE;
private static final int BITS = 31;
private int segments;
public ForNonPowerOf2Segments(int segments) {
this.segments = segments;
}
@Override
public int segmentIndex(long hash) {
return (((int) hash) & MASK) % segments;
}
@Override
public long segmentHash(long hash) {
return hash >>> BITS;
}
@Override
public void readMarshallable(@NotNull WireIn wire) {
segments = wire.read(() -> "segments").int32();
}
@Override
public void writeMarshallable(@NotNull WireOut wire) {
wire.write(() -> "segments").int32(segments);
}
}
}