// Copyright 2017 JanusGraph Authors
//
// 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 org.janusgraph.diskstorage.util;
import com.google.common.hash.HashCode;
import org.janusgraph.diskstorage.StaticBuffer;
/**
* @author Matthias Broecheler (me@matthiasb.com)
*/
public class HashingUtil {
public enum HashLength {
SHORT, LONG;
public int length() {
switch (this) {
case SHORT: return 4;
case LONG: return 8;
default: throw new AssertionError("Unknown hash type: " + this);
}
}
}
private static final StaticBuffer.Factory<HashCode> SHORT_HASH_FACTORY = new StaticBuffer.Factory<HashCode>() {
@Override
public HashCode get(byte[] array, int offset, int limit) {
return HashUtility.SHORT.get().hashBytes(array, offset, limit);
}
};
private static final StaticBuffer.Factory<HashCode> LONG_HASH_FACTORY = new StaticBuffer.Factory<HashCode>() {
@Override
public HashCode get(byte[] array, int offset, int limit) {
return HashUtility.LONG.get().hashBytes(array,offset,limit);
}
};
public static final StaticBuffer hashPrefixKey(final HashLength hashPrefixLen, final StaticBuffer key) {
final int prefixLen = hashPrefixLen.length();
final StaticBuffer.Factory<HashCode> hashFactory;
switch (hashPrefixLen) {
case SHORT:
hashFactory = SHORT_HASH_FACTORY;
break;
case LONG:
hashFactory = LONG_HASH_FACTORY;
break;
default: throw new IllegalArgumentException("Unknown hash prefix: " + hashPrefixLen);
}
HashCode hashcode = key.as(hashFactory);
WriteByteBuffer newKey = new WriteByteBuffer(prefixLen+key.length());
assert prefixLen==4 || prefixLen==8;
if (prefixLen==4) newKey.putInt(hashcode.asInt());
else newKey.putLong(hashcode.asLong());
newKey.putBytes(key);
return newKey.getStaticBuffer();
}
public static final StaticBuffer getKey(final HashLength hashPrefixLen, StaticBuffer hasPrefixedKey) {
return hasPrefixedKey.subrange(hashPrefixLen.length(), hasPrefixedKey.length() - hashPrefixLen.length());
}
}