/**
* Copyright (C) 2011 the original author or authors.
* See the notice.md file distributed with this work for additional
* information regarding copyright ownership.
*
* 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.iq80.leveldb.table;
import org.iq80.leveldb.util.Slice;
public class BytewiseComparator implements UserComparator
{
@Override
public String name() {
return "leveldb.BytewiseComparator";
}
@Override
public int compare(Slice sliceA, Slice sliceB)
{
return sliceA.compareTo(sliceB);
}
@Override
public Slice findShortestSeparator(
Slice start,
Slice limit)
{
// Find length of common prefix
int sharedBytes = BlockBuilder.calculateSharedBytes(start, limit);
// Do not shorten if one string is a prefix of the other
if (sharedBytes < Math.min(start.length(), limit.length())) {
// if we can add one to the last shared byte without overflow and the two keys differ by more than
// one increment at this location.
int lastSharedByte = start.getUnsignedByte(sharedBytes);
if (lastSharedByte < 0xff && lastSharedByte + 1 < limit.getUnsignedByte(sharedBytes)) {
Slice result = start.copySlice(0, sharedBytes + 1);
result.setByte(sharedBytes, lastSharedByte + 1);
assert (compare(result, limit) < 0) : "start must be less than last limit";
return result;
}
}
return start;
}
@Override
public Slice findShortSuccessor(Slice key)
{
// Find first character that can be incremented
for (int i = 0; i < key.length(); i++) {
int b = key.getUnsignedByte(i);
if (b != 0xff) {
Slice result = key.copySlice(0, i + 1);
result.setByte(i, b +1);
return result;
}
}
// key is a run of 0xffs. Leave it alone.
return key;
}
}