flink-core/src/main/java/org/apache/flink/api/common/typeutils/base/StringComparator.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.flink.api.common.typeutils.base;

import java.io.IOException;

import org.apache.flink.annotation.Internal;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.types.StringValue;

@Internal
public final class StringComparator extends BasicTypeComparator<String> {

	private static final long serialVersionUID = 1L;
	
	private static final int HIGH_BIT = 0x1 << 7;
	
	private static final int HIGH_BIT2 = 0x1 << 13;
	
	private static final int HIGH_BIT2_MASK = 0x3 << 6;
	
	
	public StringComparator(boolean ascending) {
		super(ascending);
	}

	@Override
	public int compareSerialized(DataInputView firstSource, DataInputView secondSource) throws IOException {
		String s1 = StringValue.readString(firstSource);
		String s2 = StringValue.readString(secondSource);
		int comp = s1.compareTo(s2); 
		return ascendingComparison ? comp : -comp;
	}


	@Override
	public boolean supportsNormalizedKey() {
		return true;
	}


	@Override
	public boolean supportsSerializationWithKeyNormalization() {
		return false;
	}

	@Override
	public int getNormalizeKeyLen() {
		return Integer.MAX_VALUE;
	}

	@Override
	public boolean isNormalizedKeyPrefixOnly(int keyBytes) {
		return true;
	}


	@Override
	public void putNormalizedKey(String record, MemorySegment target, int offset, int len) {;
		final int limit = offset + len;
		final int end = record.length();
		int pos = 0;
		
		while (pos < end && offset < limit) {
			char c = record.charAt(pos++);
			if (c < HIGH_BIT) {
				target.put(offset++, (byte) c);
			}
			else if (c < HIGH_BIT2) {
				target.put(offset++, (byte) ((c >>> 7) | HIGH_BIT));
				if (offset < limit) {
					target.put(offset++, (byte) c);
				}
			}
			else {
				target.put(offset++, (byte) ((c >>> 10) | HIGH_BIT2_MASK));
				if (offset < limit) {
					target.put(offset++, (byte) (c >>> 2));
				}
				if (offset < limit) {
					target.put(offset++, (byte) c);
				}
			}
		}
		while (offset < limit) {
			target.put(offset++, (byte) 0);
		}
	}


	@Override
	public StringComparator duplicate() {
		return new StringComparator(ascendingComparison);
	}
}