001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.fusesource.hawtbuf.codec;
018    
019    import java.io.DataInput;
020    import java.io.DataOutput;
021    import java.io.IOException;
022    
023    /**
024     * Implementation of a variable length Codec for a signed Integer
025     *
026     */
027    public class VarSignedIntegerCodec extends VarIntegerCodec {
028    
029        public static final VarSignedIntegerCodec INSTANCE = new VarSignedIntegerCodec();
030    
031    
032        public void encode(Integer value, DataOutput dataOut) throws IOException {
033            super.encode(encodeZigZag(value), dataOut);
034        }
035    
036        public Integer decode(DataInput dataIn) throws IOException {
037            return decodeZigZag(super.decode(dataIn));
038        }
039    
040        private static int decodeZigZag(int n) {
041            return (n >>> 1) ^ -(n & 1);
042        }
043    
044        private static int encodeZigZag(int n) {
045            return (n << 1) ^ (n >> 31);
046        }
047    
048        public int estimatedSize(Integer value) {
049            return super.estimatedSize(encodeZigZag(value));
050        }
051    }