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    import java.net.ProtocolException;
023    
024    /**
025     * Implementation of a variable length Codec for an Integer
026     *
027     */
028    public class VarIntegerCodec implements Codec<Integer> {
029    
030        public static final VarIntegerCodec INSTANCE = new VarIntegerCodec();
031    
032        public void encode(Integer x, DataOutput dataOut) throws IOException {
033            int value = x;
034            while (true) {
035                if ((value & ~0x7F) == 0) {
036                    dataOut.writeByte(value);
037                    return;
038                } else {
039                    dataOut.writeByte((value & 0x7F) | 0x80);
040                    value >>>= 7;
041                }
042            }
043        }
044    
045        public Integer decode(DataInput dataIn) throws IOException {
046            byte tmp = dataIn.readByte();
047            if (tmp >= 0) {
048                return (int)tmp;
049            }
050            int result = tmp & 0x7f;
051            if ((tmp = dataIn.readByte()) >= 0) {
052                result |= tmp << 7;
053            } else {
054                result |= (tmp & 0x7f) << 7;
055                if ((tmp = dataIn.readByte()) >= 0) {
056                    result |= tmp << 14;
057                } else {
058                    result |= (tmp & 0x7f) << 14;
059                    if ((tmp = dataIn.readByte()) >= 0) {
060                        result |= tmp << 21;
061                    } else {
062                        result |= (tmp & 0x7f) << 21;
063                        result |= (tmp = dataIn.readByte()) << 28;
064                        if (tmp < 0) {
065                            // Discard upper 32 bits.
066                            for (int i = 0; i < 5; i++) {
067                                if (dataIn.readByte() >= 0)
068                                    return result;
069                            }
070                            throw new ProtocolException("Encountered a malformed variable int");
071                        }
072                    }
073                }
074            }
075            return result;
076        }
077    
078        public int getFixedSize() {
079            return -1;
080        }
081    
082        /**
083         * @return the source object since integers are immutable.
084         */
085        public Integer deepCopy(Integer source) {
086            return source;
087        }
088    
089        public boolean isDeepCopySupported() {
090            return true;
091        }
092    
093        public boolean isEstimatedSizeSupported() {
094            return true;
095        }
096    
097        public int estimatedSize(Integer x) {
098            int value = x;
099            if ((value & (0xffffffff << 7)) == 0)
100                return 1;
101            if ((value & (0xffffffff << 14)) == 0)
102                return 2;
103            if ((value & (0xffffffff << 21)) == 0)
104                return 3;
105            if ((value & (0xffffffff << 28)) == 0)
106                return 4;
107            return 5;
108        }
109    }