/* * 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.phoenix.util; import java.io.DataOutput; import java.io.IOException; import org.apache.hadoop.hbase.io.ImmutableBytesWritable; import org.apache.hadoop.hbase.util.Bytes; import org.apache.hadoop.io.WritableUtils; /** * * Prefix encoder for byte arrays. For decoding, see {@link PrefixByteDecoder}. * */ public class PrefixByteEncoder { private int maxLength; private final ImmutableBytesWritable previous = new ImmutableBytesWritable(ByteUtil.EMPTY_BYTE_ARRAY); public PrefixByteEncoder() { } /** * Resets the state of the encoder to its initial state (i.e. forgetting * the previous byte array that may have been encoded). */ public void reset() { previous.set(ByteUtil.EMPTY_BYTE_ARRAY); } /** * @return the maximum length byte array encountered while encoding */ public int getMaxLength() { return maxLength; } /** * Prefix encodes the byte array pointed to into the output stream * @param out output stream to encode into * @param ptr pointer to byte array to encode. * @throws IOException */ public void encode(DataOutput out, ImmutableBytesWritable ptr) throws IOException { encode(out, ptr.get(), ptr.getOffset(), ptr.getLength()); } /** * Prefix encodes the byte array into the output stream * @param out output stream to encode into * @param b byte array to encode * @throws IOException */ public void encode(DataOutput out, byte[] b) throws IOException { encode(out, b, 0, b.length); } /** * Prefix encodes the byte array from offset to length into output stream. * Instead of writing the entire byte array, only the portion of the byte array * that differs from the beginning of the previous byte array written is written. * * @param out output stream to encode into * @param b byte array buffer * @param offset offset into byte array to start encoding * @param length length of byte array to encode * @throws IOException */ public void encode(DataOutput out, byte[] b, int offset, int length) throws IOException { int i = 0; int prevOffset = previous.getOffset(); byte[] prevBytes = previous.get(); int prevLength = previous.getLength(); int minLength = prevLength < b.length ? prevLength : b.length; for(i = 0; (i < minLength) && (prevBytes[prevOffset + i] == b[offset + i]); i++); WritableUtils.writeVInt(out, i); Bytes.writeByteArray(out, b, offset + i, length - i); previous.set(b, offset, length); if (length > maxLength) { maxLength = length; } } }