package org.apache.lucene.util.encoding;
import java.io.IOException;
import java.io.InputStream;
/*
* 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.
*/
/**
* Decodes data which was encoded by {@link FourFlagsIntEncoder}. Scans
* the <code>indicator</code>, one flag (1-bits) at a time, and decodes extra
* data using {@link VInt8IntDecoder}.
*
* @see FourFlagsIntEncoder
* @lucene.experimental
*/
public class FourFlagsIntDecoder extends IntDecoder {
/**
* Holds all combinations of <i>indicator</i> for fast decoding (saves time
* on real-time bit manipulation)
*/
private final static byte[][] decodeTable = new byte[256][4];
/** Generating all combinations of <i>indicator</i> into separate flags. */
static {
for (int i = 256; i != 0;) {
--i;
for (int j = 4; j != 0;) {
--j;
decodeTable[i][j] = (byte) ((i >>> (j << 1)) & 0x3);
}
}
}
private final IntDecoder decoder = new VInt8IntDecoder();
/** The indicator for decoding a chunk of 4 integers. */
private int indicator;
/** Used as an ordinal of 0 - 3, as the decoder decodes chunks of 4 integers. */
private int ordinal = 0;
@Override
public long decode() throws IOException {
// If we've decoded 8 integers, read the next indicator.
if ((ordinal & 0x3) == 0) {
indicator = in.read();
if (indicator < 0) {
return EOS;
}
ordinal = 0;
}
byte decodeVal = decodeTable[indicator][ordinal++];
if (decodeVal == 0) {
// decode the value from the stream.
long decode = decoder.decode();
return decode == EOS ? EOS : decode + 4;
}
return decodeVal;
}
@Override
public void reInit(InputStream in) {
super.reInit(in);
decoder.reInit(in);
ordinal = 0;
indicator = 0;
}
@Override
public String toString() {
return "FourFlags (VInt8)";
}
}