/*
 * 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.lucene.util.fst;


import java.io.IOException;

import org.apache.lucene.store.DataInput;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.util.CharsRef;
import org.apache.lucene.util.RamUsageEstimator;

An FST Outputs implementation where each output is a sequence of characters.
@lucene.experimental
/** * An FST {@link Outputs} implementation where each output * is a sequence of characters. * * @lucene.experimental */
public final class CharSequenceOutputs extends Outputs<CharsRef> { private final static CharsRef NO_OUTPUT = new CharsRef(); private final static CharSequenceOutputs singleton = new CharSequenceOutputs(); private CharSequenceOutputs() { } public static CharSequenceOutputs getSingleton() { return singleton; } @Override public CharsRef common(CharsRef output1, CharsRef output2) { assert output1 != null; assert output2 != null; int pos1 = output1.offset; int pos2 = output2.offset; int stopAt1 = pos1 + Math.min(output1.length, output2.length); while(pos1 < stopAt1) { if (output1.chars[pos1] != output2.chars[pos2]) { break; } pos1++; pos2++; } if (pos1 == output1.offset) { // no common prefix return NO_OUTPUT; } else if (pos1 == output1.offset + output1.length) { // output1 is a prefix of output2 return output1; } else if (pos2 == output2.offset + output2.length) { // output2 is a prefix of output1 return output2; } else { return new CharsRef(output1.chars, output1.offset, pos1-output1.offset); } } @Override public CharsRef subtract(CharsRef output, CharsRef inc) { assert output != null; assert inc != null; if (inc == NO_OUTPUT) { // no prefix removed return output; } else if (inc.length == output.length) { // entire output removed return NO_OUTPUT; } else { assert inc.length < output.length: "inc.length=" + inc.length + " vs output.length=" + output.length; assert inc.length > 0; return new CharsRef(output.chars, output.offset + inc.length, output.length-inc.length); } } @Override public CharsRef add(CharsRef prefix, CharsRef output) { assert prefix != null; assert output != null; if (prefix == NO_OUTPUT) { return output; } else if (output == NO_OUTPUT) { return prefix; } else { assert prefix.length > 0; assert output.length > 0; CharsRef result = new CharsRef(prefix.length + output.length); System.arraycopy(prefix.chars, prefix.offset, result.chars, 0, prefix.length); System.arraycopy(output.chars, output.offset, result.chars, prefix.length, output.length); result.length = prefix.length + output.length; return result; } } @Override public void write(CharsRef prefix, DataOutput out) throws IOException { assert prefix != null; out.writeVInt(prefix.length); // TODO: maybe UTF8? for(int idx=0;idx<prefix.length;idx++) { out.writeVInt(prefix.chars[prefix.offset+idx]); } } @Override public CharsRef read(DataInput in) throws IOException { final int len = in.readVInt(); if (len == 0) { return NO_OUTPUT; } else { final CharsRef output = new CharsRef(len); for(int idx=0;idx<len;idx++) { output.chars[idx] = (char) in.readVInt(); } output.length = len; return output; } } @Override public void skipOutput(DataInput in) throws IOException { final int len = in.readVInt(); for(int idx=0;idx<len;idx++) { in.readVInt(); } } @Override public CharsRef getNoOutput() { return NO_OUTPUT; } @Override public String outputToString(CharsRef output) { return output.toString(); } private static final long BASE_NUM_BYTES = RamUsageEstimator.shallowSizeOf(NO_OUTPUT); @Override public long ramBytesUsed(CharsRef output) { return BASE_NUM_BYTES + RamUsageEstimator.sizeOf(output.chars); } }