/*
 * 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.BytesRef;
import org.apache.lucene.util.RamUsageEstimator;
import org.apache.lucene.util.StringHelper;

An FST Outputs implementation where each output is a sequence of bytes.
@lucene.experimental
/** * An FST {@link Outputs} implementation where each output * is a sequence of bytes. * * @lucene.experimental */
public final class ByteSequenceOutputs extends Outputs<BytesRef> { private final static BytesRef NO_OUTPUT = new BytesRef(); private final static ByteSequenceOutputs singleton = new ByteSequenceOutputs(); private ByteSequenceOutputs() { } public static ByteSequenceOutputs getSingleton() { return singleton; } @Override public BytesRef common(BytesRef output1, BytesRef 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.bytes[pos1] != output2.bytes[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 BytesRef(output1.bytes, output1.offset, pos1-output1.offset); } } @Override public BytesRef subtract(BytesRef output, BytesRef inc) { assert output != null; assert inc != null; if (inc == NO_OUTPUT) { // no prefix removed return output; } else { assert StringHelper.startsWith(output, inc); 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 BytesRef(output.bytes, output.offset + inc.length, output.length-inc.length); } } } @Override public BytesRef add(BytesRef prefix, BytesRef 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; BytesRef result = new BytesRef(prefix.length + output.length); System.arraycopy(prefix.bytes, prefix.offset, result.bytes, 0, prefix.length); System.arraycopy(output.bytes, output.offset, result.bytes, prefix.length, output.length); result.length = prefix.length + output.length; return result; } } @Override public void write(BytesRef prefix, DataOutput out) throws IOException { assert prefix != null; out.writeVInt(prefix.length); out.writeBytes(prefix.bytes, prefix.offset, prefix.length); } @Override public BytesRef read(DataInput in) throws IOException { final int len = in.readVInt(); if (len == 0) { return NO_OUTPUT; } else { final BytesRef output = new BytesRef(len); in.readBytes(output.bytes, 0, len); output.length = len; return output; } } @Override public void skipOutput(DataInput in) throws IOException { final int len = in.readVInt(); if (len != 0) { in.skipBytes(len); } } @Override public BytesRef getNoOutput() { return NO_OUTPUT; } @Override public String outputToString(BytesRef output) { return output.toString(); } private static final long BASE_NUM_BYTES = RamUsageEstimator.shallowSizeOf(NO_OUTPUT); @Override public long ramBytesUsed(BytesRef output) { return BASE_NUM_BYTES + RamUsageEstimator.sizeOf(output.bytes); } @Override public String toString() { return "ByteSequenceOutputs"; } }