package org.apache.lucene.util.fst;
/*
* 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.
*/
import java.io.IOException;
import org.apache.lucene.store.DataInput;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.util.CharsRef;
/**
* 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();
}
}