org.apache.lucene.util.fst.Outputs Maven / Gradle / Ivy
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.Accountable;
/**
* Represents the outputs for an FST, providing the basic
* algebra required for building and traversing the FST.
*
* Note that any operation that returns NO_OUTPUT must
* return the same singleton object from {@link
* #getNoOutput}.
*
* @lucene.experimental
*/
public abstract class Outputs {
// TODO: maybe change this API to allow for re-use of the
// output instances -- this is an insane amount of garbage
// (new object per byte/char/int) if eg used during
// analysis
/** Eg common("foobar", "food") -> "foo" */
public abstract T common(T output1, T output2);
/** Eg subtract("foobar", "foo") -> "bar" */
public abstract T subtract(T output, T inc);
/** Eg add("foo", "bar") -> "foobar" */
public abstract T add(T prefix, T output);
/** Encode an output value into a {@link DataOutput}. */
public abstract void write(T output, DataOutput out) throws IOException;
/** Encode an final node output value into a {@link
* DataOutput}. By default this just calls {@link #write(Object,
* DataOutput)}. */
public void writeFinalOutput(T output, DataOutput out) throws IOException {
write(output, out);
}
/** Decode an output value previously written with {@link
* #write(Object, DataOutput)}. */
public abstract T read(DataInput in) throws IOException;
/** Skip the output; defaults to just calling {@link #read}
* and discarding the result. */
public void skipOutput(DataInput in) throws IOException {
read(in);
}
/** Decode an output value previously written with {@link
* #writeFinalOutput(Object, DataOutput)}. By default this
* just calls {@link #read(DataInput)}. */
public T readFinalOutput(DataInput in) throws IOException {
return read(in);
}
/** Skip the output previously written with {@link #writeFinalOutput};
* defaults to just calling {@link #readFinalOutput} and discarding
* the result. */
public void skipFinalOutput(DataInput in) throws IOException {
skipOutput(in);
}
/** NOTE: this output is compared with == so you must
* ensure that all methods return the single object if
* it's really no output */
public abstract T getNoOutput();
public abstract String outputToString(T output);
// TODO: maybe make valid(T output) public...? for asserts
public T merge(T first, T second) {
throw new UnsupportedOperationException();
}
/** Return memory usage for the provided output.
* @see Accountable */
public abstract long ramBytesUsed(T output);
}