/*
* 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.RamUsageEstimator;
/**
* An FST {@link Outputs} implementation where each output
* is one or two non-negative long values. If it's a
* single output, Long is returned; else, TwoLongs. Order
* is preserved in the TwoLongs case, ie .first is the first
* input/output added to Builder, and .second is the
* second. You cannot store 0 output with this (that's
* reserved to mean "no output")!
*
* <p>NOTE: the only way to create a TwoLongs output is to
* add the same input to the FST twice in a row. This is
* how the FST maps a single input to two outputs (e.g. you
* cannot pass a TwoLongs to {@link Builder#add}. If you
* need more than two then use {@link ListOfOutputs}, but if
* you only have at most 2 then this implementation will
* require fewer bytes as it steals one bit from each long
* value.
*
* <p>NOTE: the resulting FST is not guaranteed to be minimal!
* See {@link Builder}.
*
* @lucene.experimental
*/
public final class UpToTwoPositiveIntOutputs extends Outputs<Object> {
/** Holds two long outputs. */
public final static class TwoLongs {
public final long first;
public final long second;
public TwoLongs(long first, long second) {
this.first = first;
this.second = second;
assert first >= 0;
assert second >= 0;
}
@Override
public String toString() {
return "TwoLongs:" + first + "," + second;
}
@Override
public boolean equals(Object _other) {
if (_other instanceof TwoLongs) {
final TwoLongs other = (TwoLongs) _other;
return first == other.first && second == other.second;
} else {
return false;
}
}
@Override
public int hashCode() {
return (int) ((first^(first>>>32)) ^ (second^(second>>32)));
}
}
private final static Long NO_OUTPUT = new Long(0);
private final boolean doShare;
private final static UpToTwoPositiveIntOutputs singletonShare = new UpToTwoPositiveIntOutputs(true);
private final static UpToTwoPositiveIntOutputs singletonNoShare = new UpToTwoPositiveIntOutputs(false);
private UpToTwoPositiveIntOutputs(boolean doShare) {
this.doShare = doShare;
}
public static UpToTwoPositiveIntOutputs getSingleton(boolean doShare) {
return doShare ? singletonShare : singletonNoShare;
}
public Long get(long v) {
if (v == 0) {
return NO_OUTPUT;
} else {
return Long.valueOf(v);
}
}
public TwoLongs get(long first, long second) {
return new TwoLongs(first, second);
}
@Override
public Long common(Object _output1, Object _output2) {
assert valid(_output1, false);
assert valid(_output2, false);
final Long output1 = (Long) _output1;
final Long output2 = (Long) _output2;
if (output1 == NO_OUTPUT || output2 == NO_OUTPUT) {
return NO_OUTPUT;
} else if (doShare) {
assert output1 > 0;
assert output2 > 0;
return Math.min(output1, output2);
} else if (output1.equals(output2)) {
return output1;
} else {
return NO_OUTPUT;
}
}
@Override
public Long subtract(Object _output, Object _inc) {
assert valid(_output, false);
assert valid(_inc, false);
final Long output = (Long) _output;
final Long inc = (Long) _inc;
assert output >= inc;
if (inc == NO_OUTPUT) {
return output;
} else if (output.equals(inc)) {
return NO_OUTPUT;
} else {
return output - inc;
}
}
@Override
public Object add(Object _prefix, Object _output) {
assert valid(_prefix, false);
assert valid(_output, true);
final Long prefix = (Long) _prefix;
if (_output instanceof Long) {
final Long output = (Long) _output;
if (prefix == NO_OUTPUT) {
return output;
} else if (output == NO_OUTPUT) {
return prefix;
} else {
return prefix + output;
}
} else {
final TwoLongs output = (TwoLongs) _output;
final long v = prefix;
return new TwoLongs(output.first + v, output.second + v);
}
}
@Override
public void write(Object _output, DataOutput out) throws IOException {
assert valid(_output, true);
if (_output instanceof Long) {
final Long output = (Long) _output;
out.writeVLong(output<<1);
} else {
final TwoLongs output = (TwoLongs) _output;
out.writeVLong((output.first<<1) | 1);
out.writeVLong(output.second);
}
}
@Override
public Object read(DataInput in) throws IOException {
final long code = in.readVLong();
if ((code & 1) == 0) {
// single long
final long v = code >>> 1;
if (v == 0) {
return NO_OUTPUT;
} else {
return Long.valueOf(v);
}
} else {
// two longs
final long first = code >>> 1;
final long second = in.readVLong();
return new TwoLongs(first, second);
}
}
private boolean valid(Long o) {
assert o != null;
assert o instanceof Long;
assert o == NO_OUTPUT || o > 0;
return true;
}
// Used only by assert
private boolean valid(Object _o, boolean allowDouble) {
if (!allowDouble) {
assert _o instanceof Long;
return valid((Long) _o);
} else if (_o instanceof TwoLongs) {
return true;
} else {
return valid((Long) _o);
}
}
@Override
public Object getNoOutput() {
return NO_OUTPUT;
}
@Override
public String outputToString(Object output) {
return output.toString();
}
@Override
public Object merge(Object first, Object second) {
assert valid(first, false);
assert valid(second, false);
return new TwoLongs((Long) first, (Long) second);
}
private static final long TWO_LONGS_NUM_BYTES = RamUsageEstimator.shallowSizeOf(new TwoLongs(0, 0));
@Override
public long ramBytesUsed(Object o) {
if (o instanceof Long) {
return RamUsageEstimator.sizeOf((Long) o);
} else {
assert o instanceof TwoLongs;
return TWO_LONGS_NUM_BYTES;
}
}
}