// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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 com.twitter.common.text.token;
import java.util.Iterator;
import java.util.List;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import org.apache.lucene.util.Attribute;
/**
* Aggregates the outputs of multiple {@code TokenStreams} into a single {@code TokenStream}.
*/
public class TokenStreamAggregator extends TokenStream {
private final List<TokenStream> aggregatedStreams;
protected TokenStreamAggregator(TokenStream... streams) {
aggregatedStreams = ImmutableList.copyOf(streams);
// register all attributes of every stream
for (TokenStream stream : streams) {
Iterator<Class<? extends Attribute>> it = stream.getAttributeClassesIterator();
while (it.hasNext()) {
addAttribute(it.next());
}
}
}
/**
* Creates a {@code TokenStream} that aggregates the outputs of a given set of
* {@code TokenStreams}.
*
* @param streams TokenStreams to aggregate
* @return an aggregated TokenStream
*/
public static final TokenStream of(TokenStream... streams) {
return new TokenStreamAggregator(streams);
}
@Override
public boolean incrementToken() {
for (TokenStream stream : aggregatedStreams) {
if (!stream.incrementToken()) {
continue;
}
restoreState(stream.captureState());
return true;
}
// No stream has more token.
return false;
}
@Override
public void reset(CharSequence input) {
Preconditions.checkNotNull(input);
for (TokenStream stream : aggregatedStreams) {
stream.reset(input);
}
}
}