/*
* 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 opennlp.maxent;
import opennlp.model.AbstractEventStream;
import opennlp.model.Event;
/**
* A object which can deliver a stream of training events assuming
* that each event is represented as a separated list containing
* all the contextual predicates, with the last item being the
* outcome. The default separator is the space " ".
* e.g.:
*
* <p> cp_1 cp_2 ... cp_n outcome
* <p> cp_1,cp_2,...,cp_n,outcome
*/
public class BasicEventStream extends AbstractEventStream {
ContextGenerator cg;
DataStream ds;
Event next;
private String separator = " ";
public BasicEventStream (DataStream ds, String sep) {
separator = sep;
cg = new BasicContextGenerator(separator);
this.ds = ds;
if (this.ds.hasNext())
next = createEvent((String)this.ds.nextToken());
}
public BasicEventStream (DataStream ds) {
this(ds, " ");
}
/**
* Returns the next Event object held in this EventStream. Each call to nextEvent advances the EventStream.
*
* @return the Event object which is next in this EventStream
*/
public Event next () {
while (next == null && this.ds.hasNext())
next = createEvent((String)this.ds.nextToken());
Event current = next;
if (this.ds.hasNext()) {
next = createEvent((String)this.ds.nextToken());
}
else {
next = null;
}
return current;
}
/**
* Test whether there are any Events remaining in this EventStream.
*
* @return true if this EventStream has more Events
*/
public boolean hasNext () {
while (next == null && ds.hasNext())
next = createEvent((String)ds.nextToken());
return next != null;
}
private Event createEvent(String obs) {
int lastSpace = obs.lastIndexOf(separator);
if (lastSpace == -1)
return null;
else
return new Event(obs.substring(lastSpace+1),
cg.getContext(obs.substring(0, lastSpace)));
}
}