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Protempa Framework is the core of Protempa.
/*
* #%L
* Protempa Framework
* %%
* Copyright (C) 2012 - 2013 Emory University
* %%
* Licensed 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.
* #L%
*/
package org.protempa;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import org.protempa.proposition.Proposition;
/**
* Provides the same functionality as {@link DataStreamer} except as an
* iterator. While {@link DataStreamer} implements pushing data from a data
* source to the caller, this iterator supports pulling data from the data
* source.
* @author Andrew Post
*/
final class DataStreamerIterator implements AutoCloseable {
private final List> itrs;
private final List> currentElt;
private boolean hasNext;
private DataStreamingEvent result;
private boolean hasNextComputed;
private int i = 0;
private DataStreamingEvent currentMin;
private String nextKeyId;
/**
* Constructs an iterator with a list of iterators containing data from the
* data source.
*
* @param itrs the iterators.
* @throws SQLException if an error occurred querying the underlying
* database during iteration.
*/
DataStreamerIterator(List> itrs)
throws DataSourceReadException {
assert itrs != null : "itrs cannot be null";
this.itrs = itrs;
this.currentElt = new ArrayList<>(itrs.size());
int itrsSize = itrs.size();
for (int j = 0; j < itrsSize; j++) {
this.currentElt.add(null);
}
/*
* Stores the most recent element retrieved from each iterator.
*/
/*
* Stores the most recent element retrieved from each iterator.
*/
for (int j = 0; j < itrsSize; j++) {
advance(j);
}
/*
* If the iterators have no elements, cut to the chase and arrange for
* {@link #hasNext()} to return immediately.
*/
/*
* If the iterators have no elements, cut to the chase and arrange for
* {@link #hasNext()} to return immediately.
*/
for (DataStreamingEvent event : this.currentElt) {
if (event != null) {
this.hasNext = true;
break;
}
}
}
String getNextKeyId() {
return this.nextKeyId;
}
/**
* We loop through the iterators passed into the constructor and return
* whether the the next item in at least one iterator is for the right
* keyId.
*
* @return
* true or
* false.
*/
boolean hasNext() throws DataSourceReadException {
if (!hasNextComputed) {
boolean stayInLoop;
do {
stayInLoop = false;
/*
* Prior to reading the first iterator, we loop through all of
* the iterators to determine the minimum keyId. The minimum
* keyId, stored in currentMin, is used for data retrieval. The
* value of currentMin will be null if there is no data to
* retrieve.
*/
if (i == 0) {
this.currentMin = null;
for (DataStreamingEvent elt : this.currentElt) {
currentMin = min(elt);
}
}
/*
* If there is no data to retrieve, we'll return false. If there
* is data to retrieve, we'll loop through the iterators and
* pull data for the current keyId, which is the keyId field of
* currentMin. If there's no data for the current keyId, this
* should loop through all of the iterators until their ends,
* and set hasNext to false.
*/
if (currentMin == null) {
this.hasNext = false;
} else {
int n = this.currentElt.size();
for (; i < n; i++) {
DataStreamingEvent elt = this.currentElt.get(i);
if (elt != null && elt.getKeyId().equals(
this.currentMin != null
? this.currentMin.getKeyId() : null)) {
this.result = elt;
this.nextKeyId = elt.getKeyId();
advance(i);
i++;
break;
}
}
if (this.i == n && this.result == null) {
this.i = 0;
stayInLoop = true;
}
}
} while (this.hasNext && stayInLoop);
this.hasNextComputed = true;
}
return hasNext;
}
DataStreamingEvent next() {
assert this.result != null : "result cannot be null";
this.hasNextComputed = false;
DataStreamingEvent r = this.result;
this.result = null;
this.nextKeyId = null;
return r;
}
private void advance(int j)
throws DataSourceReadException {
DataStreamingEventIterator itr = this.itrs.get(j);
if (itr.hasNext()) {
DataStreamingEvent next = itr.next();
this.currentElt.set(j, next);
} else {
this.currentElt.set(j, null);
}
}
private DataStreamingEvent min(DataStreamingEvent elt2) {
DataStreamingEvent elt1 = this.currentMin;
if (elt1 == null) {
return elt2;
} else if (elt2 == null) {
return elt1;
} else {
return elt1.getKeyId().compareTo(elt2.getKeyId()) < 0 ? elt1 : elt2;
}
}
public void close() {
}
}