io.virtdata.functional.RandomFileExtractToString Maven / Gradle / Ivy
/*
*
* Copyright 2015 Jonathan Shook
*
* 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.
*
*/
package io.virtdata.functional;
import io.virtdata.util.ResourceFinder;
import org.apache.commons.math3.distribution.IntegerDistribution;
import org.apache.commons.math3.distribution.UniformIntegerDistribution;
import org.apache.commons.math3.random.MersenneTwister;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.CharBuffer;
import java.util.function.LongFunction;
public class RandomFileExtractToString implements LongFunction {
private final static Logger logger = LoggerFactory.getLogger(RandomFileExtractToString.class);
private static CharBuffer fileDataImage =null;
private int minsize, maxsize;
private final MersenneTwister rng;
private final IntegerDistribution sizeDistribution;
private final IntegerDistribution positionDistribution;
private final String fileName;
public RandomFileExtractToString(String fileName, int minsize, int maxsize) {
this(fileName, minsize,maxsize,System.nanoTime());
}
public RandomFileExtractToString(String fileName, int minsize, int maxsize, long seed) {
this.fileName = fileName;
this.minsize = minsize;
this.maxsize = maxsize;
loadData();
this.rng = new MersenneTwister(seed);
this.sizeDistribution = new UniformIntegerDistribution(rng, minsize, maxsize);
this.positionDistribution = new UniformIntegerDistribution(rng, 1, fileDataImage.limit() - maxsize);
}
private void loadData() {
if (fileDataImage == null) {
synchronized (RandomFileExtractToString.class) {
if (fileDataImage == null) {
CharBuffer image= ResourceFinder.readDataFileToCharBuffer(fileName);
fileDataImage = image;
}
}
}
}
@Override
public String apply(long input) {
int offset = positionDistribution.sample();
int length = sizeDistribution.sample();
String sub = null;
try {
sub = fileDataImage.subSequence(offset, offset + length).toString();
} catch (Exception e) {
throw new RuntimeException(e);
}
return sub;
}
public String toString() {
return getClass().getSimpleName() + ":" + minsize + ":" + maxsize;
}
}