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oj! Algorithms - ojAlgo - is Open Source Java code that has to do with mathematics, linear algebra and optimisation.
/*
* Copyright 1997-2024 Optimatika
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.ojalgo.netio;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.io.UncheckedIOException;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.util.List;
import java.util.function.IntSupplier;
import org.ojalgo.OjAlgoUtils;
import org.ojalgo.concurrent.Parallelism;
import org.ojalgo.function.special.PowerOf2;
/**
* Divides a large file in segments and then reads those (in parallel) using memory mapped files (memory
* mapped file segments). Basic usage:
*
* - Call {@link #newBuilder(File)} to get a {@link Builder} or {@link #of(File)} to get a
* {@link SegmentedFile} directly with the default settings.
*
- Then for each of the segments obtained from {@link SegmentedFile#segments()}: Call
* {@link SegmentedFile#newTextLineReader(Segment)} and using that read all the lines.
*
* Multiple threads can be used to read the segments in parallel. Each thread just works on one segment at a
* time, and there's a new {@link TextLineReader} for each segment.
*/
public class SegmentedFile implements AutoCloseable {
public static final class Builder {
private static final long k = 1024L;
private long myBytesPerSegment = Math.min(PowerOf2.MAX_INT, OjAlgoUtils.ENVIRONMENT.cache);
private int myDelimiter = ASCII.LF;
private final File myFile;
private int myParallelism = Parallelism.CORES.getAsInt();
Builder(final File file) {
super();
myFile = file;
}
public SegmentedFile build() {
try {
RandomAccessFile raf = new RandomAccessFile(myFile, "r");
long nbBytesInFile = raf.length();
int nbSegments = 1;
long nbBytesPerSegment = nbBytesInFile;
while (nbBytesPerSegment > myBytesPerSegment) {
if (nbSegments == 1) {
nbSegments = myParallelism;
} else {
nbSegments += myParallelism;
}
nbBytesPerSegment = nbBytesInFile / nbSegments;
}
Segment[] segments = new Segment[nbSegments];
long start = 0L;
long end = 0L;
for (int s = 1; s <= nbSegments; s++) {
start = end;
if (s == nbSegments) {
end = nbBytesInFile;
} else {
end = Math.min(s * nbBytesPerSegment, nbBytesInFile);
raf.seek(end);
while (end < nbBytesInFile) {
end++;
if (raf.read() == myDelimiter) {
break;
}
}
}
segments[s - 1] = new Segment(start, end - start);
}
return new SegmentedFile(raf, segments);
} catch (IOException cause) {
throw new RuntimeException(cause);
}
}
/**
* The delimiter is used to determine where to split the file into segments. The default value is '\n'
* (newline).
*/
public Builder delimiter(final byte delimiter) {
myDelimiter = delimiter;
return this;
}
/**
* @see #parallelism(IntSupplier)
*/
public Builder parallelism(final int parallelism) {
myParallelism = parallelism;
return this;
}
/**
* The expected number of threads that will be used to process the file. The number of segments will a
* multiple of this number. The default value is the number of CPU cores.
*/
public Builder parallelism(final IntSupplier parallelism) {
return this.parallelism(parallelism.getAsInt());
}
/**
* The target (max) size (bytes) of each segment. The actual size will be less than or equal to this
* value. The last segment will be smaller than or equal to the other segments.
*/
public Builder segmentBytes(final long bytesPerSegment) {
myBytesPerSegment = bytesPerSegment;
return this;
}
/**
* @see #segmentBytes(long)
*/
public Builder segmentKiloBytes(final long kiloBytesPerSegment) {
return this.segmentBytes(k * kiloBytesPerSegment);
}
/**
* @see #segmentBytes(long)
*/
public Builder segmentMegaBytes(final long megaBytesPerSegment) {
return this.segmentKiloBytes(k * megaBytesPerSegment);
}
}
public static final class Segment implements Comparable {
public final long offset;
public final long size;
Segment(final long offset, final long size) {
this.offset = offset;
this.size = size;
}
@Override
public int compareTo(final Segment ref) {
return Long.compare(offset, ref.offset);
}
@Override
public boolean equals(final Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof Segment)) {
return false;
}
Segment other = (Segment) obj;
if (offset != other.offset || size != other.size) {
return false;
}
return true;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (int) (offset ^ offset >>> 32);
result = prime * result + (int) (size ^ size >>> 32);
return result;
}
public long limit() {
return offset + size;
}
@Override
public String toString() {
return "[" + offset + ", " + this.limit() + ")";
}
}
public static SegmentedFile.Builder newBuilder(final File file) {
return new Builder(file);
}
public static SegmentedFile of(final File file) {
return SegmentedFile.newBuilder(file).build();
}
private final FileChannel myFileChannel;
private final RandomAccessFile myRandomAccessFile;
private final Segment[] mySegments;
SegmentedFile(final RandomAccessFile file, final Segment[] segments) {
super();
myRandomAccessFile = file;
mySegments = segments;
myFileChannel = myRandomAccessFile.getChannel();
}
@Override
public void close() {
try {
myRandomAccessFile.close();
} catch (IOException cause) {
throw new UncheckedIOException(cause);
}
}
/**
* Call this once for each file segment, and use the returned {@link TextLineReader} to read the file
* segment. The {@link TextLineReader} is not thread safe, and should only be used by a single thread.
*
* The segment is a range of bytes in the file. The {@link TextLineReader} will read the bytes in the
* range [offset, offset + size). The segments are obtained from {@link #segments()}. The segments are
* sorted in ascending order by offset.
*/
public TextLineReader newTextLineReader(final Segment segment) {
try {
return new TextLineReader(new ByteBufferBackedInputStream(myFileChannel.map(MapMode.READ_ONLY, segment.offset, segment.size)));
} catch (IOException cause) {
throw new RuntimeException(cause);
}
}
public List segments() {
return List.of(mySegments);
}
}