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//: io/MappedIO.java

package io; /* Added by Eclipse.py */

import java.nio.*;

import java.nio.channels.*;

import java.io.*;

public class MappedIO {

private static int numOfInts = 4000000;

private static int numOfUbuffInts = 200000;

private abstract static class Tester {

private String name;

public Tester(String name) { this.name = name; }

public void runTest() {

System.out.print(name + ": ");

try {

long start = System.nanoTime();

test();

double duration = System.nanoTime() - start;

System.out.format("%.2f\n", duration/1.0e9);

} catch(IOException e) {

throw new RuntimeException(e);

}

}

public abstract void test() throws IOException;

}

private static Tester[] tests = {

new Tester("Stream Write") {

public void test() throws IOException {

DataOutputStream dos = new DataOutputStream(

new BufferedOutputStream(

new FileOutputStream(new File("temp.tmp"))));

for(int i = 0; i < numOfInts; i++)

dos.writeInt(i);

dos.close();

}

},

new Tester("Mapped Write") {

public void test() throws IOException {

FileChannel fc =

new RandomAccessFile("temp.tmp", "rw")

.getChannel();

IntBuffer ib = fc.map(

FileChannel.MapMode.READ_WRITE, 0, fc.size())

.asIntBuffer();

for(int i = 0; i < numOfInts; i++)

ib.put(i);

fc.close();

}

},

new Tester("Stream Read") {

public void test() throws IOException {

DataInputStream dis = new DataInputStream(

new BufferedInputStream(

new FileInputStream("temp.tmp")));

for(int i = 0; i < numOfInts; i++)

dis.readInt();

dis.close();

}

},

new Tester("Mapped Read") {

public void test() throws IOException {

FileChannel fc = new FileInputStream(

new File("temp.tmp")).getChannel();

IntBuffer ib = fc.map(

FileChannel.MapMode.READ_ONLY, 0, fc.size())

.asIntBuffer();

while(ib.hasRemaining())

ib.get();

fc.close();

}

},

new Tester("Stream Read/Write") {

public void test() throws IOException {

RandomAccessFile raf = new RandomAccessFile(

new File("temp.tmp"), "rw");

raf.writeInt(1);

for(int i = 0; i < numOfUbuffInts; i++) {

raf.seek(raf.length() - 4);

raf.writeInt(raf.readInt());

}

raf.close();

}

},

new Tester("Mapped Read/Write") {

public void test() throws IOException {

FileChannel fc = new RandomAccessFile(

new File("temp.tmp"), "rw").getChannel();

IntBuffer ib = fc.map(

FileChannel.MapMode.READ_WRITE, 0, fc.size())

.asIntBuffer();

ib.put(0);

for(int i = 1; i < numOfUbuffInts; i++)

ib.put(ib.get(i - 1));

fc.close();

}

}

};

public static void main(String[] args) {

for(Tester test : tests)

test.runTest();

}

} /* Output: (90% match)

Stream Write: 0.56

Mapped Write: 0.12

Stream Read: 0.80

Mapped Read: 0.07

Stream Read/Write: 5.32

Mapped Read/Write: 0.02

*///:~