117 lines
3.3 KiB
Java
117 lines
3.3 KiB
Java
// newio/MappedIO.java
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import java.nio.*;
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import java.nio.channels.*;
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import java.io.*;
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public class MappedIO {
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private static int numOfInts = 4000000;
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private static int numOfUbuffInts = 200000;
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private abstract static class Tester {
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private String name;
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public Tester(String name) { this.name = name; }
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public void runTest() {
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System.out.print(name + ": ");
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try {
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long start = System.nanoTime();
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test();
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double duration = System.nanoTime() - start;
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System.out.format("%.2f\n", duration/1.0e9);
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} catch(IOException e) {
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throw new RuntimeException(e);
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}
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}
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public abstract void test() throws IOException;
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}
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private static Tester[] tests = {
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new Tester("Stream Write") {
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@Override
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public void test() throws IOException {
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try(DataOutputStream dos = new DataOutputStream(
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new BufferedOutputStream(
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new FileOutputStream(
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new File("temp.tmp"))))) {
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for(int i = 0; i < numOfInts; i++)
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dos.writeInt(i);
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}
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}
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},
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new Tester("Mapped Write") {
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@Override
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public void test() throws IOException {
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try(FileChannel fc =
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new RandomAccessFile("temp.tmp", "rw")
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.getChannel()) {
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IntBuffer ib = fc.map(
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FileChannel.MapMode.READ_WRITE, 0, fc.size())
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.asIntBuffer();
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for(int i = 0; i < numOfInts; i++)
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ib.put(i);
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}
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}
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},
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new Tester("Stream Read") {
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@Override
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public void test() throws IOException {
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try(DataInputStream dis = new DataInputStream(
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new BufferedInputStream(
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new FileInputStream("temp.tmp")))) {
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for(int i = 0; i < numOfInts; i++)
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dis.readInt();
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}
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}
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},
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new Tester("Mapped Read") {
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@Override
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public void test() throws IOException {
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try(FileChannel fc = new FileInputStream(
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new File("temp.tmp")).getChannel()) {
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IntBuffer ib = fc.map(
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FileChannel.MapMode.READ_ONLY, 0, fc.size())
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.asIntBuffer();
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while(ib.hasRemaining())
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ib.get();
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}
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}
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},
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new Tester("Stream Read/Write") {
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@Override
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public void test() throws IOException {
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try(RandomAccessFile raf = new RandomAccessFile(
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new File("temp.tmp"), "rw")) {
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raf.writeInt(1);
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for(int i = 0; i < numOfUbuffInts; i++) {
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raf.seek(raf.length() - 4);
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raf.writeInt(raf.readInt());
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}
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}
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}
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},
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new Tester("Mapped Read/Write") {
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@Override
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public void test() throws IOException {
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try(FileChannel fc = new RandomAccessFile(
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new File("temp.tmp"), "rw").getChannel()) {
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IntBuffer ib = fc.map(
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FileChannel.MapMode.READ_WRITE, 0, fc.size())
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.asIntBuffer();
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ib.put(0);
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for(int i = 1; i < numOfUbuffInts; i++)
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ib.put(ib.get(i - 1));
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}
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}
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}
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};
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public static void main(String[] args) {
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for(Tester test : tests)
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test.runTest();
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}
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}
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/* Output:
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Stream Write: 0.45
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Mapped Write: 0.04
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Stream Read: 0.42
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Mapped Read: 0.03
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Stream Read/Write: 3.43
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Mapped Read/Write: 0.00
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*/
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