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139 lines (138 loc) · 3.84 KB
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// newio/MappedIO.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {ExcludeFromGradle} Runs too long under WSL2
import java.util.*;
import java.nio.*;
import java.nio.channels.*;
import java.io.*;
public class MappedIO {
private static int numOfInts = 4_000_000;
private static int numOfUbuffInts = 100_000;
private abstract static class Tester {
private String name;
Tester(String name) {
this.name = name;
}
public void runTest() {
System.out.print(name + ": ");
long start = System.nanoTime();
test();
double duration = System.nanoTime() - start;
System.out.format("%.3f%n", duration/1.0e9);
}
public abstract void test();
}
private static Tester[] tests = {
new Tester("Stream Write") {
@Override public void test() {
try(
DataOutputStream dos =
new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream(
new File("temp.tmp"))))
) {
for(int i = 0; i < numOfInts; i++)
dos.writeInt(i);
} catch(IOException e) {
throw new RuntimeException(e);
}
}
},
new Tester("Mapped Write") {
@Override public void test() {
try(
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);
} catch(IOException e) {
throw new RuntimeException(e);
}
}
},
new Tester("Stream Read") {
@Override public void test() {
try(
DataInputStream dis =
new DataInputStream(
new BufferedInputStream(
new FileInputStream("temp.tmp")))
) {
for(int i = 0; i < numOfInts; i++)
dis.readInt();
} catch(IOException e) {
throw new RuntimeException(e);
}
}
},
new Tester("Mapped Read") {
@Override public void test() {
try(
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();
} catch(IOException e) {
throw new RuntimeException(e);
}
}
},
new Tester("Stream Read/Write") {
@Override public void test() {
try(
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());
}
} catch(IOException e) {
throw new RuntimeException(e);
}
}
},
new Tester("Mapped Read/Write") {
@Override public void test() {
try(
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));
} catch(IOException e) {
throw new RuntimeException(e);
}
}
}
};
public static void main(String[] args) {
Arrays.stream(tests).forEach(Tester::runTest);
}
}
/* Output:
Stream Write: 0.615
Mapped Write: 0.050
Stream Read: 0.577
Mapped Read: 0.015
Stream Read/Write: 4.069
Mapped Read/Write: 0.013
*/