// io/AllocateDirectTest25.java
// TIJ4 Chapter IO, Exercise 25, page 970
/* Experiment with changing the ByteBuffer.allocate() statements
* in the examples in this chapter to ByteBuffer.allocateDirect().
* Demonstrate performance differences, but also notice whether
* the startup time of the programs noticeably changes.
*/

/* My solution to one of the exercises in 
* Thinking in Java 4th Edition (by Bruce Eckel).
* It compiles and runs correctly using JDK 1.6.0
* @author Greg Gordon
* @author www.greggordon.org
* April, 2008
*/

import java.nio.*;
import java.nio.channels.*;
import java.io.*;
import static net.mindview.util.Print.*;
import java.nio.charset.*;
import net.mindview.util.*;
import java.lang.reflect.*;
 
public class AllocateDirectTest25 {	
	// Method to copy file, replace  allocate() 
	// with allocateDirect(), and rename fileDirect:  
	public static File toDirect(File f) throws IOException {
		FileChannel fcIn = new FileInputStream(f).getChannel();	
		ByteBuffer b = ByteBuffer.allocateDirect((int)f.length());
		fcIn.read(b);
		b.flip();
		Charset cs = Charset.defaultCharset();	
		CharBuffer cb = cs.decode(b);
		String cbD1 = cb.toString().replace(
			".allocate(", ".allocateDirect(");
		String cbD = cbD1.replace(f.getName().split("\\.")[0], 
			f.getName().split("\\.")[0] + "Direct");
		CharBuffer cbNew = CharBuffer.wrap(cbD);
		String ext = (f.getName().split("\\."))[1];
		String outFile = (f.getName().split("\\."))[0] + 
			"Direct." + ext;
		FileChannel fcOut = 
			new FileOutputStream(
				new File(outFile)).getChannel();
		fcOut.write(cs.encode(cbNew));		
		// fcIn.transferTo(0, f.length(), fcOut);		
		fcIn.close();
		fcOut.close();
		return new File(outFile);
	}
	// Methods to test performance
	public static void Tester(String s) {
		try { // Uses reflection to call main methods:
			Class c = Class.forName(s);
			String name = c.getSimpleName();
			print("Testing: " + name);
			@SuppressWarnings("unchecked")
			Method m = c.getMethod("main", String[].class);
			// To test ChannelCopy.class
			// (otherwise (String)null OK for second argument):
			String[] sa = new String[]{"ChannelCopy.java", "Test.txt"};
			long startRun = System.nanoTime(); 
			m.invoke(c.newInstance(), (Object)sa);
			long duration = System.nanoTime() - startRun;
			print("\nTime to run " + name + " = " 
				+ duration + " nanoseconds");				
		} catch(Exception e) {
			e.printStackTrace(System.err);
		}
	}
	public static long allocationTime(int i) { 
		long start = System.nanoTime();
		ByteBuffer bb = ByteBuffer.allocate(i);
		return System.nanoTime() - start;
	}	
	public static long directAllocationTime(int i) { 
		long start = System.nanoTime();
		ByteBuffer bb = ByteBuffer.allocateDirect(i);
		return System.nanoTime() - start;
	}
	
	public static void main(final String[] args) throws IOException {
		// allocation time related to statup time:
		print("Time to allocate 1024 bytes = " 
			+ allocationTime(1024) + " nanoseconds");
		print("Time to allocateDirect 1024 bytes = " 
			+ directAllocationTime(1024) + " nanoseconds");
		print("Time to allocate 48 bytes = " 
			+ allocationTime(48) + " nanoseconds");
		print("Time to allocateDirect 48 bytes = " 
			+ directAllocationTime(48) + " nanoseconds");
		print("Time to allocate 1 byte = " 
			+ allocationTime(1) + " nanoseconds");
		print("Time to allocateDirect 1 byte = " 
			+ directAllocationTime(1) + " nanoseconds");
		Tester("GetChannel");
		toDirect(new File("GetChannel.java"));
		// after compiling GetChannelDirect:
		Tester("GetChannelDirect");
		Tester("BufferToText");
		toDirect(new File("BufferToText.java"));
		// after compiling BufferToText.java:
		Tester("BufferToTextDirect");
		Tester("ChannelCopy");
		toDirect(new File("ChannelCopy.java"));
		// after compiling ChannelCopyDirect.java:
		Tester("ChannelCopyDirect");
		Tester("GetData");
		toDirect(new File("GetData.java"));
		// after compiling GetDataDirect.java:
		Tester("GetDataDirect");
		Tester("IntBufferDemo");
		toDirect(new File("IntBufferDemo.java"));
		// after compiling IntBufferDemoDirect.java:
		Tester("IntBufferDemoDirect");
		Tester("UsingBuffers");
		toDirect(new File("UsingBuffers.java"));
		// after compiling UsingBuffersDirect.java:
		Tester("UsingBuffersDirect");
	}
}