package ch.dietpizza.iometrics;

import static java.lang.String.format;
import static java.lang.System.currentTimeMillis;
import static java.lang.System.out;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

public class OptimalBufferSizeSquentialReader {

	public static void main(String[] args) throws IOException, InterruptedException {
		System.err.println("Staring...");
		//warm up
		Thread.sleep(250); 
		goJavaIoBufferedInputStream(10, 128);
		Thread.sleep(250); 
		goJavaIoBufferedInputStream(11, 256);
		Thread.sleep(250); 
		
		//explicate buffer size
		for (int loop = -1; loop < 16; loop++) {
 			for (int payloadSize = 1; payloadSize <= 262144; payloadSize *= 2) {
 				Thread.sleep(100); //System.err is unbuffered
 				goJavaIoBufferedInputStream(loop, payloadSize);
 			}
		}
		
		Thread.sleep(100); //System.err is unbuffered
		System.err.println("Done!");
	}	
	
	private static void goJavaIoBufferedInputStream(int loop, int payloadSize) throws IOException {
		long start = currentTimeMillis();
		int buffSize =  (int) Math.pow (2, loop);
		File file= new File(format("%s-%d-%d.test", Common.TEST_FILE.replace("Movies", "Movies/test"), loop == -1 ? 1 : buffSize , payloadSize));
		
		InputStream is = loop > 0 ? new BufferedInputStream(new FileInputStream(file), buffSize) : new BufferedInputStream(new FileInputStream(file));
		long result = 0;
		byte[] payload = new byte[payloadSize];
		
		int readIn = is.read(payload);
		long loops = 0;
		while (readIn >= 0)  {
	   	    for (int i = 0; i < payload.length; i++) {
				result += payload[i] & 0xFF;
				payload[i] = 0;
				loops++;
			}
			readIn = is.read(payload);
		}
		
		float time = (currentTimeMillis() - start) / 1000F; //to seconds	
		float fileSize = (float)(file.length())    / 1024F; //to kilobytes
		out.println(format("%d, %d, %f", buffSize, payloadSize, (fileSize / time)));
	}	
}