import java.io.*;
import java.util.*;

public class Test {

	public static void main(String[] args) {

		try {
			//test string
			String str = args[0];
			String rep = args[1];
			String inFile = args[2];
			String outFile = args[3];
			
			System.out.println( "Test String: " + str );
			byte[] pattern = str.getBytes();
			System.out.println( "Replace with: " + rep );
			byte[] replace = rep.getBytes();

			//read file into array
			BufferedInputStream input = new BufferedInputStream(new FileInputStream(inFile));
			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
			int b = input.read();
			while (b != -1) {
				buffer.write(b);
				b = input.read();
			}
			byte [] file = buffer.toByteArray();
			buffer.reset();
			System.out.println(inFile + " size: " + file.length + " bytes.");

			// search thru file & replace
			byte [] test = new byte[pattern.length];
			for (int i=0; i < file.length; i++) {
				if (file[i] == pattern[0] && (i + pattern.length) <= file.length ) {
					System.arraycopy( file, i, test, 0, pattern.length);
					if (Arrays.equals( pattern, test )) {
						System.out.println("Match at: " + i);
						buffer.write(replace, 0, replace.length);
						i += (pattern.length - 1);
						continue;
					}
				}
				buffer.write(file[i]);
			}

			byte [] newFile = buffer.toByteArray();
			buffer.close();
			// write out new file if changed
			if (! Arrays.equals(file, newFile) && ! outFile.equals("null")) {
				BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(outFile));
				output.write(newFile, 0, newFile.length);
				output.close();
				System.out.println("Wrote new file: " + outFile);
			} else {
				System.out.println("File not written");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static void print(byte [] pattern) {
		for (int i=0; i < pattern.length; i++) {
			System.out.print( pattern[i] + " ");
		}
		System.out.println();
		System.out.println();
	}
}