import java.io.*;
import java.math.BigInteger;

public class BinaryPatcher {
	private String content;

	private final String filename;
	private final String searchPattern;
	private final String replacePattern;

	public BinaryPatcher(String filename, String searchPattern,
			String replacePattern) throws IOException {

		this.filename = filename;
		this.searchPattern = convertHexStringToBinaryString(searchPattern);
		this.replacePattern = convertHexStringToBinaryString(replacePattern);

		initializeContent();
	}

	public boolean isPatchable() {
		return getContent().contains(searchPattern);
	}

	public void patch() throws IOException {
		if (!isPatchable()) {
			throw new IOException("Search pattern not found");
		}

		String originalContent = getContent();
		String patchedContent = originalContent.replace(searchPattern,
				replacePattern);

		saveStringToFile(patchedContent, filename);
	}

	public void createBackup(String filename) throws IOException {
		saveStringToFile(getContent(), filename);
	}

	private static String convertHexStringToBinaryString(String theHexString) {
		byte[] byteSequence = new BigInteger(theHexString, 16).toByteArray();
		return new String(byteSequence);
	}

	private void initializeContent() throws IOException {
		byte[] buffer = new byte[(int) new File(filename).length()];
		FileInputStream in = new FileInputStream(filename);
		in.read(buffer);
		in.close();
		content = new String(buffer);
	}

	private void saveStringToFile(String content, String filename)
			throws IOException {
		FileOutputStream out = new FileOutputStream(filename);
		out.write(content.getBytes());
		out.close();
	}

	private String getContent() {
		return content;
	}
}