tikhomirov@31: /*
tikhomirov@31:  * Copyright (c) 2010, 2011 Artem Tikhomirov 
tikhomirov@9:  */
tikhomirov@9: package com.tmate.hgkit.ll;
tikhomirov@9: 
tikhomirov@9: import java.io.IOException;
tikhomirov@9: import java.io.InputStream;
tikhomirov@9: import java.security.MessageDigest;
tikhomirov@9: import java.security.NoSuchAlgorithmException;
tikhomirov@9: 
tikhomirov@9: /**
tikhomirov@42:  * <pre>
tikhomirov@42:  * DigestHelper dh;
tikhomirov@42:  * dh.sha1(...).asHexString();
tikhomirov@42:  *  or 
tikhomirov@42:  * dh = dh.sha1(...);
tikhomirov@42:  * nodeid.equalsTo(dh.asBinary());
tikhomirov@42:  * </pre>
tikhomirov@9:  * @author artem
tikhomirov@9:  */
tikhomirov@9: public class DigestHelper {
tikhomirov@9: 	private MessageDigest sha1;
tikhomirov@42: 	private byte[] digest;
tikhomirov@9: 
tikhomirov@9: 	public DigestHelper() {
tikhomirov@9: 	}
tikhomirov@9: 	
tikhomirov@9: 	private MessageDigest getSHA1() {
tikhomirov@9: 		if (sha1 == null) {
tikhomirov@9: 			try {
tikhomirov@9: 				sha1 = MessageDigest.getInstance("SHA-1");
tikhomirov@9: 			} catch (NoSuchAlgorithmException ex) {
tikhomirov@9: 				// could hardly happen, JDK from Sun always has sha1.
tikhomirov@9: 				ex.printStackTrace(); // FIXME log error
tikhomirov@9: 			}
tikhomirov@9: 		}
tikhomirov@9: 		return sha1;
tikhomirov@9: 	}
tikhomirov@9: 
tikhomirov@41: 
tikhomirov@42: 	public DigestHelper sha1(Nodeid nodeid1, Nodeid nodeid2, byte[] data) {
tikhomirov@41: 		return sha1(nodeid1.cloneData(), nodeid2.cloneData(), data);
tikhomirov@41: 	}
tikhomirov@41: 
tikhomirov@41: 	//  sha1_digest(min(p1,p2) ++ max(p1,p2) ++ final_text)
tikhomirov@42: 	public DigestHelper sha1(byte[] nodeidParent1, byte[] nodeidParent2, byte[] data) {
tikhomirov@9: 		MessageDigest alg = getSHA1();
tikhomirov@41: 		if ((nodeidParent1[0] & 0x00FF) < (nodeidParent2[0] & 0x00FF)) { 
tikhomirov@41: 			alg.update(nodeidParent1);
tikhomirov@41: 			alg.update(nodeidParent2);
tikhomirov@41: 		} else {
tikhomirov@41: 			alg.update(nodeidParent2);
tikhomirov@41: 			alg.update(nodeidParent1);
tikhomirov@41: 		}
tikhomirov@42: 		digest = alg.digest(data);
tikhomirov@9: 		assert digest.length == 20;
tikhomirov@42: 		return this;
tikhomirov@42: 	}
tikhomirov@42: 	
tikhomirov@42: 	public String asHexString() {
tikhomirov@42: 		if (digest == null) {
tikhomirov@42: 			throw new IllegalStateException("Shall init with sha1() call first");
tikhomirov@42: 		}
tikhomirov@42: 		return toHexString(digest, 0, digest.length);
tikhomirov@42: 	}
tikhomirov@42: 	
tikhomirov@42: 	// by reference, be careful not to modify (or #clone() if needed)
tikhomirov@42: 	public byte[] asBinary() {
tikhomirov@42: 		if (digest == null) {
tikhomirov@42: 			throw new IllegalStateException("Shall init with sha1() call first");
tikhomirov@42: 		}
tikhomirov@42: 		return digest; 
tikhomirov@9: 	}
tikhomirov@9: 
tikhomirov@41: 	// XXX perhaps, digest functions should throw an exception, as it's caller responsibility to deal with eof, etc
tikhomirov@42: 	public DigestHelper sha1(InputStream is /*ByteBuffer*/) throws IOException {
tikhomirov@9: 		MessageDigest alg = getSHA1();
tikhomirov@9: 		byte[] buf = new byte[1024];
tikhomirov@9: 		int c;
tikhomirov@9: 		while ((c = is.read(buf)) != -1) {
tikhomirov@9: 			alg.update(buf, 0, c);
tikhomirov@9: 		}
tikhomirov@42: 		digest = alg.digest();
tikhomirov@42: 		return this;
tikhomirov@9: 	}
tikhomirov@9: 
tikhomirov@31: 	public static String toHexString(byte[] data, final int offset, final int count) {
tikhomirov@9: 		char[] result = new char[count << 1];
tikhomirov@9: 		final String hexDigits = "0123456789abcdef";
tikhomirov@9: 		final int end = offset+count;
tikhomirov@9: 		for (int i = offset, j = 0; i < end; i++) {
tikhomirov@9: 			result[j++] = hexDigits.charAt((data[i] >>> 4) & 0x0F);
tikhomirov@9: 			result[j++] = hexDigits.charAt(data[i] & 0x0F);
tikhomirov@9: 		}
tikhomirov@9: 		return new String(result);
tikhomirov@9: 	}
tikhomirov@9: }