--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/tmate/hgkit/ll/DigestHelper.java	Sat Dec 25 04:45:59 2010 +0100
@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) 2010 Artem Tikhomirov 
+ */
+package com.tmate.hgkit.ll;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ *
+ * @author artem
+ */
+public class DigestHelper {
+	private MessageDigest sha1;
+
+	public DigestHelper() {
+	}
+	
+	private MessageDigest getSHA1() {
+		if (sha1 == null) {
+			try {
+				sha1 = MessageDigest.getInstance("SHA-1");
+			} catch (NoSuchAlgorithmException ex) {
+				// could hardly happen, JDK from Sun always has sha1.
+				ex.printStackTrace(); // FIXME log error
+			}
+		}
+		return sha1;
+	}
+
+	// XXX perhaps, digest functions should throw an exception, as it's caller responsibility to deal with eof, etc
+	public String sha1(byte[] data) {
+		MessageDigest alg = getSHA1();
+		byte[] digest = alg.digest(data);
+		assert digest.length == 20;
+		return toHexString(digest, 0, 20);
+	}
+
+	public byte[] sha1(InputStream is /*ByteBuffer*/) throws IOException {
+		MessageDigest alg = getSHA1();
+		byte[] buf = new byte[1024];
+		int c;
+		while ((c = is.read(buf)) != -1) {
+			alg.update(buf, 0, c);
+		}
+		byte[] digest = alg.digest();
+		return digest;
+	}
+
+	public String toHexString(byte[] data, final int offset, final int count) {
+		char[] result = new char[count << 1];
+		final String hexDigits = "0123456789abcdef";
+		final int end = offset+count;
+		for (int i = offset, j = 0; i < end; i++) {
+			result[j++] = hexDigits.charAt((data[i] >>> 4) & 0x0F);
+			result[j++] = hexDigits.charAt(data[i] & 0x0F);
+		}
+		return new String(result);
+	}
+}