--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/core/Nodeid.java	Mon Jan 24 03:14:45 2011 +0100
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2010-2011 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@svnkit.com
+ */
+package org.tmatesoft.hg.core;
+
+import static org.tmatesoft.hg.internal.DigestHelper.toHexString;
+
+import java.util.Arrays;
+
+
+
+/**
+ * A 20-bytes (40 characters) long hash value to identify a revision.
+ * @see http://mercurial.selenic.com/wiki/Nodeid
+ *
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ *
+ */
+public final class Nodeid {
+	
+	/**
+	 * <b>nullid</b>, empty root revision.
+	 */
+	public static final Nodeid NULL = new Nodeid(new byte[20], false);
+
+	private final byte[] binaryData; 
+
+	/**
+	 * @param binaryRepresentation - array of exactly 20 bytes
+	 * @param shallClone - true if array is subject to future modification and shall be copied, not referenced 
+	 */
+	public Nodeid(byte[] binaryRepresentation, boolean shallClone) {
+		// 5 int fields => 32 bytes
+		// byte[20] => 48 bytes
+		if (binaryRepresentation == null || binaryRepresentation.length != 20) {
+			throw new IllegalArgumentException();
+		}
+		this.binaryData = shallClone ? binaryRepresentation.clone() : binaryRepresentation;
+	}
+
+	@Override
+	public int hashCode() {
+		// digest (part thereof) seems to be nice candidate for the hashCode
+		byte[] b = binaryData;
+		return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
+	}
+	
+	@Override
+	public boolean equals(Object o) {
+		if (o instanceof Nodeid) {
+			return Arrays.equals(this.binaryData, ((Nodeid) o).binaryData);
+		}
+		return false;
+	}
+
+	public boolean equalsTo(byte[] buf) {
+		return Arrays.equals(this.binaryData, buf);
+	}
+	
+	@Override
+	public String toString() {
+		// XXX may want to output just single 0 for the NULL id?
+		return toHexString(binaryData, 0, binaryData.length);
+	}
+
+	public String shortNotation() {
+		return toHexString(binaryData, 0, 6);
+	}
+	
+	public boolean isNull() {
+		if (this == NULL) {
+			return true;
+		}
+		for (int i = 0; i < 20; i++) {
+			if (this.binaryData[i] != 0) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	// copy 
+	public byte[] toByteArray() {
+		return binaryData.clone();
+	}
+
+	// primary difference with cons is handling of NULL id (this method returns constant)
+	// always makes a copy of an array passed
+	public static Nodeid fromBinary(byte[] binaryRepresentation, int offset) {
+		if (binaryRepresentation == null || binaryRepresentation.length - offset < 20) {
+			throw new IllegalArgumentException();
+		}
+		int i = 0;
+		while (i < 20 && binaryRepresentation[offset+i] == 0) i++;
+		if (i == 20) {
+			return NULL;
+		}
+		if (offset == 0 && binaryRepresentation.length == 20) {
+			return new Nodeid(binaryRepresentation, true);
+		}
+		byte[] b = new byte[20]; // create new instance if no other reasonable guesses possible
+		System.arraycopy(binaryRepresentation, offset, b, 0, 20);
+		return new Nodeid(b, false);
+	}
+
+	public static Nodeid fromAscii(byte[] asciiRepresentation, int offset, int length) {
+		if (length != 40) {
+			throw new IllegalArgumentException();
+		}
+		byte[] data = new byte[20];
+		boolean zeroBytes = true;
+		for (int i = 0, j = offset; i < data.length; i++) {
+			int hiNibble = Character.digit(asciiRepresentation[j++], 16);
+			int lowNibble = Character.digit(asciiRepresentation[j++], 16);
+			byte b = (byte) (((hiNibble << 4) | lowNibble) & 0xFF);
+			data[i] = b;
+			zeroBytes = zeroBytes && b == 0;
+		}
+		if (zeroBytes) {
+			return NULL;
+		}
+		return new Nodeid(data, false);
+	}
+}