--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hg4j/src/main/java/org/tmatesoft/hg/internal/DataAccess.java	Tue May 10 10:52:53 2011 +0200
@@ -0,0 +1,102 @@
+/*
+ * 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@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+/**
+ * relevant parts of DataInput, non-stream nature (seek operation), explicit check for end of data.
+ * convenient skip (+/- bytes)
+ * Primary goal - effective file read, so that clients don't need to care whether to call few 
+ * distinct getInt() or readBytes(totalForFewInts) and parse themselves instead in an attempt to optimize.  
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class DataAccess {
+	public boolean isEmpty() {
+		return true;
+	}
+	public int length() {
+		return 0;
+	}
+	/**
+	 * get this instance into initial state
+	 * @throws IOException
+	 * @return <code>this</code> for convenience
+	 */
+	public DataAccess reset() throws IOException {
+		// nop, empty instance is always in the initial state
+		return this;
+	}
+	// absolute positioning
+	public void seek(int offset) throws IOException {
+		throw new UnsupportedOperationException();
+	}
+	// relative positioning
+	public void skip(int bytes) throws IOException {
+		throw new UnsupportedOperationException();
+	}
+	// shall be called once this object no longer needed
+	public void done() {
+		// no-op in this empty implementation
+	}
+	public int readInt() throws IOException {
+		byte[] b = new byte[4];
+		readBytes(b, 0, 4);
+		return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
+	}
+	public long readLong() throws IOException {
+		byte[] b = new byte[8];
+		readBytes(b, 0, 8);
+		int i1 = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
+		int i2 = b[4] << 24 | (b[5] & 0xFF) << 16 | (b[6] & 0xFF) << 8 | (b[7] & 0xFF);
+		return ((long) i1) << 32 | ((long) i2 & 0xFFFFFFFFl);
+	}
+	public void readBytes(byte[] buf, int offset, int length) throws IOException {
+		throw new UnsupportedOperationException();
+	}
+	// reads bytes into ByteBuffer, up to its limit or total data length, whichever smaller
+	// FIXME perhaps, in DataAccess paradigm (when we read known number of bytes, we shall pass specific byte count to read) 
+	public void readBytes(ByteBuffer buf) throws IOException {
+//		int toRead = Math.min(buf.remaining(), (int) length());
+//		if (buf.hasArray()) {
+//			readBytes(buf.array(), buf.arrayOffset(), toRead);
+//		} else {
+//			byte[] bb = new byte[toRead];
+//			readBytes(bb, 0, bb.length);
+//			buf.put(bb);
+//		}
+		// FIXME optimize to read as much as possible at once
+		while (!isEmpty() && buf.hasRemaining()) {
+			buf.put(readByte());
+		}
+	}
+	public byte readByte() throws IOException {
+		throw new UnsupportedOperationException();
+	}
+
+	// XXX decide whether may or may not change position in the DataAccess
+	// FIXME exception handling is not right, just for the sake of quick test
+	public byte[] byteArray() throws IOException {
+		reset();
+		byte[] rv = new byte[length()];
+		readBytes(rv, 0, rv.length);
+		return rv;
+	}
+}