kitaev@213: /*
kitaev@213:  * Copyright (c) 2010-2011 TMate Software Ltd
kitaev@213:  *  
kitaev@213:  * This program is free software; you can redistribute it and/or modify
kitaev@213:  * it under the terms of the GNU General Public License as published by
kitaev@213:  * the Free Software Foundation; version 2 of the License.
kitaev@213:  *
kitaev@213:  * This program is distributed in the hope that it will be useful,
kitaev@213:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
kitaev@213:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
kitaev@213:  * GNU General Public License for more details.
kitaev@213:  *
kitaev@213:  * For information on how to redistribute this software under
kitaev@213:  * the terms of a license other than GNU General Public License
kitaev@213:  * contact TMate Software at support@hg4j.com
kitaev@213:  */
kitaev@213: package org.tmatesoft.hg.internal;
kitaev@213: 
kitaev@213: import java.io.IOException;
kitaev@213: import java.nio.ByteBuffer;
kitaev@213: 
kitaev@213: /**
kitaev@213:  * relevant parts of DataInput, non-stream nature (seek operation), explicit check for end of data.
kitaev@213:  * convenient skip (+/- bytes)
kitaev@213:  * Primary goal - effective file read, so that clients don't need to care whether to call few 
kitaev@213:  * distinct getInt() or readBytes(totalForFewInts) and parse themselves instead in an attempt to optimize.  
kitaev@213:  * 
kitaev@213:  * @author Artem Tikhomirov
kitaev@213:  * @author TMate Software Ltd.
kitaev@213:  */
kitaev@213: public class DataAccess {
kitaev@213: 	public boolean isEmpty() {
kitaev@213: 		return true;
kitaev@213: 	}
kitaev@213: 	public int length() {
kitaev@213: 		return 0;
kitaev@213: 	}
kitaev@213: 	/**
kitaev@213: 	 * get this instance into initial state
kitaev@213: 	 * @throws IOException
kitaev@213: 	 * @return <code>this</code> for convenience
kitaev@213: 	 */
kitaev@213: 	public DataAccess reset() throws IOException {
kitaev@213: 		// nop, empty instance is always in the initial state
kitaev@213: 		return this;
kitaev@213: 	}
kitaev@213: 	// absolute positioning
kitaev@213: 	public void seek(int offset) throws IOException {
kitaev@213: 		throw new UnsupportedOperationException();
kitaev@213: 	}
kitaev@213: 	// relative positioning
kitaev@213: 	public void skip(int bytes) throws IOException {
kitaev@213: 		throw new UnsupportedOperationException();
kitaev@213: 	}
kitaev@213: 	// shall be called once this object no longer needed
kitaev@213: 	public void done() {
kitaev@213: 		// no-op in this empty implementation
kitaev@213: 	}
kitaev@213: 	public int readInt() throws IOException {
kitaev@213: 		byte[] b = new byte[4];
kitaev@213: 		readBytes(b, 0, 4);
kitaev@213: 		return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
kitaev@213: 	}
kitaev@213: 	public long readLong() throws IOException {
kitaev@213: 		byte[] b = new byte[8];
kitaev@213: 		readBytes(b, 0, 8);
kitaev@213: 		int i1 = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
kitaev@213: 		int i2 = b[4] << 24 | (b[5] & 0xFF) << 16 | (b[6] & 0xFF) << 8 | (b[7] & 0xFF);
kitaev@213: 		return ((long) i1) << 32 | ((long) i2 & 0xFFFFFFFFl);
kitaev@213: 	}
kitaev@213: 	public void readBytes(byte[] buf, int offset, int length) throws IOException {
kitaev@213: 		throw new UnsupportedOperationException();
kitaev@213: 	}
kitaev@213: 	// reads bytes into ByteBuffer, up to its limit or total data length, whichever smaller
kitaev@213: 	// FIXME perhaps, in DataAccess paradigm (when we read known number of bytes, we shall pass specific byte count to read) 
kitaev@213: 	public void readBytes(ByteBuffer buf) throws IOException {
kitaev@213: //		int toRead = Math.min(buf.remaining(), (int) length());
kitaev@213: //		if (buf.hasArray()) {
kitaev@213: //			readBytes(buf.array(), buf.arrayOffset(), toRead);
kitaev@213: //		} else {
kitaev@213: //			byte[] bb = new byte[toRead];
kitaev@213: //			readBytes(bb, 0, bb.length);
kitaev@213: //			buf.put(bb);
kitaev@213: //		}
kitaev@213: 		// FIXME optimize to read as much as possible at once
kitaev@213: 		while (!isEmpty() && buf.hasRemaining()) {
kitaev@213: 			buf.put(readByte());
kitaev@213: 		}
kitaev@213: 	}
kitaev@213: 	public byte readByte() throws IOException {
kitaev@213: 		throw new UnsupportedOperationException();
kitaev@213: 	}
kitaev@213: 
kitaev@213: 	// XXX decide whether may or may not change position in the DataAccess
kitaev@213: 	// FIXME exception handling is not right, just for the sake of quick test
kitaev@213: 	public byte[] byteArray() throws IOException {
kitaev@213: 		reset();
kitaev@213: 		byte[] rv = new byte[length()];
kitaev@213: 		readBytes(rv, 0, rv.length);
kitaev@213: 		return rv;
kitaev@213: 	}
kitaev@213: }