tikhomirov@10: /*
tikhomirov@10:  * Copyright (c) 2010 Artem Tikhomirov 
tikhomirov@10:  */
tikhomirov@10: package com.tmate.hgkit.fs;
tikhomirov@10: 
tikhomirov@10: import java.io.IOException;
tikhomirov@10: 
tikhomirov@10: /**
tikhomirov@10:  * relevant parts of DataInput, non-stream nature (seek operation), explicit check for end of data.
tikhomirov@10:  * convenient skip (+/- bytes)
tikhomirov@10:  * Primary goal - effective file read, so that clients don't need to care whether to call few 
tikhomirov@51:  * distinct getInt() or readBytes(totalForFewInts) and parse themselves instead in an attempt to optimize.
tikhomirov@51:  * Name: ByteSource? DataSource, DataInput, ByteInput 
tikhomirov@10:  */
tikhomirov@10: public class DataAccess {
tikhomirov@10: 	public boolean isEmpty() {
tikhomirov@10: 		return true;
tikhomirov@10: 	}
tikhomirov@51: 	public long length() {
tikhomirov@51: 		return 0;
tikhomirov@51: 	}
tikhomirov@51: 	// get this instance into initial state
tikhomirov@51: 	public void reset() throws IOException {
tikhomirov@51: 		// nop, empty instance is always in the initial state
tikhomirov@51: 	}
tikhomirov@10: 	// absolute positioning
tikhomirov@10: 	public void seek(long offset) throws IOException {
tikhomirov@10: 		throw new UnsupportedOperationException();
tikhomirov@10: 	}
tikhomirov@10: 	// relative positioning
tikhomirov@10: 	public void skip(int bytes) throws IOException {
tikhomirov@10: 		throw new UnsupportedOperationException();
tikhomirov@10: 	}
tikhomirov@10: 	// shall be called once this object no longer needed
tikhomirov@10: 	public void done() {
tikhomirov@10: 		// no-op in this empty implementation
tikhomirov@10: 	}
tikhomirov@10: 	public int readInt() throws IOException {
tikhomirov@10: 		byte[] b = new byte[4];
tikhomirov@10: 		readBytes(b, 0, 4);
tikhomirov@10: 		return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
tikhomirov@10: 	}
tikhomirov@10: 	public long readLong() throws IOException {
tikhomirov@10: 		byte[] b = new byte[8];
tikhomirov@10: 		readBytes(b, 0, 8);
tikhomirov@10: 		int i1 = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
tikhomirov@10: 		int i2 = b[4] << 24 | (b[5] & 0xFF) << 16 | (b[6] & 0xFF) << 8 | (b[7] & 0xFF);
tikhomirov@10: 		return ((long) i1) << 32 | ((long) i2 & 0xFFFFFFFF);
tikhomirov@10: 	}
tikhomirov@10: 	public void readBytes(byte[] buf, int offset, int length) throws IOException {
tikhomirov@10: 		throw new UnsupportedOperationException();
tikhomirov@10: 	}
tikhomirov@10: 	public byte readByte() throws IOException {
tikhomirov@10: 		throw new UnsupportedOperationException();
tikhomirov@10: 	}
tikhomirov@51: 
tikhomirov@51: 	// XXX decide whether may or may not change position in the DataAccess
tikhomirov@51: 	// FIXME exception handling is not right, just for the sake of quick test
tikhomirov@51: 	public byte[] byteArray() {
tikhomirov@51: 		byte[] rv = new byte[(int) length()];
tikhomirov@51: 		try {
tikhomirov@51: 			reset();
tikhomirov@51: 			readBytes(rv, 0, rv.length);
tikhomirov@51: 		} catch (IOException ex) {
tikhomirov@51: 			ex.printStackTrace();
tikhomirov@51: 		}
tikhomirov@51: 		return rv;
tikhomirov@51: 	}
tikhomirov@10: }