databuffer.java

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package org.flexdock.docking.drag.outline.x11;
/*
 * Created on Aug 29, 2004
 */

/**
 * @author Christopher Butler
 */
public class DataBuffer {
	public static final int DEFAULT_BUFFER_SIZE = 256;
	private byte[] dataBuffer;
	private int bufferOffset;
	
	public DataBuffer() {
		this(DEFAULT_BUFFER_SIZE);
	}
	
	public DataBuffer(int initialBufferSize) {
		dataBuffer = new byte[initialBufferSize];
	}
	
	public DataBuffer(byte[] rawData) {
		dataBuffer = new byte[rawData.length];
		bufferOffset = rawData.length;
		System.arraycopy(rawData, 0, dataBuffer, 0, bufferOffset);
	}
	
	public void appendByte(int data) {
		ensureCapacity(1);
		dataBuffer[bufferOffset] = (byte)data;
		bufferOffset++;
	}
	
	public void appendTwoBytes(int data) {
		byte[] bytes = new byte[2];
		bytes[0] = (byte) (data>>8 & 0xff);
		bytes[1] = (byte) (data & 0xff);
		appendBytesImpl(bytes);
	}
	
	public void appendFourBytes(int data) {
		byte[] bytes = new byte[4];
		bytes[0] = (byte) ((data >> 24) & 0xff);
		bytes[1] = (byte) ((data >> 16) & 0xff);
		bytes[2] = (byte) ((data >> 8) & 0xff);
		bytes[3] = (byte) (data & 0xff);
		appendBytesImpl(bytes);
	}
	
	private void appendBytesImpl(byte[] formatted) {
		for(int i=0; i<formatted.length; i++) {
			appendByte(formatted[i]);
		}
	}
	
	private void ensureCapacity(int dataSize) {
		if(bufferOffset + dataSize >= dataBuffer.length) {
			byte[] tmp = new byte[dataBuffer.length*2];
			System.arraycopy(dataBuffer, 0, tmp, 0, dataBuffer.length);
			dataBuffer = tmp;
		}
	}
	
	public byte[] getBytes() {
		byte[] ret = new byte[bufferOffset];
		System.arraycopy(dataBuffer, 0, ret, 0, ret.length);
		return ret;
	}
	
	public int readByte(int offset) {
		return dataBuffer[offset] & 0xff;
	}
	
	public int readTwoBytes(int offset) {
		int b0 = readByte(offset) << 8;
		int b1 = readByte(offset+1);
		return b0 | b1;
	}
	
	public int readFourBytes(int offset) {
		int b0 = readByte(offset) << 24;
		int b1 = readByte(offset+1) << 16;
		int b2 = readByte(offset+2) << 8;
		int b3 = readByte(offset+3);
		return b0 | b1 | b2 | b3;
	}
	
	public byte[] getSubset(int offset, int length) {
		byte[] subset = new byte[length];
		System.arraycopy(dataBuffer, offset, subset, 0, length);
		return subset;
	}
	
	public DataBuffer getSubBuffer(int offset, int length) {
		byte[] subset = getSubset(offset, length);
		return new DataBuffer(subset);
	}
	
	public static int decode(byte[] data) {
		if(data==null || data.length==0)
			return -1;
		
		int shift = 8 * (data.length-1);
		int ret = 0;
		for(int i=0; i<data.length; i++) {
			int currVal =  (data[i] & 0xff) << shift;
			shift -= 8;
			ret = i==0? currVal: ret | currVal;
		}
		return ret;
	}
	
	public static byte[] encode(int data, int byteCount) {
		if(byteCount<0)
			return null;
		
		byte[] ret = new byte[byteCount];
		int shift = 8 * (byteCount-1);
		
		for(int i=0; i<byteCount; i++) {
			 ret[i] = (byte) ((data >> shift) & 0xff);
			 shift -= 8;
		}
		return ret;
	}
	
	public static int padLength(int len) {
		return (len + 3) & 0xfffffffc;
	}
}