tcpdatabuffer.java

来自「纯java操作系统jnode,安装简单和操作简单的个人使用的Java操作系统」· Java 代码 · 共 132 行

/*
 * $Id: TCPDataBuffer.java,v 1.1 2003/11/25 11:52:23 epr Exp $
 */
package org.jnode.net.ipv4.tcp;

import org.jnode.net.SocketBuffer;

/**
 * @author Ewout Prangsma ([e-mail])
 */
public class TCPDataBuffer {

	private final byte[] data;
	private final int length;
	private int used;

	/**
	 * Create a new instance
	 * 
	 * @param length
	 */
	public TCPDataBuffer(int length) {
		this.data = new byte[length];
		this.length = length;
		this.used = 0;
	}

	/**
	 * Create a socketbuffer for a given portion of this databuffer.
	 * 
	 * @param offset
	 * @param length
	 * @return The created buffer
	 */
	public SocketBuffer createSocketBuffer(int offset, int length) {
		if ((offset < 0) || (offset >= used)) {
			throw new IndexOutOfBoundsException("offset " + offset);
		}
		if ((length < 0) || (offset + length > used)) {
			throw new IndexOutOfBoundsException("offset + length" + offset + "+" + length);
		}
		return new SocketBuffer(data, offset, length);
	}

	/**
	 * Remove the first count byte from this buffer
	 * 
	 * @param count
	 */
	public void pull(int count) {
		if ((count < 0) || (count > used)) {
			// Avoid errors in SYN & FIN situations
			// TODO create a better solution for this
			if (count > 2) {
				throw new IllegalArgumentException("count " + count);
			}
		} else {
			used -= count;
			System.arraycopy(data, count, data, 0, used);
		}
	}

	/**
	 * Add the given data to this buffer.
	 * 
	 * @param src
	 * @param srcOffset
	 * @param length
	 * @return The offset of the added data within the buffer.
	 */
	public int add(byte[] src, int srcOffset, int length) {
		if (length > getFreeSize()) {
			throw new IllegalArgumentException("Not enough free space");
		}
		final int dstOffset = this.used;
		System.arraycopy(src, srcOffset, this.data, dstOffset, length);
		this.used += length;
		return dstOffset;
	}

	/**
	 * Add the given data to this buffer.
	 * 
	 * @return The offset of the added data within the buffer.
	 */
	public int add(SocketBuffer skbuf, int index, int length) {
		if (length > getFreeSize()) {
			throw new IllegalArgumentException("Not enough free space");
		}
		final int dstOffset = this.used;
		skbuf.get(this.data, dstOffset, index, length);
		this.used += length;
		return dstOffset;
	}

	/**
	 * @return Returns the length.
	 */
	public final int getLength() {
		return this.length;
	}

	/**
	 * @return Returns the used.
	 */
	public final int getUsed() {
		return this.used;
	}

	/**
	 * Gets the number of free bytes in this buffer
	 */
	public final int getFreeSize() {
		return length - used;
	}

	/**
	 * Read data from the start of this buffer and remove it.
	 * 
	 * @param b
	 * @param off
	 * @param len
	 * @return The number of bytes read
	 */
	public int read(byte[] b, int off, int len) {
		len = Math.min(used, len);
		System.arraycopy(data, 0, b, off, len);
		pull(len);
		return len;
	}
}