messageinputstream.java

一个用Java开发的Web邮局

/*
 * MessageInputStream.java
 * Copyright (C) 1999 dog <[e-mail]>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * You may retrieve the latest version of this library from
 * http://www.dog.net.uk/knife/
 */

package dog.mail.util;

import java.io.*;

/**
 * A utility class for feeding message contents to messages.
 *
 * @author [e-mail]
 * @version 1.0
 */
public class MessageInputStream extends FilterInputStream {

	/**
	 * The stream termination octet.
	 */
	public static final int END = 46;
	
	/**
	 * The line termination octet.
	 */
	public static final int LF = 10;
	
	boolean done = false, debug = false;
	int last = -1; // register for the last octet read
	int bufsize; // the buffer size for the pushback (CRLF) stream
	
	/**
	 * Constructs a message input stream connected to the specified pushback input stream.
	 */
	public MessageInputStream(PushbackInputStream in) {
		super(in);
	}

	/**
	 * Constructs a message input stream connected to the specified pushback input stream.
	 */
	public MessageInputStream(PushbackInputStream in, boolean debug) {
		super(in);
		this.debug = debug;
	}

	/**
	 * Reads the next byte of data from this message input stream.
	 * Returns -1 if the end of the message stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read() throws IOException {
		if (done) return -1;
		int ch = in.read();
		if (ch==END && last==LF) {
			int ch2 = in.read(); // look ahead for LF
			if (ch2==LF) {
				done = true;
				return -1; // swallow the END and LF
			} else
				((PushbackInputStream)in).unread(ch2);
		}
		last = ch;
		return ch;
	}
	
	/**
	 * Reads up to b.length bytes of data from this input stream into
	 * an array of bytes.
	 * Returns -1 if the end of the stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read(byte[] b) throws IOException {
		return read(b, 0, b.length);
	}
	
	/**
	 * Reads up to len bytes of data from this input stream into an
	 * array of bytes, starting at the specified offset.
	 * Returns -1 if the end of the stream has been reached.
	 * @exception IOException if an I/O error occurs
	 */
	public int read(byte[] b, int off, int len) throws IOException {
		if (done) return -1;
		int l = in.read(b, off, len);
		if (debug)
			System.err.println("DEBUG: stream: read "+len+" bytes");
		int i = indexOfEnd(b, off, l);
		if (i>=0) {
			((PushbackInputStream)in).unread(b, i+off+2, (l-(i+2)));
			done = true;
			return i;
		} else if (b[l-1]==LF) {
			((PushbackInputStream)in).unread(b, l-1, 1);
			Thread.yield();
			return l - 1;
		} else if ((l >= 2) && (b[l-2]==LF && b[l-1]==END)) {
			((PushbackInputStream)in).unread(b, l-2, 2);
			Thread.yield();
			return l - 2;
		}
		return l;
	}
	// Discover the index of END in a byte array.
	int indexOfEnd(byte[] b, int off, int len) {
		for (int i=off+2; i<(off+len); i++)
			if (b[i]==LF && b[i-1]==END && b[i-2]==LF)
				return i-off-1;
		return -1;
	}
	
}