/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
 * 
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This software 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 * USA.
 */

//
// A ZlibInStream reads from a zlib.io.InputStream
//

public class ZlibInStream extends InStream {

	static final int defaultBufSize = 16384;

	public ZlibInStream(int bufSize_) {
		bufSize = bufSize_;
		b = new byte[bufSize];
		ptr = end = ptrOffset = 0;
		inflater = new java.util.zip.Inflater();
	}

	public ZlibInStream() {
		this(defaultBufSize);
	}

	public void setUnderlying(InStream is, int bytesIn_) {
		underlying = is;
		bytesIn = bytesIn_;
		ptr = end = 0;
	}

	public void reset() throws Exception {
		ptr = end = 0;
		if (underlying == null)
			return;

		while (bytesIn > 0) {
			decompress();
			end = 0; // throw away any data
		}
		underlying = null;
	}

	public int pos() {
		return ptrOffset + ptr;
	}

	protected int overrun(int itemSize, int nItems) throws Exception {
		if (itemSize > bufSize)
			throw new Exception("ZlibInStream overrun: max itemSize exceeded");
		if (underlying == null)
			throw new Exception("ZlibInStream overrun: no underlying stream");

		if (end - ptr != 0)
			System.arraycopy(b, ptr, b, 0, end - ptr);

		ptrOffset += ptr;
		end -= ptr;
		ptr = 0;

		while (end < itemSize) {
			decompress();
		}

		if (itemSize * nItems > end)
			nItems = end / itemSize;

		return nItems;
	}

	// decompress() calls the decompressor once. Note that this won't
	// necessarily generate any output data - it may just consume some input
	// data. Returns false if wait is false and we would block on the underlying
	// stream.

	private void decompress() throws Exception {
		try {
			underlying.check(1);
			int avail_in = underlying.getend() - underlying.getptr();
			if (avail_in > bytesIn)
				avail_in = bytesIn;

			if (inflater.needsInput()) {
				inflater.setInput(underlying.getbuf(), underlying.getptr(),
						avail_in);
			}

			int n = inflater.inflate(b, end, bufSize - end);
			end += n;
			if (inflater.needsInput()) {
				bytesIn -= avail_in;
				underlying.setptr(underlying.getptr() + avail_in);
			}
		} catch (java.util.zip.DataFormatException e) {
			throw new Exception("ZlibInStream: inflate failed");
		}
	}

	private InStream underlying;
	private int bufSize;
	private int ptrOffset;
	private java.util.zip.Inflater inflater;
	private int bytesIn;
}