Import TechBot

svn path=/trunk/; revision=13064

irc/TechBot/Compression/Streams/StreamManipulator.cs

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+// StreamManipulator.cs
+// Copyright (C) 2001 Mike Krueger
+//
+// This file was translated from java, it was part of the GNU Classpath
+// Copyright (C) 2001 Free Software Foundation, Inc.
+//
+// This program 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 program 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 program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+//
+// Linking this library statically or dynamically with other modules is
+// making a combined work based on this library.  Thus, the terms and
+// conditions of the GNU General Public License cover the whole
+// combination.
+// 
+// As a special exception, the copyright holders of this library give you
+// permission to link this library with independent modules to produce an
+// executable, regardless of the license terms of these independent
+// modules, and to copy and distribute the resulting executable under
+// terms of your choice, provided that you also meet, for each linked
+// independent module, the terms and conditions of the license of that
+// module.  An independent module is a module which is not derived from
+// or based on this library.  If you modify this library, you may extend
+// this exception to your version of the library, but you are not
+// obligated to do so.  If you do not wish to do so, delete this
+// exception statement from your version.
+
+using System;
+
+namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams 
+{
+	
+	/// <summary>
+	/// This class allows us to retrieve a specified amount of bits from
+	/// the input buffer, as well as copy big byte blocks.
+	///
+	/// It uses an int buffer to store up to 31 bits for direct
+	/// manipulation.  This guarantees that we can get at least 16 bits,
+	/// but we only need at most 15, so this is all safe.
+	///
+	/// There are some optimizations in this class, for example, you must
+	/// never peek more then 8 bits more than needed, and you must first
+	/// peek bits before you may drop them.  This is not a general purpose
+	/// class but optimized for the behaviour of the Inflater.
+	///
+	/// authors of the original java version : John Leuner, Jochen Hoenicke
+	/// </summary>
+	public class StreamManipulator
+	{
+		private byte[] window;
+		private int window_start = 0;
+		private int window_end = 0;
+		
+		private uint buffer = 0;
+		private int bits_in_buffer = 0;
+		
+		/// <summary>
+		/// Get the next n bits but don't increase input pointer.  n must be
+		/// less or equal 16 and if you if this call succeeds, you must drop
+		/// at least n-8 bits in the next call.
+		/// </summary>
+		/// <returns>
+		/// the value of the bits, or -1 if not enough bits available.  */
+		/// </returns>
+		public int PeekBits(int n)
+		{
+			if (bits_in_buffer < n) {
+				if (window_start == window_end) {
+					return -1; // ok
+				}
+				buffer |= (uint)((window[window_start++] & 0xff |
+				                 (window[window_start++] & 0xff) << 8) << bits_in_buffer);
+				bits_in_buffer += 16;
+			}
+			return (int)(buffer & ((1 << n) - 1));
+		}
+		
+		/// <summary>
+		/// Drops the next n bits from the input.  You should have called peekBits
+		/// with a bigger or equal n before, to make sure that enough bits are in
+		/// the bit buffer.
+		/// </summary>
+		public void DropBits(int n)
+		{
+			buffer >>= n;
+			bits_in_buffer -= n;
+		}
+		
+		/// <summary>
+		/// Gets the next n bits and increases input pointer.  This is equivalent
+		/// to peekBits followed by dropBits, except for correct error handling.
+		/// </summary>
+		/// <returns>
+		/// the value of the bits, or -1 if not enough bits available.
+		/// </returns>
+		public int GetBits(int n)
+		{
+			int bits = PeekBits(n);
+			if (bits >= 0) {
+				DropBits(n);
+			}
+			return bits;
+		}
+		
+		/// <summary>
+		/// Gets the number of bits available in the bit buffer.  This must be
+		/// only called when a previous peekBits() returned -1.
+		/// </summary>
+		/// <returns>
+		/// the number of bits available.
+		/// </returns>
+		public int AvailableBits {
+			get {
+				return bits_in_buffer;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the number of bytes available.
+		/// </summary>
+		/// <returns>
+		/// the number of bytes available.
+		/// </returns>
+		public int AvailableBytes {
+			get {
+				return window_end - window_start + (bits_in_buffer >> 3);
+			}
+		}
+		
+		/// <summary>
+		/// Skips to the next byte boundary.
+		/// </summary>
+		public void SkipToByteBoundary()
+		{
+			buffer >>= (bits_in_buffer & 7);
+			bits_in_buffer &= ~7;
+		}
+		
+		public bool IsNeedingInput {
+			get {
+				return window_start == window_end;
+			}
+		}
+		
+		/// <summary>
+		/// Copies length bytes from input buffer to output buffer starting
+		/// at output[offset].  You have to make sure, that the buffer is
+		/// byte aligned.  If not enough bytes are available, copies fewer
+		/// bytes.
+		/// </summary>
+		/// <param name="output">
+		/// the buffer.
+		/// </param>
+		/// <param name="offset">
+		/// the offset in the buffer.
+		/// </param>
+		/// <param name="length">
+		/// the length to copy, 0 is allowed.
+		/// </param>
+		/// <returns>
+		/// the number of bytes copied, 0 if no byte is available.
+		/// </returns>
+		public int CopyBytes(byte[] output, int offset, int length)
+		{
+			if (length < 0) {
+				throw new ArgumentOutOfRangeException("length negative");
+			}
+			if ((bits_in_buffer & 7) != 0) {
+				/* bits_in_buffer may only be 0 or 8 */
+				throw new InvalidOperationException("Bit buffer is not aligned!");
+			}
+			
+			int count = 0;
+			while (bits_in_buffer > 0 && length > 0) {
+				output[offset++] = (byte) buffer;
+				buffer >>= 8;
+				bits_in_buffer -= 8;
+				length--;
+				count++;
+			}
+			if (length == 0) {
+				return count;
+			}
+			
+			int avail = window_end - window_start;
+			if (length > avail) {
+				length = avail;
+			}
+			System.Array.Copy(window, window_start, output, offset, length);
+			window_start += length;
+			
+			if (((window_start - window_end) & 1) != 0) {
+				/* We always want an even number of bytes in input, see peekBits */
+				buffer = (uint)(window[window_start++] & 0xff);
+				bits_in_buffer = 8;
+			}
+			return count + length;
+		}
+		
+		public StreamManipulator()
+		{
+		}
+		
+		public void Reset()
+		{
+			buffer = (uint)(window_start = window_end = bits_in_buffer = 0);
+		}
+		
+		public void SetInput(byte[] buf, int off, int len)
+		{
+			if (window_start < window_end) {
+				throw new InvalidOperationException("Old input was not completely processed");
+			}
+			
+			int end = off + len;
+			
+			/* We want to throw an ArrayIndexOutOfBoundsException early.  The
+			* check is very tricky: it also handles integer wrap around.
+			*/
+			if (0 > off || off > end || end > buf.Length) {
+				throw new ArgumentOutOfRangeException();
+			}
+			
+			if ((len & 1) != 0) {
+				/* We always want an even number of bytes in input, see peekBits */
+				buffer |= (uint)((buf[off++] & 0xff) << bits_in_buffer);
+				bits_in_buffer += 8;
+			}
+			
+			window = buf;
+			window_start = off;
+			window_end = end;
+		}
+	}
+}