root/trunk/Updater/ICSharpCode.SharpZipLib/Zip/Compression/Streams/OutputWindow.cs @ 597

// OutputWindow.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>
        /// Contains the output from the Inflation process.
        /// We need to have a window so that we can refer backwards into the output stream
        /// to repeat stuff.<br/>
        /// Author of the original java version : John Leuner
        /// </summary>
        public class OutputWindow
        {
                #region Constants
                const int WindowSize = 1 << 15;
                const int WindowMask = WindowSize - 1;
                #endregion
                
                #region Instance Fields
                byte[] window = new byte[WindowSize]; //The window is 2^15 bytes
                int windowEnd;
                int windowFilled;
                #endregion
                
                /// <summary>
                /// Write a byte to this output window
                /// </summary>
                /// <param name="value">value to write</param>
                /// <exception cref="InvalidOperationException">
                /// if window is full
                /// </exception>
                public void Write(int value)
                {
                        if (windowFilled++ == WindowSize) {
                                throw new InvalidOperationException("Window full");
                        }
                        window[windowEnd++] = (byte) value;
                        windowEnd &= WindowMask;
                }
                
                
                private void SlowRepeat(int repStart, int length, int distance)
                {
                        while (length-- > 0) {
                                window[windowEnd++] = window[repStart++];
                                windowEnd &= WindowMask;
                                repStart &= WindowMask;
                        }
                }
                
                /// <summary>
                /// Append a byte pattern already in the window itself
                /// </summary>
                /// <param name="length">length of pattern to copy</param>
                /// <param name="distance">distance from end of window pattern occurs</param>
                /// <exception cref="InvalidOperationException">
                /// If the repeated data overflows the window
                /// </exception>
                public void Repeat(int length, int distance)
                {
                        if ((windowFilled += length) > WindowSize) {
                                throw new InvalidOperationException("Window full");
                        }
                        
                        int repStart = (windowEnd - distance) & WindowMask;
                        int border = WindowSize - length;
                        if ( (repStart <= border) && (windowEnd < border) ) {
                                if (length <= distance) {
                                        System.Array.Copy(window, repStart, window, windowEnd, length);
                                        windowEnd += length;
                                } else {
                                        // We have to copy manually, since the repeat pattern overlaps.
                                        while (length-- > 0) {
                                                window[windowEnd++] = window[repStart++];
                                        }
                                }
                        } else {
                                SlowRepeat(repStart, length, distance);
                        }
                }
                
                /// <summary>
                /// Copy from input manipulator to internal window
                /// </summary>
                /// <param name="input">source of data</param>
                /// <param name="length">length of data to copy</param>
                /// <returns>the number of bytes copied</returns>
                public int CopyStored(StreamManipulator input, int length)
                {
                        length = Math.Min(Math.Min(length, WindowSize - windowFilled), input.AvailableBytes);
                        int copied;
                        
                        int tailLen = WindowSize - windowEnd;
                        if (length > tailLen) {
                                copied = input.CopyBytes(window, windowEnd, tailLen);
                                if (copied == tailLen) {
                                        copied += input.CopyBytes(window, 0, length - tailLen);
                                }
                        } else {
                                copied = input.CopyBytes(window, windowEnd, length);
                        }
                        
                        windowEnd = (windowEnd + copied) & WindowMask;
                        windowFilled += copied;
                        return copied;
                }
                
                /// <summary>
                /// Copy dictionary to window
                /// </summary>
                /// <param name="dictionary">source dictionary</param>
                /// <param name="offset">offset of start in source dictionary</param>
                /// <param name="length">length of dictionary</param>
                /// <exception cref="InvalidOperationException">
                /// If window isnt empty
                /// </exception>
                public void CopyDict(byte[] dictionary, int offset, int length)
                {
                        if ( dictionary == null ) {
                                throw new ArgumentNullException("dictionary");
                        }

                        if (windowFilled > 0) {
                                throw new InvalidOperationException();
                        }
                        
                        if (length > WindowSize) {
                                offset += length - WindowSize;
                                length = WindowSize;
                        }
                        System.Array.Copy(dictionary, offset, window, 0, length);
                        windowEnd = length & WindowMask;
                }

                /// <summary>
                /// Get remaining unfilled space in window
                /// </summary>
                /// <returns>Number of bytes left in window</returns>
                public int GetFreeSpace()
                {
                        return WindowSize - windowFilled;
                }
                
                /// <summary>
                /// Get bytes available for output in window
                /// </summary>
                /// <returns>Number of bytes filled</returns>
                public int GetAvailable()
                {
                        return windowFilled;
                }

                /// <summary>
                /// Copy contents of window to output
                /// </summary>
                /// <param name="output">buffer to copy to</param>
                /// <param name="offset">offset to start at</param>
                /// <param name="len">number of bytes to count</param>
                /// <returns>The number of bytes copied</returns>
                /// <exception cref="InvalidOperationException">
                /// If a window underflow occurs
                /// </exception>
                public int CopyOutput(byte[] output, int offset, int len)
                {
                        int copyEnd = windowEnd;
                        if (len > windowFilled) {
                                len = windowFilled;
                        } else {
                                copyEnd = (windowEnd - windowFilled + len) & WindowMask;
                        }
                        
                        int copied = len;
                        int tailLen = len - copyEnd;
                        
                        if (tailLen > 0) {
                                System.Array.Copy(window, WindowSize - tailLen, output, offset, tailLen);
                                offset += tailLen;
                                len = copyEnd;
                        }
                        System.Array.Copy(window, copyEnd - len, output, offset, len);
                        windowFilled -= copied;
                        if (windowFilled < 0) {
                                throw new InvalidOperationException();
                        }
                        return copied;
                }

                /// <summary>
                /// Reset by clearing window so <see cref="GetAvailable">GetAvailable</see> returns 0
                /// </summary>
                public void Reset()
                {
                        windowFilled = windowEnd = 0;
                }
        }
}