236 lines
7.2 KiB
C#
236 lines
7.2 KiB
C#
// OutputWindow.cs
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//
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// Copyright (C) 2001 Mike Krueger
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//
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// This file was translated from java, it was part of the GNU Classpath
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// Copyright (C) 2001 Free Software Foundation, Inc.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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//
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// Linking this library statically or dynamically with other modules is
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// making a combined work based on this library. Thus, the terms and
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// conditions of the GNU General Public License cover the whole
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// combination.
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//
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// As a special exception, the copyright holders of this library give you
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// permission to link this library with independent modules to produce an
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// executable, regardless of the license terms of these independent
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// modules, and to copy and distribute the resulting executable under
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// terms of your choice, provided that you also meet, for each linked
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// independent module, the terms and conditions of the license of that
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// module. An independent module is a module which is not derived from
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// or based on this library. If you modify this library, you may extend
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// this exception to your version of the library, but you are not
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// obligated to do so. If you do not wish to do so, delete this
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// exception statement from your version.
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using System;
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namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams
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{
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/// <summary>
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/// Contains the output from the Inflation process.
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/// We need to have a window so that we can refer backwards into the output stream
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/// to repeat stuff.<br/>
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/// Author of the original java version : John Leuner
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/// </summary>
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public class OutputWindow
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{
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#region Constants
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const int WindowSize = 1 << 15;
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const int WindowMask = WindowSize - 1;
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#endregion
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#region Instance Fields
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byte[] window = new byte[WindowSize]; //The window is 2^15 bytes
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int windowEnd;
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int windowFilled;
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#endregion
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/// <summary>
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/// Write a byte to this output window
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/// </summary>
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/// <param name="value">value to write</param>
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/// <exception cref="InvalidOperationException">
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/// if window is full
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/// </exception>
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public void Write(int value)
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{
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if (windowFilled++ == WindowSize) {
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throw new InvalidOperationException("Window full");
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}
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window[windowEnd++] = (byte) value;
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windowEnd &= WindowMask;
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}
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private void SlowRepeat(int repStart, int length, int distance)
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{
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while (length-- > 0) {
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window[windowEnd++] = window[repStart++];
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windowEnd &= WindowMask;
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repStart &= WindowMask;
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}
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}
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/// <summary>
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/// Append a byte pattern already in the window itself
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/// </summary>
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/// <param name="length">length of pattern to copy</param>
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/// <param name="distance">distance from end of window pattern occurs</param>
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/// <exception cref="InvalidOperationException">
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/// If the repeated data overflows the window
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/// </exception>
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public void Repeat(int length, int distance)
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{
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if ((windowFilled += length) > WindowSize) {
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throw new InvalidOperationException("Window full");
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}
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int repStart = (windowEnd - distance) & WindowMask;
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int border = WindowSize - length;
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if ( (repStart <= border) && (windowEnd < border) ) {
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if (length <= distance) {
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System.Array.Copy(window, repStart, window, windowEnd, length);
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windowEnd += length;
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} else {
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// We have to copy manually, since the repeat pattern overlaps.
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while (length-- > 0) {
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window[windowEnd++] = window[repStart++];
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}
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}
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} else {
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SlowRepeat(repStart, length, distance);
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}
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}
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/// <summary>
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/// Copy from input manipulator to internal window
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/// </summary>
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/// <param name="input">source of data</param>
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/// <param name="length">length of data to copy</param>
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/// <returns>the number of bytes copied</returns>
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public int CopyStored(StreamManipulator input, int length)
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{
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length = Math.Min(Math.Min(length, WindowSize - windowFilled), input.AvailableBytes);
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int copied;
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int tailLen = WindowSize - windowEnd;
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if (length > tailLen) {
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copied = input.CopyBytes(window, windowEnd, tailLen);
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if (copied == tailLen) {
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copied += input.CopyBytes(window, 0, length - tailLen);
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}
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} else {
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copied = input.CopyBytes(window, windowEnd, length);
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}
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windowEnd = (windowEnd + copied) & WindowMask;
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windowFilled += copied;
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return copied;
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}
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/// <summary>
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/// Copy dictionary to window
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/// </summary>
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/// <param name="dictionary">source dictionary</param>
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/// <param name="offset">offset of start in source dictionary</param>
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/// <param name="length">length of dictionary</param>
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/// <exception cref="InvalidOperationException">
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/// If window isnt empty
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/// </exception>
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public void CopyDict(byte[] dictionary, int offset, int length)
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{
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if ( dictionary == null ) {
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throw new ArgumentNullException("dictionary");
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}
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if (windowFilled > 0) {
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throw new InvalidOperationException();
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}
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if (length > WindowSize) {
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offset += length - WindowSize;
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length = WindowSize;
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}
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System.Array.Copy(dictionary, offset, window, 0, length);
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windowEnd = length & WindowMask;
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}
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/// <summary>
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/// Get remaining unfilled space in window
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/// </summary>
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/// <returns>Number of bytes left in window</returns>
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public int GetFreeSpace()
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{
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return WindowSize - windowFilled;
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}
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/// <summary>
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/// Get bytes available for output in window
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/// </summary>
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/// <returns>Number of bytes filled</returns>
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public int GetAvailable()
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{
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return windowFilled;
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}
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/// <summary>
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/// Copy contents of window to output
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/// </summary>
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/// <param name="output">buffer to copy to</param>
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/// <param name="offset">offset to start at</param>
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/// <param name="len">number of bytes to count</param>
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/// <returns>The number of bytes copied</returns>
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/// <exception cref="InvalidOperationException">
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/// If a window underflow occurs
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/// </exception>
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public int CopyOutput(byte[] output, int offset, int len)
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{
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int copyEnd = windowEnd;
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if (len > windowFilled) {
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len = windowFilled;
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} else {
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copyEnd = (windowEnd - windowFilled + len) & WindowMask;
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}
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int copied = len;
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int tailLen = len - copyEnd;
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if (tailLen > 0) {
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System.Array.Copy(window, WindowSize - tailLen, output, offset, tailLen);
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offset += tailLen;
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len = copyEnd;
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}
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System.Array.Copy(window, copyEnd - len, output, offset, len);
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windowFilled -= copied;
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if (windowFilled < 0) {
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throw new InvalidOperationException();
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}
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return copied;
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}
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/// <summary>
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/// Reset by clearing window so <see cref="GetAvailable">GetAvailable</see> returns 0
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/// </summary>
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public void Reset()
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{
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windowFilled = windowEnd = 0;
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}
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}
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}
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