255 lines
11 KiB
C#
255 lines
11 KiB
C#
#region Disclaimer / License
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// Copyright (C) 2008, Kenneth Skovhede
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// http://www.hexad.dk, opensource@hexad.dk
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library 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 GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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//
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#endregion
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using System;
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using System.Collections.Generic;
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using System.Text;
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namespace Duplicati.SharpRSync
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{
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/// <summary>
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/// This class contains operations on a RDiff compatible delta file
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/// </summary>
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public class DeltaFile
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{
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ChecksumFile m_checksum;
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System.IO.Stream m_inputStream;
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/// <summary>
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/// Constructs a new DeltaFile based on a signature file.
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/// This instance can be used to create a new DeltaFile
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/// </summary>
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/// <param name="checksum">The checksum to use</param>
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public DeltaFile(ChecksumFile checksum)
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{
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m_checksum = checksum;
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}
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/// <summary>
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/// Constructs a new DeltaFile by reading the stream.
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/// This instance can be used to patch a file.
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/// </summary>
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/// <param name="inputStream">The stream containing the delta information</param>
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public DeltaFile(System.IO.Stream inputStream)
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{
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m_inputStream = inputStream;
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}
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/// <summary>
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/// Creates a new file based on the basefile and the delta information.
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/// The basefile and output stream cannot point to the same resource (ea. file).
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/// The base file MUST be seekable.
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/// </summary>
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/// <param name="basefile">A seekable stream with the baseinformation</param>
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/// <param name="output">The stream to write the patched data to. Must not point to the same resource as the basefile.</param>
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public void PatchFile(System.IO.Stream basefile, System.IO.Stream output)
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{
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byte[] sig = new byte[4];
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if (Utility.ForceStreamRead(m_inputStream, sig, 4) != 4)
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throw new Exception("End of stream occured while reading initial 4 bytes of delta file");
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for (int i = 0; i < sig.Length; i++)
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if (RDiffBinary.DELTA_MAGIC[i] != sig[i])
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throw new Exception("Delta stream did not have the correct start marker");
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//Keep reading until we hit the end command
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while (true)
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{
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int command = m_inputStream.ReadByte();
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if (command == RDiffBinary.EndCommand)
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break;
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//It is an error to omit the end command
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if (command < 0)
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throw new Exception("Stream ended but had no end marker");
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if (Enum.IsDefined(typeof(RDiffBinary.LiteralDeltaCommand), command))
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{
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//Find out how many bytes of literal data there is
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int len = RDiffBinary.GetLiteralLength((RDiffBinary.LiteralDeltaCommand)command);
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byte[] tmp = new byte[len];
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if (Utility.ForceStreamRead(m_inputStream, tmp, tmp.Length) != tmp.Length)
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throw new Exception("Unexpected end of stream detected");
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long size = RDiffBinary.DecodeLength(tmp);
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if (size < 0)
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throw new Exception("Invalid size for literal data");
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//Copy the literal data from the patch to the output
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Utility.StreamCopy(m_inputStream, output, size);
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}
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else if (Enum.IsDefined(typeof(RDiffBinary.CopyDeltaCommand), command))
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{
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//Find the offset of the data in the base file
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int len = RDiffBinary.GetCopyOffsetSize((RDiffBinary.CopyDeltaCommand)command);
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byte[] tmp = new byte[len];
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if (Utility.ForceStreamRead(m_inputStream, tmp, tmp.Length) != tmp.Length)
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throw new Exception("Unexpected end of stream detected");
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long offset = RDiffBinary.DecodeLength(tmp);
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if (offset < 0)
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throw new Exception("Invalid offset for copy data");
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//Find the length of the data to copy from the basefile
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len = RDiffBinary.GetCopyLengthSize((RDiffBinary.CopyDeltaCommand)command);
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tmp = new byte[len];
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if (Utility.ForceStreamRead(m_inputStream, tmp, tmp.Length) != tmp.Length)
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throw new Exception("Unexpected end of stream detected");
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long length = RDiffBinary.DecodeLength(tmp);
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if (length < 0)
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throw new Exception("Invalid length for copy data");
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//Seek to the begining, and copy
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basefile.Position = offset;
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Utility.StreamCopy(basefile, output, length);
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}
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else if (command <= RDiffBinary.LiteralLimit)
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{
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//Literal data less than 64 bytes are found, copy it
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Utility.StreamCopy(m_inputStream, output, command);
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}
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else
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throw new Exception("Unknown command in delta file");
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}
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output.Flush();
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}
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/// <summary>
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/// Generates a delta file from input, and writes it to output
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/// </summary>
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/// <param name="input">The stream to generate the delta from</param>
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/// <param name="output">The stream to write the delta to</param>
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public void GenerateDeltaFile(System.IO.Stream input, System.IO.Stream output)
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{
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RollingBuffer buffer = new RollingBuffer(input);
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output.Write(RDiffBinary.DELTA_MAGIC, 0, RDiffBinary.DELTA_MAGIC.Length);
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Adler32Checksum adler = new Adler32Checksum(buffer, m_checksum.BlockLength);
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System.Security.Cryptography.HashAlgorithm md4 = System.Security.Cryptography.MD4.Create("MD4");
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md4.Initialize();
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byte[] md4buffer = new byte[m_checksum.BlockLength];
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int unmatched = 0;
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do
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{
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List<KeyValuePair<int, byte[]>> strong = m_checksum.FindChunk(adler.Checksum);
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//No weak matches :(
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if (strong != null && strong.Count == 0)
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unmatched++;
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else
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{
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//A weak match, check for MD4 matches
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byte[] tmp;
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if (buffer.Count < m_checksum.BlockLength)
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tmp = buffer.GetHead(buffer.Count);
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else
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{
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buffer.GetHead(md4buffer, 0, md4buffer.Length);
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tmp = md4buffer;
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}
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foreach (KeyValuePair<int, byte[]> k in strong)
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{
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if (!md4.CanReuseTransform)
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md4 = System.Security.Cryptography.MD4.Create("MD4");
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md4.Initialize();
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tmp = md4.ComputeHash(tmp);
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bool matches = true;
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for(int i = 0; i < m_checksum.StrongLength; i++)
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if (tmp[i] != k.Value[i])
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{
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matches = false;
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break;
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}
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if (matches)
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{
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//Send leading bytes as a literal block
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if (unmatched > 0)
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{
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WriteLiteral(buffer.GetTail(unmatched), output);
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unmatched = 0;
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}
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//Send the matching bytes as a copy
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WriteCopy(k.Key * m_checksum.BlockLength, m_checksum.BlockLength, output);
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adler.Reset();
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buffer.DropTail(buffer.Count);
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break;
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}
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}
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//Avoid keeping too large blocks in memory.
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//This gives an overhead of app. 3 bytes pr. 2Kb data
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if (unmatched > m_checksum.BlockLength)
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{
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WriteLiteral(buffer.GetTail(unmatched), output);
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buffer.DropTail(unmatched);
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unmatched = 0;
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adler.Reset();
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}
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}
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} while (adler.AdvanceChecksum());
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//Any trailing bytes are treated as a literal
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if (unmatched > 0)
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{
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WriteLiteral(buffer.GetTail(unmatched), output);
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buffer.DropTail(unmatched);
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unmatched = 0;
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adler.Reset();
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}
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output.WriteByte((byte)RDiffBinary.EndCommand);
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output.Flush();
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}
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/// <summary>
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/// Writes a literal command to a delta stream
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/// </summary>
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/// <param name="data">The literal data to write</param>
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/// <param name="output">The output delta stream</param>
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private void WriteLiteral(byte[] data, System.IO.Stream output)
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{
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output.WriteByte((byte)RDiffBinary.FindLiteralDeltaCommand(data.Length));
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byte[] len = RDiffBinary.EncodeLength(data.Length);
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output.Write(len, 0, len.Length);
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output.Write(data, 0, data.Length);
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}
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/// <summary>
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/// Write a copy command to a delta stream
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/// </summary>
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/// <param name="offset">The offset in the basefile where the data is located</param>
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/// <param name="length">The length of the data to copy</param>
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/// <param name="output">The output delta stream</param>
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private void WriteCopy(long offset, int length, System.IO.Stream output)
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{
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output.WriteByte((byte)RDiffBinary.FindCopyDeltaCommand(offset, length));
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byte[] len = RDiffBinary.EncodeLength(offset);
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output.Write(len, 0, len.Length);
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len = RDiffBinary.EncodeLength(length);
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output.Write(len, 0, len.Length);
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}
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}
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}
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