302 lines
11 KiB
C#
302 lines
11 KiB
C#
//
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// © Copyright Henrik Ravn 2004
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//
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// Use, modification and distribution are subject to the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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using System;
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using System.IO;
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using System.Runtime.InteropServices;
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namespace DotZLib
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{
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/// <summary>
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/// Implements a compressed <see cref="Stream"/>, in GZip (.gz) format.
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/// </summary>
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public class GZipStream : Stream, IDisposable
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{
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#region Dll Imports
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl, CharSet=CharSet.Ansi)]
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private static extern IntPtr gzopen(string name, string mode);
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
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private static extern int gzclose(IntPtr gzFile);
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
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private static extern int gzwrite(IntPtr gzFile, int data, int length);
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
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private static extern int gzread(IntPtr gzFile, int data, int length);
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
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private static extern int gzgetc(IntPtr gzFile);
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[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
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private static extern int gzputc(IntPtr gzFile, int c);
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#endregion
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#region Private data
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private IntPtr _gzFile;
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private bool _isDisposed = false;
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private bool _isWriting;
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#endregion
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#region Constructors
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/// <summary>
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/// Creates a new file as a writeable GZipStream
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/// </summary>
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/// <param name="fileName">The name of the compressed file to create</param>
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/// <param name="level">The compression level to use when adding data</param>
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/// <exception cref="ZLibException">If an error occurred in the internal zlib function</exception>
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public GZipStream(string fileName, CompressLevel level)
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{
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_isWriting = true;
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_gzFile = gzopen(fileName, String.Format("wb{0}", (int)level));
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if (_gzFile == IntPtr.Zero)
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throw new ZLibException(-1, "Could not open " + fileName);
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}
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/// <summary>
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/// Opens an existing file as a readable GZipStream
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/// </summary>
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/// <param name="fileName">The name of the file to open</param>
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/// <exception cref="ZLibException">If an error occurred in the internal zlib function</exception>
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public GZipStream(string fileName)
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{
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_isWriting = false;
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_gzFile = gzopen(fileName, "rb");
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if (_gzFile == IntPtr.Zero)
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throw new ZLibException(-1, "Could not open " + fileName);
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}
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#endregion
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#region Access properties
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/// <summary>
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/// Returns true of this stream can be read from, false otherwise
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/// </summary>
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public override bool CanRead
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{
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get
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{
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return !_isWriting;
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}
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}
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/// <summary>
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/// Returns false.
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/// </summary>
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public override bool CanSeek
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{
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get
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{
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return false;
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}
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}
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/// <summary>
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/// Returns true if this tsream is writeable, false otherwise
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/// </summary>
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public override bool CanWrite
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{
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get
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{
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return _isWriting;
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}
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}
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#endregion
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#region Destructor & IDispose stuff
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/// <summary>
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/// Destroys this instance
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/// </summary>
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~GZipStream()
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{
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cleanUp(false);
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}
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/// <summary>
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/// Closes the external file handle
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/// </summary>
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public void Dispose()
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{
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cleanUp(true);
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}
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// Does the actual closing of the file handle.
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private void cleanUp(bool isDisposing)
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{
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if (!_isDisposed)
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{
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gzclose(_gzFile);
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_isDisposed = true;
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}
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}
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#endregion
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#region Basic reading and writing
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/// <summary>
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/// Attempts to read a number of bytes from the stream.
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/// </summary>
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/// <param name="buffer">The destination data buffer</param>
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/// <param name="offset">The index of the first destination byte in <c>buffer</c></param>
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/// <param name="count">The number of bytes requested</param>
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/// <returns>The number of bytes read</returns>
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/// <exception cref="ArgumentNullException">If <c>buffer</c> is null</exception>
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/// <exception cref="ArgumentOutOfRangeException">If <c>count</c> or <c>offset</c> are negative</exception>
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/// <exception cref="ArgumentException">If <c>offset</c> + <c>count</c> is > buffer.Length</exception>
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/// <exception cref="NotSupportedException">If this stream is not readable.</exception>
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/// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
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public override int Read(byte[] buffer, int offset, int count)
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{
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if (!CanRead) throw new NotSupportedException();
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if (buffer == null) throw new ArgumentNullException();
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if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
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if ((offset+count) > buffer.Length) throw new ArgumentException();
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if (_isDisposed) throw new ObjectDisposedException("GZipStream");
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GCHandle h = GCHandle.Alloc(buffer, GCHandleType.Pinned);
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int result;
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try
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{
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result = gzread(_gzFile, h.AddrOfPinnedObject().ToInt32() + offset, count);
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if (result < 0)
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throw new IOException();
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}
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finally
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{
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h.Free();
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}
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return result;
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}
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/// <summary>
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/// Attempts to read a single byte from the stream.
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/// </summary>
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/// <returns>The byte that was read, or -1 in case of error or End-Of-File</returns>
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public override int ReadByte()
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{
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if (!CanRead) throw new NotSupportedException();
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if (_isDisposed) throw new ObjectDisposedException("GZipStream");
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return gzgetc(_gzFile);
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}
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/// <summary>
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/// Writes a number of bytes to the stream
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/// </summary>
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/// <param name="buffer"></param>
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/// <param name="offset"></param>
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/// <param name="count"></param>
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/// <exception cref="ArgumentNullException">If <c>buffer</c> is null</exception>
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/// <exception cref="ArgumentOutOfRangeException">If <c>count</c> or <c>offset</c> are negative</exception>
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/// <exception cref="ArgumentException">If <c>offset</c> + <c>count</c> is > buffer.Length</exception>
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/// <exception cref="NotSupportedException">If this stream is not writeable.</exception>
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/// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
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public override void Write(byte[] buffer, int offset, int count)
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{
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if (!CanWrite) throw new NotSupportedException();
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if (buffer == null) throw new ArgumentNullException();
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if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
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if ((offset+count) > buffer.Length) throw new ArgumentException();
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if (_isDisposed) throw new ObjectDisposedException("GZipStream");
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GCHandle h = GCHandle.Alloc(buffer, GCHandleType.Pinned);
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try
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{
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int result = gzwrite(_gzFile, h.AddrOfPinnedObject().ToInt32() + offset, count);
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if (result < 0)
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throw new IOException();
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}
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finally
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{
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h.Free();
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}
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}
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/// <summary>
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/// Writes a single byte to the stream
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/// </summary>
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/// <param name="value">The byte to add to the stream.</param>
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/// <exception cref="NotSupportedException">If this stream is not writeable.</exception>
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/// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
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public override void WriteByte(byte value)
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{
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if (!CanWrite) throw new NotSupportedException();
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if (_isDisposed) throw new ObjectDisposedException("GZipStream");
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int result = gzputc(_gzFile, (int)value);
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if (result < 0)
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throw new IOException();
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}
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#endregion
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#region Position & length stuff
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/// <summary>
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/// Not supported.
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/// </summary>
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/// <param name="value"></param>
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/// <exception cref="NotSupportedException">Always thrown</exception>
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public override void SetLength(long value)
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{
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throw new NotSupportedException();
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}
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/// <summary>
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/// Not suppported.
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/// </summary>
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/// <param name="offset"></param>
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/// <param name="origin"></param>
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/// <returns></returns>
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/// <exception cref="NotSupportedException">Always thrown</exception>
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public override long Seek(long offset, SeekOrigin origin)
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{
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throw new NotSupportedException();
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}
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/// <summary>
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/// Flushes the <c>GZipStream</c>.
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/// </summary>
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/// <remarks>In this implementation, this method does nothing. This is because excessive
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/// flushing may degrade the achievable compression rates.</remarks>
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public override void Flush()
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{
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// left empty on purpose
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}
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/// <summary>
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/// Gets/sets the current position in the <c>GZipStream</c>. Not suppported.
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/// </summary>
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/// <remarks>In this implementation this property is not supported</remarks>
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/// <exception cref="NotSupportedException">Always thrown</exception>
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public override long Position
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{
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get
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{
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throw new NotSupportedException();
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}
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set
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{
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throw new NotSupportedException();
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}
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}
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/// <summary>
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/// Gets the size of the stream. Not suppported.
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/// </summary>
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/// <remarks>In this implementation this property is not supported</remarks>
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/// <exception cref="NotSupportedException">Always thrown</exception>
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public override long Length
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{
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get
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{
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throw new NotSupportedException();
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}
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}
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#endregion
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}
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}
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