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常用工具集/Utility/ICSharpCode.SharpZipLib/GZip/GzipOutputStream.cs

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+using ICSharpCode.SharpZipLib.Checksum;
+using ICSharpCode.SharpZipLib.Zip.Compression;
+using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
+using System;
+using System.IO;
+using System.Text;
+
+namespace ICSharpCode.SharpZipLib.GZip
+{
+	/// <summary>
+	/// This filter stream is used to compress a stream into a "GZIP" stream.
+	/// The "GZIP" format is described in RFC 1952.
+	///
+	/// author of the original java version : John Leuner
+	/// </summary>
+	/// <example> This sample shows how to gzip a file
+	/// <code>
+	/// using System;
+	/// using System.IO;
+	///
+	/// using ICSharpCode.SharpZipLib.GZip;
+	/// using ICSharpCode.SharpZipLib.Core;
+	///
+	/// class MainClass
+	/// {
+	/// 	public static void Main(string[] args)
+	/// 	{
+	/// 			using (Stream s = new GZipOutputStream(File.Create(args[0] + ".gz")))
+	/// 			using (FileStream fs = File.OpenRead(args[0])) {
+	/// 				byte[] writeData = new byte[4096];
+	/// 				Streamutils.Copy(s, fs, writeData);
+	/// 			}
+	/// 		}
+	/// 	}
+	/// }
+	/// </code>
+	/// </example>
+	public class GZipOutputStream : DeflaterOutputStream
+	{
+		private enum OutputState
+		{
+			Header,
+			Footer,
+			Finished,
+			Closed,
+		};
+
+		#region Instance Fields
+
+		/// <summary>
+		/// CRC-32 value for uncompressed data
+		/// </summary>
+		protected Crc32 crc = new Crc32();
+
+		private OutputState state_ = OutputState.Header;
+
+		private string fileName;
+
+		private GZipFlags flags = 0;
+
+		#endregion Instance Fields
+
+		#region Constructors
+
+		/// <summary>
+		/// Creates a GzipOutputStream with the default buffer size
+		/// </summary>
+		/// <param name="baseOutputStream">
+		/// The stream to read data (to be compressed) from
+		/// </param>
+		public GZipOutputStream(Stream baseOutputStream)
+			: this(baseOutputStream, 4096)
+		{
+		}
+
+		/// <summary>
+		/// Creates a GZipOutputStream with the specified buffer size
+		/// </summary>
+		/// <param name="baseOutputStream">
+		/// The stream to read data (to be compressed) from
+		/// </param>
+		/// <param name="size">
+		/// Size of the buffer to use
+		/// </param>
+		public GZipOutputStream(Stream baseOutputStream, int size) : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size)
+		{
+		}
+
+		#endregion Constructors
+
+		#region Public API
+
+		/// <summary>
+		/// Sets the active compression level (0-9).  The new level will be activated
+		/// immediately.
+		/// </summary>
+		/// <param name="level">The compression level to set.</param>
+		/// <exception cref="ArgumentOutOfRangeException">
+		/// Level specified is not supported.
+		/// </exception>
+		/// <see cref="Deflater"/>
+		public void SetLevel(int level)
+		{
+			if (level < Deflater.NO_COMPRESSION || level > Deflater.BEST_COMPRESSION)
+				throw new ArgumentOutOfRangeException(nameof(level), "Compression level must be 0-9");
+
+			deflater_.SetLevel(level);
+		}
+
+		/// <summary>
+		/// Get the current compression level.
+		/// </summary>
+		/// <returns>The current compression level.</returns>
+		public int GetLevel()
+		{
+			return deflater_.GetLevel();
+		}
+
+		/// <summary>
+		/// Original filename
+		/// </summary>
+		public string FileName
+		{
+			get => fileName;
+			set
+			{
+				fileName = CleanFilename(value);
+				if (string.IsNullOrEmpty(fileName))
+				{
+					flags &= ~GZipFlags.FNAME;
+				}
+				else
+				{
+					flags |= GZipFlags.FNAME;
+				}
+			}
+		}
+
+		#endregion Public API
+
+		#region Stream overrides
+
+		/// <summary>
+		/// Write given buffer to output updating crc
+		/// </summary>
+		/// <param name="buffer">Buffer to write</param>
+		/// <param name="offset">Offset of first byte in buf to write</param>
+		/// <param name="count">Number of bytes to write</param>
+		public override void Write(byte[] buffer, int offset, int count)
+		{
+			if (state_ == OutputState.Header)
+			{
+				WriteHeader();
+			}
+
+			if (state_ != OutputState.Footer)
+			{
+				throw new InvalidOperationException("Write not permitted in current state");
+			}
+
+			crc.Update(new ArraySegment<byte>(buffer, offset, count));
+			base.Write(buffer, offset, count);
+		}
+
+		/// <summary>
+		/// Writes remaining compressed output data to the output stream
+		/// and closes it.
+		/// </summary>
+		protected override void Dispose(bool disposing)
+		{
+			try
+			{
+				Finish();
+			}
+			finally
+			{
+				if (state_ != OutputState.Closed)
+				{
+					state_ = OutputState.Closed;
+					if (IsStreamOwner)
+					{
+						baseOutputStream_.Dispose();
+					}
+				}
+			}
+		}
+
+		/// <summary>
+		/// Flushes the stream by ensuring the header is written, and then calling <see cref="DeflaterOutputStream.Flush">Flush</see>
+		/// on the deflater.
+		/// </summary>
+		public override void Flush()
+		{
+			if (state_ == OutputState.Header)
+			{
+				WriteHeader();
+			}
+
+			base.Flush();
+		}
+
+		#endregion Stream overrides
+
+		#region DeflaterOutputStream overrides
+
+		/// <summary>
+		/// Finish compression and write any footer information required to stream
+		/// </summary>
+		public override void Finish()
+		{
+			// If no data has been written a header should be added.
+			if (state_ == OutputState.Header)
+			{
+				WriteHeader();
+			}
+
+			if (state_ == OutputState.Footer)
+			{
+				state_ = OutputState.Finished;
+				base.Finish();
+
+				var totalin = (uint)(deflater_.TotalIn & 0xffffffff);
+				var crcval = (uint)(crc.Value & 0xffffffff);
+
+				byte[] gzipFooter;
+
+				unchecked
+				{
+					gzipFooter = new byte[] {
+					(byte) crcval, (byte) (crcval >> 8),
+					(byte) (crcval >> 16), (byte) (crcval >> 24),
+
+					(byte) totalin, (byte) (totalin >> 8),
+					(byte) (totalin >> 16), (byte) (totalin >> 24)
+				};
+				}
+
+				baseOutputStream_.Write(gzipFooter, 0, gzipFooter.Length);
+			}
+		}
+
+		#endregion DeflaterOutputStream overrides
+
+		#region Support Routines
+
+		private static string CleanFilename(string path)
+			=> path.Substring(path.LastIndexOf('/') + 1);
+
+		private void WriteHeader()
+		{
+			if (state_ == OutputState.Header)
+			{
+				state_ = OutputState.Footer;
+
+				var mod_time = (int)((DateTime.Now.Ticks - new DateTime(1970, 1, 1).Ticks) / 10000000L);  // Ticks give back 100ns intervals
+				byte[] gzipHeader = {
+					// The two magic bytes
+					GZipConstants.ID1, 
+					GZipConstants.ID2,
+
+					// The compression type
+					GZipConstants.CompressionMethodDeflate,
+
+					// The flags (not set)
+					(byte)flags,
+
+					// The modification time
+					(byte) mod_time, (byte) (mod_time >> 8),
+					(byte) (mod_time >> 16), (byte) (mod_time >> 24),
+
+					// The extra flags
+					0,
+
+					// The OS type (unknown)
+					255
+				};
+
+				baseOutputStream_.Write(gzipHeader, 0, gzipHeader.Length);
+
+				if (flags.HasFlag(GZipFlags.FNAME))
+				{
+					var fname = GZipConstants.Encoding.GetBytes(fileName);
+					baseOutputStream_.Write(fname, 0, fname.Length);
+
+					// End filename string with a \0
+					baseOutputStream_.Write(new byte[] { 0 }, 0, 1);
+				}
+			}
+		}
+
+		#endregion Support Routines
+	}
+}