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常用工具集/Utility/ICSharpCode.SharpZipLib/Tar/TarExtendedHeaderReader.cs

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+using System.Collections.Generic;
+using System.Text;
+
+namespace ICSharpCode.SharpZipLib.Tar
+{
+	/// <summary>
+	/// Reads the extended header of a Tar stream
+	/// </summary>
+	public class TarExtendedHeaderReader
+	{
+		private const byte LENGTH = 0;
+		private const byte KEY = 1;
+		private const byte VALUE = 2;
+		private const byte END = 3;
+
+		private readonly Dictionary<string, string> headers = new Dictionary<string, string>();
+
+		private string[] headerParts = new string[3];
+
+		private int bbIndex;
+		private byte[] byteBuffer;
+		private char[] charBuffer;
+
+		private readonly StringBuilder sb = new StringBuilder();
+		private readonly Decoder decoder = Encoding.UTF8.GetDecoder();
+
+		private int state = LENGTH;
+
+		private static readonly byte[] StateNext = new[] { (byte)' ', (byte)'=', (byte)'\n' };
+
+		/// <summary>
+		/// Creates a new <see cref="TarExtendedHeaderReader"/>.
+		/// </summary>
+		public TarExtendedHeaderReader()
+		{
+			ResetBuffers();
+		}
+
+		/// <summary>
+		/// Read <paramref name="length"/> bytes from <paramref name="buffer"/>
+		/// </summary>
+		/// <param name="buffer"></param>
+		/// <param name="length"></param>
+		public void Read(byte[] buffer, int length)
+		{
+			for (int i = 0; i < length; i++)
+			{
+				byte next = buffer[i];
+
+				if (next == StateNext[state])
+				{
+					Flush();
+					headerParts[state] = sb.ToString();
+					sb.Clear();
+
+					if (++state == END)
+					{
+						headers.Add(headerParts[KEY], headerParts[VALUE]);
+						headerParts = new string[3];
+						state = LENGTH;
+					}
+				}
+				else
+				{
+					byteBuffer[bbIndex++] = next;
+					if (bbIndex == 4)
+						Flush();
+				}
+			}
+		}
+
+		private void Flush()
+		{
+			decoder.Convert(byteBuffer, 0, bbIndex, charBuffer, 0, 4, false, out int bytesUsed, out int charsUsed, out bool completed);
+
+			sb.Append(charBuffer, 0, charsUsed);
+			ResetBuffers();
+		}
+
+		private void ResetBuffers()
+		{
+			charBuffer = new char[4];
+			byteBuffer = new byte[4];
+			bbIndex = 0;
+		}
+
+		/// <summary>
+		/// Returns the parsed headers as key-value strings
+		/// </summary>
+		public Dictionary<string, string> Headers
+		{
+			get
+			{
+				// TODO: Check for invalid state? -NM 2018-07-01
+				return headers;
+			}
+		}
+	}
+}