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常用工具集/Utility/ICSharpCode.SharpZipLib/Zip/ZipStrings.cs

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+using System;
+using System.Text;
+using ICSharpCode.SharpZipLib.Core;
+
+namespace ICSharpCode.SharpZipLib.Zip
+{
+	/// <summary>
+	/// This static class contains functions for encoding and decoding zip file strings
+	/// </summary>
+	public static class ZipStrings
+	{
+		static ZipStrings()
+		{
+			try
+			{
+				var platformCodepage = Encoding.GetEncoding(0).CodePage;
+				SystemDefaultCodePage = (platformCodepage == 1 || platformCodepage == 2 || platformCodepage == 3 || platformCodepage == 42) ? FallbackCodePage : platformCodepage;
+			}
+			catch
+			{
+				SystemDefaultCodePage = FallbackCodePage;
+			}
+		}
+
+		/// <summary>Code page backing field</summary>
+		/// <remarks>
+		/// The original Zip specification (https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT) states
+		/// that file names should only be encoded with IBM Code Page 437 or UTF-8.
+		/// In practice, most zip apps use OEM or system encoding (typically cp437 on Windows).
+		/// Let's be good citizens and default to UTF-8 http://utf8everywhere.org/
+		/// </remarks>
+		private static int codePage = AutomaticCodePage;
+
+		/// Automatically select codepage while opening archive
+		/// see https://github.com/icsharpcode/SharpZipLib/pull/280#issuecomment-433608324
+		/// 
+		private const int AutomaticCodePage = -1;
+
+		/// <summary>
+		/// Encoding used for string conversion. Setting this to 65001 (UTF-8) will
+		/// also set the Language encoding flag to indicate UTF-8 encoded file names.
+		/// </summary>
+		public static int CodePage
+		{
+			get
+			{
+				return codePage == AutomaticCodePage? Encoding.UTF8.CodePage:codePage;
+			}
+			set
+			{
+				if ((value < 0) || (value > 65535) ||
+					(value == 1) || (value == 2) || (value == 3) || (value == 42))
+				{
+					throw new ArgumentOutOfRangeException(nameof(value));
+				}
+
+				codePage = value;
+			}
+		}
+
+		private const int FallbackCodePage = 437;
+
+		/// <summary>
+		/// Attempt to get the operating system default codepage, or failing that, to
+		/// the fallback code page IBM 437.
+		/// </summary>
+		public static int SystemDefaultCodePage { get; }
+
+		/// <summary>
+		/// Get whether the default codepage is set to UTF-8. Setting this property to false will
+		/// set the <see cref="CodePage"/> to <see cref="SystemDefaultCodePage"/>
+		/// </summary>
+		/// <remarks>
+		/// Get OEM codepage from NetFX, which parses the NLP file with culture info table etc etc.
+		/// But sometimes it yields the special value of 1 which is nicknamed <c>CodePageNoOEM</c> in <see cref="Encoding"/> sources (might also mean <c>CP_OEMCP</c>, but Encoding puts it so).
+		/// This was observed on Ukranian and Hindu systems.
+		/// Given this value, <see cref="Encoding.GetEncoding(int)"/> throws an <see cref="ArgumentException"/>.
+		/// So replace it with <see cref="FallbackCodePage"/>, (IBM 437 which is the default code page in a default Windows installation console.
+		/// </remarks>
+		public static bool UseUnicode
+		{
+			get
+			{
+				return codePage == Encoding.UTF8.CodePage;
+			}
+			set
+			{
+				if (value)
+				{
+					codePage = Encoding.UTF8.CodePage;
+				}
+				else
+				{
+					codePage = SystemDefaultCodePage;
+				}
+			}
+		}
+
+		/// <summary>
+		/// Convert a portion of a byte array to a string using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="data">
+		/// Data to convert to string
+		/// </param>
+		/// <param name="count">
+		/// Number of bytes to convert starting from index 0
+		/// </param>
+		/// <returns>
+		/// data[0]..data[count - 1] converted to a string
+		/// </returns>
+		public static string ConvertToString(byte[] data, int count)
+			=> data == null
+			? string.Empty
+			: Encoding.GetEncoding(CodePage).GetString(data, 0, count);
+
+		/// <summary>
+		/// Convert a byte array to a string using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="data">
+		/// Byte array to convert
+		/// </param>
+		/// <returns>
+		/// <paramref name="data">data</paramref>converted to a string
+		/// </returns>
+		public static string ConvertToString(byte[] data)
+			=> ConvertToString(data, data.Length);
+
+		private static Encoding EncodingFromFlag(int flags)
+			=> ((flags & (int)GeneralBitFlags.UnicodeText) != 0)
+				? Encoding.UTF8
+				: Encoding.GetEncoding(
+					// if CodePage wasn't set manually and no utf flag present
+					// then we must use SystemDefault (old behavior)
+					// otherwise, CodePage should be preferred over SystemDefault
+					// see https://github.com/icsharpcode/SharpZipLib/issues/274
+					codePage == AutomaticCodePage? 
+						SystemDefaultCodePage:
+						codePage);
+
+		/// <summary>
+		/// Convert a byte array to a string  using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="flags">The applicable general purpose bits flags</param>
+		/// <param name="data">
+		/// Byte array to convert
+		/// </param>
+		/// <param name="count">The number of bytes to convert.</param>
+		/// <returns>
+		/// <paramref name="data">data</paramref>converted to a string
+		/// </returns>
+		public static string ConvertToStringExt(int flags, byte[] data, int count)
+			=> (data == null)
+				? string.Empty
+				: EncodingFromFlag(flags).GetString(data, 0, count);
+
+		/// <summary>
+		/// Convert a byte array to a string using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="data">
+		/// Byte array to convert
+		/// </param>
+		/// <param name="flags">The applicable general purpose bits flags</param>
+		/// <returns>
+		/// <paramref name="data">data</paramref>converted to a string
+		/// </returns>
+		public static string ConvertToStringExt(int flags, byte[] data)
+			=> ConvertToStringExt(flags, data, data.Length);
+
+		/// <summary>
+		/// Convert a string to a byte array using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="str">
+		/// String to convert to an array
+		/// </param>
+		/// <returns>Converted array</returns>
+		public static byte[] ConvertToArray(string str)
+			=> str == null
+			? Empty.Array<byte>()
+			: Encoding.GetEncoding(CodePage).GetBytes(str);
+
+		/// <summary>
+		/// Convert a string to a byte array using <see cref="CodePage"/>
+		/// </summary>
+		/// <param name="flags">The applicable <see cref="GeneralBitFlags">general purpose bits flags</see></param>
+		/// <param name="str">
+		/// String to convert to an array
+		/// </param>
+		/// <returns>Converted array</returns>
+		public static byte[] ConvertToArray(int flags, string str)
+			=> (string.IsNullOrEmpty(str))
+				? Empty.Array<byte>()
+				: EncodingFromFlag(flags).GetBytes(str);
+	}
+}