feat(zip): better string encoding handling (#592)

This replaces the global static ZipStrings singleton with instances of StringCodec, which will:

- Remove encoding configuration from a shared global state
- Allow for different defaults for input and output
- Explicitly override the encodings used for ZipCrypto and zip archive comments (the one in the Central Directory, not the individual entry comments).
- Use "Unicode" for new entries (unless overriden)
- Make it much more clear (hopefully) how and why different encodings are used.

src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/DeflaterOutputStream.cs

@@ -2,6 +2,7 @@
 using System;
 using System.IO;
 using System.Security.Cryptography;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -203,6 +204,9 @@ public bool CanPatchEntries
 		/// </summary>
 		protected byte[] AESAuthCode;
 
+		/// <inheritdoc cref="StringCodec.ZipCryptoEncoding"/>
+		public Encoding ZipCryptoEncoding { get; set; } = StringCodec.DefaultZipCryptoEncoding;
+
 		/// <summary>
 		/// Encrypt a block of data
 		/// </summary>

src/ICSharpCode.SharpZipLib/Zip/FastZip.cs

@@ -345,6 +345,29 @@ public Deflater.CompressionLevel CompressionLevel
 			set { compressionLevel_ = value; }
 		}
 
+		/// <summary>
+		/// Reflects the opposite of the internal <see cref="StringCodec.ForceZipLegacyEncoding"/>, setting it to <c>false</c> overrides the encoding used for reading and writing zip entries
+		/// </summary>
+		public bool UseUnicode
+		{
+			get => !_stringCodec.ForceZipLegacyEncoding;
+			set => _stringCodec.ForceZipLegacyEncoding = !value;
+		}
+
+		/// <summary> Gets or sets the code page used for reading/writing zip file entries when unicode is disabled </summary>
+		public int LegacyCodePage
+		{
+			get => _stringCodec.CodePage;
+			set => _stringCodec.CodePage = value;
+		}
+
+		/// <inheritdoc cref="StringCodec"/>
+		public StringCodec StringCodec
+		{
+			get => _stringCodec;
+			set => _stringCodec = value;
+		}
+
 		#endregion Properties
 
 		#region Delegates
@@ -456,7 +479,7 @@ private void CreateZip(Stream outputStream, string sourceDirectory, bool recurse
 			NameTransform = new ZipNameTransform(sourceDirectory);
 			sourceDirectory_ = sourceDirectory;
 
-			using (outputStream_ = new ZipOutputStream(outputStream))
+			using (outputStream_ = new ZipOutputStream(outputStream, _stringCodec))
 			{
 				outputStream_.SetLevel((int)CompressionLevel);
 				outputStream_.IsStreamOwner = !leaveOpen;
@@ -631,6 +654,10 @@ private void ProcessFile(object sender, ScanEventArgs e)
 					using (FileStream stream = File.Open(e.Name, FileMode.Open, FileAccess.Read, FileShare.Read))
 					{
 						ZipEntry entry = entryFactory_.MakeFileEntry(e.Name);
+						if (_stringCodec.ForceZipLegacyEncoding)
+						{
+							entry.IsUnicodeText = false;
+						}
 
 						// Set up AES encryption for the entry if required.
 						ConfigureEntryEncryption(entry);
@@ -967,6 +994,7 @@ private static bool NameIsValid(string name)
 		private INameTransform extractNameTransform_;
 		private UseZip64 useZip64_ = UseZip64.Dynamic;
 		private CompressionLevel compressionLevel_ = CompressionLevel.DEFAULT_COMPRESSION;
+		private StringCodec _stringCodec = new StringCodec();
 
 		private string password_;
 

src/ICSharpCode.SharpZipLib/Zip/ZipConstants.cs

@@ -471,48 +471,5 @@ public static class ZipConstants
 		public const int ENDSIG = 'P' | ('K' << 8) | (5 << 16) | (6 << 24);
 
 		#endregion Header Signatures
-
-		/// <summary>
-		/// Default encoding used for string conversion.  0 gives the default system OEM code page.
-		/// Using the default code page isnt the full solution necessarily
-		/// there are many variable factors, codepage 850 is often a good choice for
-		/// European users, however be careful about compatability.
-		/// </summary>
-		[Obsolete("Use ZipStrings instead")]
-		public static int DefaultCodePage
-		{
-			get => ZipStrings.CodePage;
-			set => ZipStrings.CodePage = value;
-		}
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToString(byte[], int)"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToString instead")]
-		public static string ConvertToString(byte[] data, int count)
-			=> ZipStrings.ConvertToString(data, count);
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToString(byte[])"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToString instead")]
-		public static string ConvertToString(byte[] data)
-			=> ZipStrings.ConvertToString(data);
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToStringExt(int, byte[], int)"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToStringExt instead")]
-		public static string ConvertToStringExt(int flags, byte[] data, int count)
-			=> ZipStrings.ConvertToStringExt(flags, data, count);
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToStringExt(int, byte[])"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToStringExt instead")]
-		public static string ConvertToStringExt(int flags, byte[] data)
-			=> ZipStrings.ConvertToStringExt(flags, data);
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToArray(string)"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToArray instead")]
-		public static byte[] ConvertToArray(string str)
-			=> ZipStrings.ConvertToArray(str);
-
-		/// <summary> Deprecated wrapper for <see cref="ZipStrings.ConvertToArray(int, string)"/></summary>
-		[Obsolete("Use ZipStrings.ConvertToArray instead")]
-		public static byte[] ConvertToArray(int flags, string str)
-			=> ZipStrings.ConvertToArray(flags, str);
 	}
 }

src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Text;
 
 namespace ICSharpCode.SharpZipLib.Zip
 {
@@ -150,7 +151,7 @@ private enum Known : byte
 		/// The name passed is null
 		/// </exception>
 		public ZipEntry(string name)
-			: this(name, 0, ZipConstants.VersionMadeBy, CompressionMethod.Deflated)
+			: this(name, 0, ZipConstants.VersionMadeBy, CompressionMethod.Deflated, true)
 		{
 		}
 
@@ -171,7 +172,7 @@ public ZipEntry(string name)
 		/// </exception>
 		internal ZipEntry(string name, int versionRequiredToExtract)
 			: this(name, versionRequiredToExtract, ZipConstants.VersionMadeBy,
-			CompressionMethod.Deflated)
+			CompressionMethod.Deflated, true)
 		{
 		}
 
@@ -182,6 +183,7 @@ internal ZipEntry(string name, int versionRequiredToExtract)
 		/// <param name="madeByInfo">Version and HostSystem Information</param>
 		/// <param name="versionRequiredToExtract">Minimum required zip feature version required to extract this entry</param>
 		/// <param name="method">Compression method for this entry.</param>
+		/// <param name="unicode">Whether the entry uses unicode for name and comment</param>
 		/// <exception cref="ArgumentNullException">
 		/// The name passed is null
 		/// </exception>
@@ -193,7 +195,7 @@ internal ZipEntry(string name, int versionRequiredToExtract)
 		/// It is not generally useful, use the constructor specifying the name only.
 		/// </remarks>
 		internal ZipEntry(string name, int versionRequiredToExtract, int madeByInfo,
-			CompressionMethod method)
+			CompressionMethod method, bool unicode)
 		{
 			if (name == null)
 			{
@@ -216,7 +218,7 @@ internal ZipEntry(string name, int versionRequiredToExtract)
 			this.versionToExtract = (ushort)versionRequiredToExtract;
 			this.method = method;
 
-			IsUnicodeText = ZipStrings.UseUnicode;
+			IsUnicodeText = unicode;
 		}
 
 		/// <summary>

src/ICSharpCode.SharpZipLib/Zip/ZipEntryFactory.cs

@@ -68,7 +68,7 @@ public enum TimeSetting
 		public ZipEntryFactory()
 		{
 			nameTransform_ = new ZipNameTransform();
-			isUnicodeText_ = ZipStrings.UseUnicode;
+			isUnicodeText_ = true;
 		}
 
 		/// <summary>
@@ -162,7 +162,7 @@ public int SetAttributes
 		}
 
 		/// <summary>
-		/// Get set a value indicating whether unidoce text should be set on.
+		/// Get set a value indicating whether unicode text should be set on.
 		/// </summary>
 		public bool IsUnicodeText
 		{