Support the Encoding enumeration in the Encoding Providers

src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Diagnostics;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Runtime.InteropServices;
@@ -290,8 +291,15 @@ public static Encoding GetEncoding(string name,
                 GetEncoding(EncodingTable.GetCodePageFromName(name), encoderFallback, decoderFallback);
         }
 
-        // Return a list of all EncodingInfo objects describing all of our encodings
-        public static EncodingInfo[] GetEncodings() => EncodingTable.GetEncodings();
+        /// <summary>
+        /// Get the <see cref="EncodingInfo"/> list from the runtime and all registered encoding providers
+        /// </summary>
+        /// <returns>The list of the <see cref="EncodingProvider"/> objects</returns>
+        public static EncodingInfo[] GetEncodings()
+        {
+            Dictionary<int, EncodingInfo>? result = EncodingProvider.GetEncodingListFromProviders();
+            return result == null ? EncodingTable.GetEncodings() : EncodingTable.GetEncodings(result);
+        }
 
         public virtual byte[] GetPreamble() => Array.Empty<byte>();
 

src/libraries/System.Private.CoreLib/src/System/Text/EncodingInfo.cs

@@ -6,34 +6,71 @@ namespace System.Text
 {
     public sealed class EncodingInfo
     {
+        /// <summary>
+        /// Construct an <see cref="EncodingInfo"/> object.
+        /// </summary>
+        /// <param name="provider">The <see cref="EncodingProvider"/> object which created this <see cref="EncodingInfo"/> object</param>
+        /// <param name="codePage">The encoding codepage</param>
+        /// <param name="name">The encoding name</param>
+        /// <param name="displayName">The encoding display name</param>
+        /// <returns></returns>
+        public EncodingInfo(EncodingProvider provider, int codePage, string name, string displayName) : this(codePage, name, displayName)
+        {
+            if (name == null || displayName == null || provider == null)
+            {
+                throw new ArgumentNullException(name == null ? nameof(name) : (displayName == null ? nameof(displayName) : nameof(provider)));
+            }
+
+            Provider = provider;
+        }
+
         internal EncodingInfo(int codePage, string name, string displayName)
         {
             CodePage = codePage;
             Name = name;
             DisplayName = displayName;
         }
 
+        /// <summary>
+        /// Get the encoding codepage number
+        /// </summary>
+        /// <value>The codepage integer number</value>
         public int CodePage { get; }
+
+        /// <summary>
+        /// Get the encoding name
+        /// </summary>
+        /// <value>The encoding name string</value>
         public string Name { get; }
+
+        /// <summary>
+        /// Get the encoding display name
+        /// </summary>
+        /// <value>The encoding display name string</value>
         public string DisplayName { get; }
 
-        public Encoding GetEncoding()
-        {
-            return Encoding.GetEncoding(CodePage);
-        }
+        /// <summary>
+        /// Get the <see cref="Encoding"/> object match the information in the <see cref="EncodingInfo"/> object
+        /// </summary>
+        /// <returns>The <see cref="Encoding"/> object</returns>
+        public Encoding GetEncoding() => Provider?.GetEncoding(CodePage) ?? Encoding.GetEncoding(CodePage);
 
-        public override bool Equals(object? value)
-        {
-            if (value is EncodingInfo that)
-            {
-                return this.CodePage == that.CodePage;
-            }
-            return false;
-        }
+        /// <summary>
+        /// Compare this <see cref="EncodingInfo"/> object to other object.
+        /// </summary>
+        /// <param name="value">The other object to compare with this object</param>
+        /// <returns>True if the value object is EncodingInfo object and has a codepage equals to this EncodingInfo object codepage. Otherwise, it returns False</returns>
+        public override bool Equals(object? value) => value is EncodingInfo that && CodePage == that.CodePage;
 
+        /// <summary>
+        /// Get a hashcode representing the current EncodingInfo object.
+        /// </summary>
+        /// <returns>The integer value representing the hash code of the EncodingInfo object.</returns>
         public override int GetHashCode()
         {
             return CodePage;
         }
+
+        internal EncodingProvider? Provider { get; }
     }
 }

src/libraries/System.Private.CoreLib/src/System/Text/EncodingProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections.Generic;
+
 namespace System.Text
 {
     public abstract class EncodingProvider
@@ -37,6 +39,8 @@ public EncodingProvider() { }
             return enc;
         }
 
+        public virtual IEnumerable<EncodingInfo> GetEncodings() => Array.Empty<EncodingInfo>();
+
         internal static void AddProvider(EncodingProvider provider)
         {
             if (provider == null)
@@ -64,10 +68,10 @@ internal static void AddProvider(EncodingProvider provider)
 
         internal static Encoding? GetEncodingFromProvider(int codepage)
         {
-            if (s_providers == null)
+            EncodingProvider[]? providers = s_providers;
+            if (providers == null)
                 return null;
 
-            EncodingProvider[] providers = s_providers;
             foreach (EncodingProvider provider in providers)
             {
                 Encoding? enc = provider.GetEncoding(codepage);
@@ -78,6 +82,29 @@ internal static void AddProvider(EncodingProvider provider)
             return null;
         }
 
+        internal static Dictionary<int, EncodingInfo>? GetEncodingListFromProviders()
+        {
+            EncodingProvider[]? providers = s_providers;
+            if (providers == null)
+                return null;
+
+            Dictionary<int, EncodingInfo> result = new Dictionary<int, EncodingInfo>();
+
+            foreach (EncodingProvider provider in providers)
+            {
+                IEnumerable<EncodingInfo>? encodingInfoList = provider.GetEncodings();
+                if (encodingInfoList != null)
+                {
+                    foreach (EncodingInfo ei in encodingInfoList)
+                    {
+                        result.TryAdd(ei.CodePage, ei);
+                    }
+                }
+            }
+
+            return result;
+        }
+
         internal static Encoding? GetEncodingFromProvider(string encodingName)
         {
             if (s_providers == null)

src/libraries/System.Private.CoreLib/src/System/Text/EncodingTable.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Threading;
 
@@ -105,20 +106,49 @@ private static int InternalGetCodePageFromName(string name)
         // Return a list of all EncodingInfo objects describing all of our encodings
         internal static EncodingInfo[] GetEncodings()
         {
-            EncodingInfo[] arrayEncodingInfo = new EncodingInfo[s_mappedCodePages.Length];
+            ushort[] mappedCodePages = s_mappedCodePages;
+            EncodingInfo[] arrayEncodingInfo = new EncodingInfo[mappedCodePages.Length];
+            string webNames = s_webNames;
+            int[] webNameIndices = s_webNameIndices;
 
-            for (int i = 0; i < s_mappedCodePages.Length; i++)
+            for (int i = 0; i < mappedCodePages.Length; i++)
             {
                 arrayEncodingInfo[i] = new EncodingInfo(
-                    s_mappedCodePages[i],
-                    s_webNames[s_webNameIndices[i]..s_webNameIndices[i + 1]],
-                    GetDisplayName(s_mappedCodePages[i], i)
+                    mappedCodePages[i],
+                    webNames[webNameIndices[i]..webNameIndices[i + 1]],
+                    GetDisplayName(mappedCodePages[i], i)
                     );
             }
 
             return arrayEncodingInfo;
         }
 
+        internal static EncodingInfo[] GetEncodings(Dictionary<int, EncodingInfo> encodingInfoList)
+        {
+            Debug.Assert(encodingInfoList != null);
+            ushort[] mappedCodePages = s_mappedCodePages;
+            string webNames = s_webNames;
+            int[] webNameIndices = s_webNameIndices;
+
+            for (int i = 0; i < mappedCodePages.Length; i++)
+            {
+                if (!encodingInfoList.ContainsKey(mappedCodePages[i]))
+                {
+                    encodingInfoList[mappedCodePages[i]] = new EncodingInfo(mappedCodePages[i], webNames[webNameIndices[i]..webNameIndices[i + 1]],
+                                                                            GetDisplayName(mappedCodePages[i], i));
+                }
+            }
+
+            var result = new EncodingInfo[encodingInfoList.Count];
+            int j = 0;
+            foreach (KeyValuePair<int, EncodingInfo> pair in encodingInfoList)
+            {
+                result[j++] = pair.Value;
+            }
+
+            return result;
+        }
+
         internal static CodePageDataItem? GetCodePageDataItem(int codePage)
         {
             if (s_codePageToCodePageData == null)

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -10262,7 +10262,7 @@ public static void RegisterProvider(System.Text.EncodingProvider provider) { }
     }
     public sealed partial class EncodingInfo
     {
-        internal EncodingInfo() { }
+        public EncodingInfo(System.Text.EncodingProvider provider, int codePage, string name, string displayName) {}
         public int CodePage { get { throw null; } }
         public string DisplayName { get { throw null; } }
         public string Name { get { throw null; } }
@@ -10277,6 +10277,7 @@ public EncodingProvider() { }
         public virtual System.Text.Encoding? GetEncoding(int codepage, System.Text.EncoderFallback encoderFallback, System.Text.DecoderFallback decoderFallback) { throw null; }
         public abstract System.Text.Encoding? GetEncoding(string name);
         public virtual System.Text.Encoding? GetEncoding(string name, System.Text.EncoderFallback encoderFallback, System.Text.DecoderFallback decoderFallback) { throw null; }
+        public virtual System.Collections.Generic.IEnumerable<System.Text.EncodingInfo> GetEncodings() { throw null; }
     }
     public enum NormalizationForm
     {

src/libraries/System.Text.Encoding.CodePages/ref/System.Text.Encoding.CodePages.csproj

@@ -1,9 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Nullable>enable</Nullable>
-    <TargetFrameworks>netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.Text.Encoding.CodePages.cs" />
+    <Compile Include="System.Text.Encoding.CodePages.netcoreapp.cs" Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+    <ProjectReference Include="../../System.Runtime/ref/System.Runtime.csproj" />
   </ItemGroup>
 </Project>

src/libraries/System.Text.Encoding.CodePages/ref/System.Text.Encoding.CodePages.netcoreapp.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Text
+{
+    public sealed partial class CodePagesEncodingProvider : System.Text.EncodingProvider
+    {
+        public override System.Collections.Generic.IEnumerable<System.Text.EncodingInfo> GetEncodings() { throw null; }
+    }
+}

src/libraries/System.Text.Encoding.CodePages/src/System.Text.Encoding.CodePages.csproj

@@ -2,13 +2,13 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <Nullable>enable</Nullable>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Windows_NT;netstandard2.0;netcoreapp2.0-Windows_NT;netstandard2.0-Windows_NT</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Windows_NT;netstandard2.0;netcoreapp2.0-Windows_NT;netstandard2.0-Windows_NT</TargetFrameworks>
     <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <!-- copy the Windows-specific implementation to net461 folder so that restore without a RID works -->
-    <PackageTargetFramework Condition="$(TargetFramework.StartsWith('netstandard')) and '$(TargetsWindows)' == 'true'">netstandard2.0;net461</PackageTargetFramework>    
+    <PackageTargetFramework Condition="$(TargetFramework.StartsWith('netstandard')) and '$(TargetsWindows)' == 'true'">netstandard2.0;net461</PackageTargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Microsoft\Win32\SafeHandles\SafeAllocHHandle.cs" />
@@ -48,6 +48,13 @@
   <ItemGroup Condition="$(TargetFramework.StartsWith('netstandard')) and '$(TargetsWindows)' != 'true' ">
     <Compile Include="System\Text\CodePagesEncodingProvider.Default.cs" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)' and '$(TargetsWindows)' != 'true' ">
+    <Compile Include="System\Text\CodePagesEncodingProvider.Default.cs" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+    <Compile Include="System\Text\CodePagesEncodingProvider.netcoreapp.cs" />
+    <Compile Include="System\Text\BaseCodePageEncoding.netcoreapp.cs" />
+  </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="Data\codepages.nlp">
       <LogicalName>codepages.nlp</LogicalName>

src/libraries/System.Text.Encoding.CodePages/src/System/Text/BaseCodePageEncoding.cs

@@ -41,7 +41,7 @@ namespace System.Text
     //       WORD        byteReplace;    // 2 bytes = 48     // default replacement byte(s)
     //       BYTE[]      data;           // data section
     //   }
-    internal abstract class BaseCodePageEncoding : EncodingNLS, ISerializable
+    internal abstract partial class BaseCodePageEncoding : EncodingNLS, ISerializable
     {
         internal const string CODE_PAGE_DATA_FILE_NAME = "codepages.nlp";
 
@@ -185,6 +185,7 @@ private unsafe void LoadCodePageTables()
             LoadManagedCodePage();
         }
 
+
         // Look up the code page pointer
         private unsafe bool FindCodePage(int codePage)
         {

src/libraries/System.Text.Encoding.CodePages/src/System/Text/BaseCodePageEncoding.netcoreapp.cs

@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Runtime.Serialization;
+using System.Runtime.CompilerServices;
+
+namespace System.Text
+{
+    internal abstract partial class BaseCodePageEncoding : EncodingNLS, ISerializable
+    {
+        internal static unsafe EncodingInfo [] GetEncodings(CodePagesEncodingProvider provider)
+        {
+            lock (s_streamLock)
+            {
+                s_codePagesEncodingDataStream.Seek(CODEPAGE_DATA_FILE_HEADER_SIZE, SeekOrigin.Begin);
+
+                int codePagesCount;
+                fixed (byte* pBytes = &s_codePagesDataHeader[0])
+                {
+                    CodePageDataFileHeader* pDataHeader = (CodePageDataFileHeader*)pBytes;
+                    codePagesCount = pDataHeader->CodePageCount;
+                }
+
+                EncodingInfo [] encodingInfoList = new EncodingInfo[codePagesCount];
+
+                CodePageIndex codePageIndex = default;
+                Span<byte> pCodePageIndex = new Span<byte>(&codePageIndex, Unsafe.SizeOf<CodePageIndex>());
+
+                for (int i = 0; i < codePagesCount; i++)
+                {
+                    s_codePagesEncodingDataStream.Read(pCodePageIndex);
+
+                    string codePageName;
+                    switch (codePageIndex.CodePage)
+                    {
+                        // Fixup some encoding names.
+                        case 950:   codePageName = "big5"; break;
+                        case 10002: codePageName = "x-mac-chinesetrad"; break;
+                        case 20833: codePageName = "x-ebcdic-koreanextended"; break;
+                        default:    codePageName = new string(&codePageIndex.CodePageName); break;
+                    }
+
+                    string? resourceName = EncodingNLS.GetLocalizedEncodingNameResource(codePageIndex.CodePage);
+                    string? displayName = null;
+
+                    if (resourceName != null && resourceName.StartsWith("Globalization_cp_", StringComparison.OrdinalIgnoreCase))
+                    {
+                        displayName = SR.GetResourceString(resourceName);
+                    }
+
+                    encodingInfoList[i] = new EncodingInfo(provider, codePageIndex.CodePage, codePageName, displayName ?? codePageName);
+                }
+
+                return encodingInfoList;
+            }
+        }
+    }
+}