Revert "Revert EncodingForwarder"

src/mscorlib/mscorlib.shared.sources.props

@@ -991,6 +991,7 @@
     <TextSources Include="$(BclSourcesRoot)\System\Text\EncoderFallback.cs" />
     <TextSources Include="$(BclSourcesRoot)\System\Text\EncoderReplacementFallback.cs" />
     <TextSources Include="$(BclSourcesRoot)\System\Text\Encoding.cs" />
+    <TextSources Include="$(BclSourcesRoot)\System\Text\EncodingForwarder.cs" />
     <TextSources Include="$(BclSourcesRoot)\System\Text\EncodingInfo.cs" />
     <TextSources Include="$(BclSourcesRoot)\System\Text\EncodingNLS.cs" />
     <TextSources Include="$(BclSourcesRoot)\System\Text\EncodingProvider.cs" />

src/mscorlib/src/System/Text/EncodingForwarder.cs

@@ -0,0 +1,339 @@
+// 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.Diagnostics.Contracts;
+using System.Security;
+
+namespace System.Text
+{
+    // Shared implementations for commonly overriden Encoding methods
+
+    internal static class EncodingForwarder
+    {
+        // We normally have to duplicate a lot of code between UTF8Encoding,
+        // UTF7Encoding, EncodingNLS, etc. because we want to override many
+        // of the methods in all of those classes to just forward to the unsafe
+        // version. (e.g. GetBytes(char[]))
+        // Ideally, everything would just derive from EncodingNLS, but that's
+        // not exposed in the public API, and C# prohibits a public class from
+        // inheriting from an internal one. So, we have to override each of the
+        // methods in question and repeat the argument validation/logic.
+
+        // These set of methods exist so instead of duplicating code, we can
+        // simply have those overriden methods call here to do the actual work.
+
+        // NOTE: This class should ONLY be called from Encodings that override
+        // the internal methods which accept an Encoder/DecoderNLS. The reason
+        // for this is that by default, those methods just call the same overload
+        // except without the encoder/decoder parameter. If an overriden method
+        // without that parameter calls this class, which calls the overload with
+        // the parameter, it will call the same method again, which will eventually
+        // lead to a StackOverflowException.
+
+        [SecuritySafeCritical]
+        public unsafe static int GetByteCount(Encoding encoding, char[] chars, int index, int count)
+        {
+            // Validate parameters
+
+            Contract.Assert(encoding != null); // this parameter should only be affected internally, so just do a debug check here
+            if (chars == null)
+            {
+                throw new ArgumentNullException("chars", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? "index" : "count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (chars.Length - index < count)
+            {
+                throw new ArgumentOutOfRangeException("chars", Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
+            }
+            Contract.EndContractBlock();
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the (internal) pointer version
+            fixed (char* pChars = chars)
+                return encoding.GetByteCount(pChars + index, count, encoder: null);
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static int GetByteCount(Encoding encoding, string s)
+        {
+            Contract.Assert(encoding != null);
+            if (s == null)
+            {
+                string paramName = encoding is ASCIIEncoding ? "chars" : "s"; // ASCIIEncoding calls the string chars
+                // UTF8Encoding does this as well, but it originally threw an ArgumentNull for "s" so don't check for that
+                throw new ArgumentNullException(paramName);
+            }
+            Contract.EndContractBlock();
+
+            // NOTE: The behavior of fixed *is* defined by
+            // the spec for empty strings, although not for
+            // null strings/empty char arrays. See
+            // http://stackoverflow.com/q/37757751/4077294
+            // Regardless, we may still want to check
+            // for if (s.Length == 0) in the future
+            // and short-circuit as an optimization (TODO).
+
+            fixed (char* pChars = s)
+                return encoding.GetByteCount(pChars, s.Length, encoder: null);
+        }
+
+        [SecurityCritical]
+        public unsafe static int GetByteCount(Encoding encoding, char* chars, int count)
+        {
+            Contract.Assert(encoding != null);
+            if (chars == null)
+            {
+                throw new ArgumentNullException("chars", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            Contract.EndContractBlock();
+
+            // Call the internal version, with an empty encoder
+            return encoding.GetByteCount(chars, count, encoder: null);
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static int GetBytes(Encoding encoding, string s, int charIndex, int charCount, byte[] bytes, int byteIndex)
+        {
+            Contract.Assert(encoding != null);
+            if (s == null || bytes == null)
+            {
+                string stringName = encoding is ASCIIEncoding ? "chars" : "s"; // ASCIIEncoding calls the first parameter chars
+                throw new ArgumentNullException(s == null ? stringName : "bytes", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (charIndex < 0 || charCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(charIndex < 0 ? "charIndex" : "charCount", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (s.Length - charIndex < charCount)
+            {
+                string stringName = encoding is ASCIIEncoding ? "chars" : "s"; // ASCIIEncoding calls the first parameter chars
+                // Duplicate the above check since we don't want the overhead of a type check on the general path
+                throw new ArgumentOutOfRangeException(stringName, Environment.GetResourceString("ArgumentOutOfRange_IndexCount"));
+            }
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+            {
+                throw new ArgumentOutOfRangeException("byteIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
+            }
+            Contract.EndContractBlock();
+
+            int byteCount = bytes.Length - byteIndex;
+
+            // Fixed doesn't like empty arrays
+            if (bytes.Length == 0)
+                bytes = new byte[1];
+
+            fixed (char* pChars = s) fixed (byte* pBytes = bytes)
+            {
+                return encoding.GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, encoder: null);
+            }
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static int GetBytes(Encoding encoding, char[] chars, int charIndex, int charCount, byte[] bytes, int byteIndex)
+        {
+            Contract.Assert(encoding != null);
+            if (chars == null || bytes == null)
+            {
+                throw new ArgumentNullException(chars == null ? "chars" : "bytes", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (charIndex < 0 || charCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(charIndex < 0 ? "charIndex" : "charCount", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (chars.Length - charIndex < charCount)
+            {
+                throw new ArgumentOutOfRangeException("chars", Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
+            }
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+            {
+                throw new ArgumentOutOfRangeException("byteIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
+            }
+            Contract.EndContractBlock();
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Note that this is the # of bytes to decode,
+            // not the size of the array
+            int byteCount = bytes.Length - byteIndex;
+
+            // Fixed doesn't like 0 length arrays.
+            if (bytes.Length == 0)
+                bytes = new byte[1];
+
+            // Just call the (internal) pointer version
+            fixed (char* pChars = chars) fixed (byte* pBytes = bytes)
+            {
+                return encoding.GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, encoder: null);
+            }
+        }
+
+        [SecurityCritical]
+        public unsafe static int GetBytes(Encoding encoding, char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null || chars == null)
+            {
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (charCount < 0 || byteCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(charCount < 0 ? "charCount" : "byteCount", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            Contract.EndContractBlock();
+
+            return encoding.GetBytes(chars, charCount, bytes, byteCount, encoder: null);
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static int GetCharCount(Encoding encoding, byte[] bytes, int index, int count)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null)
+            {
+                throw new ArgumentNullException("bytes", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? "index" : "count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (bytes.Length - index < count)
+            {
+                throw new ArgumentOutOfRangeException("bytes", Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
+            }
+            Contract.EndContractBlock();
+
+            // If no input just return 0, fixed doesn't like 0 length arrays.
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return encoding.GetCharCount(pBytes + index, count, decoder: null);
+        }
+
+        [SecurityCritical]
+        public unsafe static int GetCharCount(Encoding encoding, byte* bytes, int count)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null)
+            {
+                throw new ArgumentNullException("bytes", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            Contract.EndContractBlock();
+
+            return encoding.GetCharCount(bytes, count, decoder: null);
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static int GetChars(Encoding encoding, byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null || chars == null)
+            {
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (byteIndex < 0 || byteCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(byteIndex < 0 ? "byteIndex" : "byteCount", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (bytes.Length - byteIndex < byteCount)
+            {
+                throw new ArgumentOutOfRangeException("bytes", Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
+            }
+            if (charIndex < 0 || charIndex > chars.Length)
+            {
+                throw new ArgumentOutOfRangeException("charIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
+            }
+            Contract.EndContractBlock();
+
+            if (byteCount == 0)
+                return 0;
+
+            // NOTE: This is the # of chars we can decode,
+            // not the size of the array
+            int charCount = chars.Length - charIndex;
+
+            // Fixed doesn't like 0 length arrays.
+            if (chars.Length == 0)
+                chars = new char[1];
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = chars)
+            {
+                return encoding.GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, decoder: null);
+            }
+        }
+
+        [SecurityCritical]
+        public unsafe static int GetChars(Encoding encoding, byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null || chars == null)
+            {
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (charCount < 0 || byteCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(charCount < 0 ? "charCount" : "byteCount", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            Contract.EndContractBlock();
+
+            return encoding.GetChars(bytes, byteCount, chars, charCount, decoder: null);
+        }
+
+        [SecuritySafeCritical]
+        public unsafe static string GetString(Encoding encoding, byte[] bytes, int index, int count)
+        {
+            Contract.Assert(encoding != null);
+            if (bytes == null)
+            {
+                throw new ArgumentNullException("bytes", Environment.GetResourceString("ArgumentNull_Array"));
+            }
+            if (index < 0 || count < 0)
+            {
+                // ASCIIEncoding has different names for its parameters here (byteIndex, byteCount)
+                bool ascii = encoding is ASCIIEncoding;
+                string indexName = ascii ? "byteIndex" : "index";
+                string countName = ascii ? "byteCount" : "count";
+                throw new ArgumentOutOfRangeException(index < 0 ? indexName : countName, Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
+            }
+            if (bytes.Length - index < count)
+            {
+                throw new ArgumentOutOfRangeException("bytes", Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
+            }
+            Contract.EndContractBlock();
+
+            // Avoid problems with empty input buffer
+            if (count == 0)
+                return string.Empty;
+
+            // Call string.CreateStringFromEncoding here, which
+            // allocates a string and lets the Encoding modify
+            // it in place. This way, we don't have to allocate
+            // an intermediary char[] to decode into and then
+            // call the string constructor; instead we decode
+            // directly into the string.
+
+            fixed (byte* pBytes = bytes)
+            {
+                return string.CreateStringFromEncoding(pBytes + index, count, encoding);
+            }
+        }
+    }
+}