Use EncodingForwarder for GetCharCount(byte*, int)

src/mscorlib/src/System/Text/ASCIIEncoding.cs

@@ -155,17 +155,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [System.Runtime.InteropServices.ComVisible(false)]
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)

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

@@ -22,6 +22,14 @@ internal static class EncodingForwarder
         // 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.
+
         public unsafe static int GetByteCount(Encoding encoding, char[] chars, int index, int count)
         {
             // Validate parameters
@@ -205,5 +213,21 @@ public unsafe static int GetCharCount(Encoding encoding, byte[] bytes, int index
             fixed (byte* pBytes = bytes)
                 return encoding.GetCharCount(pBytes + index, count, decoder: null);
         }
+
+        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);
+        }
     }
 }

src/mscorlib/src/System/Text/EncodingNLS.cs

@@ -125,17 +125,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [System.Security.SecurityCritical]  // auto-generated
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }        
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)

src/mscorlib/src/System/Text/UTF32Encoding.cs

@@ -188,17 +188,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [CLSCompliant(false)]
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)

src/mscorlib/src/System/Text/UTF7Encoding.cs

@@ -259,17 +259,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [System.Runtime.InteropServices.ComVisible(false)]
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)

src/mscorlib/src/System/Text/UTF8Encoding.cs

@@ -217,17 +217,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [System.Runtime.InteropServices.ComVisible(false)]
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)

src/mscorlib/src/System/Text/UnicodeEncoding.cs

@@ -189,17 +189,7 @@ public override int GetCharCount(byte[] bytes, int index, int count)
         [System.Runtime.InteropServices.ComVisible(false)]
         public override unsafe int GetCharCount(byte* bytes, int count)
         {
-            // Validate Parameters
-            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 GetCharCount(bytes, count, null);
+            return EncodingForwarder.GetCharCount(this, bytes, count);
         }
 
         // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)