Spanified Webencoders.Base64UrlEncode (#11047)

Author: gfoidl

src/Http/WebUtilities/ref/Microsoft.AspNetCore.WebUtilities.netcoreapp3.0.cs

@@ -233,6 +233,7 @@ public static partial class WebEncoders
         public static string Base64UrlEncode(byte[] input) { throw null; }
         public static int Base64UrlEncode(byte[] input, int offset, char[] output, int outputOffset, int count) { throw null; }
         public static string Base64UrlEncode(byte[] input, int offset, int count) { throw null; }
+        public static string Base64UrlEncode(System.ReadOnlySpan<byte> input) { throw null; }
         public static int GetArraySizeRequiredToDecode(int count) { throw null; }
         public static int GetArraySizeRequiredToEncode(int count) { throw null; }
     }

src/Shared/WebEncoders/WebEncoders.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Buffers;
 using System.Diagnostics;
 using System.Globalization;
 using Microsoft.Extensions.WebEncoders.Sources;
@@ -220,6 +221,9 @@ public static string Base64UrlEncode(byte[] input, int offset, int count)
 
             ValidateParameters(input.Length, nameof(input), offset, count);
 
+#if NETCOREAPP3_0
+            return Base64UrlEncode(input.AsSpan(offset, count));
+#else
             // Special-case empty input
             if (count == 0)
             {
@@ -229,7 +233,8 @@ public static string Base64UrlEncode(byte[] input, int offset, int count)
             var buffer = new char[GetArraySizeRequiredToEncode(count)];
             var numBase64Chars = Base64UrlEncode(input, offset, buffer, outputOffset: 0, count: count);
 
-            return new String(buffer, startIndex: 0, length: numBase64Chars);
+            return new string(buffer, startIndex: 0, length: numBase64Chars);
+#endif
         }
 
         /// <summary>
@@ -280,6 +285,9 @@ public static int Base64UrlEncode(byte[] input, int offset, char[] output, int o
                     nameof(count));
             }
 
+#if NETCOREAPP3_0
+            return Base64UrlEncode(input.AsSpan(offset, count), output.AsSpan(outputOffset));
+#else
             // Special-case empty input.
             if (count == 0)
             {
@@ -311,6 +319,7 @@ public static int Base64UrlEncode(byte[] input, int offset, char[] output, int o
             }
 
             return numBase64Chars;
+#endif
         }
 
         /// <summary>
@@ -327,6 +336,73 @@ public static int GetArraySizeRequiredToEncode(int count)
             return checked(numWholeOrPartialInputBlocks * 4);
         }
 
+#if NETCOREAPP3_0
+        /// <summary>
+        /// Encodes <paramref name="input"/> using base64url encoding.
+        /// </summary>
+        /// <param name="input">The binary input to encode.</param>
+        /// <returns>The base64url-encoded form of <paramref name="input"/>.</returns>
+        public static string Base64UrlEncode(ReadOnlySpan<byte> input)
+        {
+            if (input.IsEmpty)
+            {
+                return string.Empty;
+            }
+
+            int bufferSize = GetArraySizeRequiredToEncode(input.Length);
+
+            char[] bufferToReturnToPool = null;
+            Span<char> buffer = bufferSize <= 128
+                ? stackalloc char[bufferSize]
+                : bufferToReturnToPool = ArrayPool<char>.Shared.Rent(bufferSize);
+
+            var numBase64Chars = Base64UrlEncode(input, buffer);
+            var base64Url = new string(buffer.Slice(0, numBase64Chars));
+
+            if (bufferToReturnToPool != null)
+            {
+                ArrayPool<char>.Shared.Return(bufferToReturnToPool);
+            }
+
+            return base64Url;
+        }
+
+        private static int Base64UrlEncode(ReadOnlySpan<byte> input, Span<char> output)
+        {
+            Debug.Assert(output.Length >= GetArraySizeRequiredToEncode(input.Length));
+
+            if (input.IsEmpty)
+            {
+                return 0;
+            }
+
+            // Use base64url encoding with no padding characters. See RFC 4648, Sec. 5.
+
+            Convert.TryToBase64Chars(input, output, out int charsWritten);
+
+            // Fix up '+' -> '-' and '/' -> '_'. Drop padding characters.
+            for (var i = 0; i < charsWritten; i++)
+            {
+                var ch = output[i];
+                if (ch == '+')
+                {
+                    output[i] = '-';
+                }
+                else if (ch == '/')
+                {
+                    output[i] = '_';
+                }
+                else if (ch == '=')
+                {
+                    // We've reached a padding character; truncate the remainder.
+                    return i;
+                }
+            }
+
+            return charsWritten;
+        }
+#endif
+
         private static int GetNumBase64PaddingCharsInString(string str)
         {
             // Assumption: input contains a well-formed base64 string with no whitespace.

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionManager.cs

@@ -105,11 +105,10 @@ public void RemoveConnection(string id)
 
         private static string MakeNewConnectionId()
         {
-            // TODO: Use Span when WebEncoders implements Span methods https://github.com/aspnet/Home/issues/2966
             // 128 bit buffer / 8 bits per byte = 16 bytes
-            var buffer = new byte[16];
-            _keyGenerator.GetBytes(buffer);
+            Span<byte> buffer = stackalloc byte[16];
             // Generate the id with RNGCrypto because we want a cryptographically random id, which GUID is not
+            _keyGenerator.GetBytes(buffer);
             return WebEncoders.Base64UrlEncode(buffer);
         }