Refactor UriHelper.cs to use a static lambda and UriComponents struct

This commit includes a significant refactor of the `UriHelper.cs` file. Unused namespaces `System.Buffers` and `System.Runtime.CompilerServices` have been removed. The `InitializeAbsoluteUriStringSpanAction` delegate and `InitializeAbsoluteUriString` method, as well as the `CopyTextToBuffer` method, have been removed.

A new struct `UriComponents` has been introduced to encapsulate the components of a URI: `Scheme`, `Host`, `PathBase`, `Path`, `Query`, and `Fragment`. The `string.Create` method call has been updated to use a new lambda function that leverages the `UriComponents` struct to copy each component of the URI into the buffer, adjusting the buffer slice as needed. This function also handles the case where both `PathBase` and `Path` components have a slash, removing the trailing slash from `PathBase` to avoid duplication.

Finally, the `BuildAbsolute` method has been updated to use the new `UriComponents` struct and the updated `string.Create` call.

src/Http/Http.Extensions/src/UriHelper.cs

@@ -1,9 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Buffers;
 using System.Diagnostics.CodeAnalysis;
-using System.Runtime.CompilerServices;
 using System.Text;
 
 namespace Microsoft.AspNetCore.Http.Extensions;
@@ -17,7 +15,6 @@ public static class UriHelper
     private const char Hash = '#';
     private const char QuestionMark = '?';
     private static readonly string SchemeDelimiter = Uri.SchemeDelimiter;
-    private static readonly SpanAction<char, (string scheme, string host, string pathBase, string path, string query, string fragment)> InitializeAbsoluteUriStringSpanAction = new(InitializeAbsoluteUriString);
 
     /// <summary>
     /// Combines the given URI components into a string that is properly encoded for use in HTTP headers.
@@ -90,7 +87,41 @@ public static string BuildAbsolute(
             length--;
         }
 
-        return string.Create(length, (scheme, hostText, pathBaseText, pathText, queryText, fragmentText), InitializeAbsoluteUriStringSpanAction);
+        return string.Create(
+            length,
+            new UriComponents(scheme, hostText, pathBaseText, pathText, queryText, fragmentText),
+            static (buffer, uriComponents) =>
+            {
+                uriComponents.Scheme.AsSpan().CopyTo(buffer);
+                buffer = buffer.Slice(uriComponents.Scheme.Length);
+
+                Uri.SchemeDelimiter.CopyTo(buffer);
+                buffer = buffer.Slice(Uri.SchemeDelimiter.Length);
+
+                uriComponents.Host.AsSpan().CopyTo(buffer);
+                buffer = buffer.Slice(uriComponents.Host.Length);
+
+                var pathBaseSpan = uriComponents.PathBase.AsSpan();
+
+                if (uriComponents.Path.Length > 0 && pathBaseSpan.Length > 0 && pathBaseSpan[^1] == '/')
+                {
+                    // If the path string has a trailing slash and the other string has a leading slash, we need
+                    // to trim one of them.
+                    // Trim the last slash from pathBase. The total length was decremented before the call to string.Create.
+                    pathBaseSpan = pathBaseSpan[..^1];
+                }
+
+                pathBaseSpan.CopyTo(buffer);
+                buffer = buffer.Slice(pathBaseSpan.Length);
+
+                uriComponents.Path.CopyTo(buffer);
+                buffer = buffer.Slice(uriComponents.Path.Length);
+
+                uriComponents.Query.CopyTo(buffer);
+                buffer = buffer.Slice(uriComponents.Query.Length);
+
+                uriComponents.Fragment.CopyTo(buffer);
+            });
     }
 
     /// <summary>
@@ -224,45 +255,23 @@ public static string GetDisplayUrl(this HttpRequest request)
             .ToString();
     }
 
-    /// <summary>
-    /// Copies the specified <paramref name="text"/> to the specified <paramref name="buffer"/> starting at the specified <paramref name="index"/>.
-    /// </summary>
-    /// <param name="buffer">The buffer to copy text to.</param>
-    /// <param name="index">The buffer start index.</param>
-    /// <param name="text">The text to copy.</param>
-    /// <returns></returns>
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static int CopyTextToBuffer(Span<char> buffer, int index, ReadOnlySpan<char> text)
-    {
-        text.CopyTo(buffer.Slice(index, text.Length));
-        return index + text.Length;
-    }
-
-    /// <summary>
-    /// Initializes the URI <see cref="string"/> for <see cref="BuildAbsolute(string, HostString, PathString, PathString, QueryString, FragmentString)"/>.
-    /// </summary>
-    /// <param name="buffer">The URI <see cref="string"/>'s <see cref="char"/> buffer.</param>
-    /// <param name="uriParts">The URI parts.</param>
-    private static void InitializeAbsoluteUriString(Span<char> buffer, (string scheme, string host, string pathBase, string path, string query, string fragment) uriParts)
+    private readonly struct UriComponents
     {
-        var index = 0;
-
-        var pathBaseSpan = uriParts.pathBase.AsSpan();
+        public readonly string Scheme;
+        public readonly string Host;
+        public readonly string PathBase;
+        public readonly string Path;
+        public readonly string Query;
+        public readonly string Fragment;
 
-        if (uriParts.path.Length > 0 && pathBaseSpan.Length > 0 && pathBaseSpan[^1] == '/')
+        public UriComponents(string scheme, string host, string pathBase, string path, string query, string fragment)
         {
-            // If the path string has a trailing slash and the other string has a leading slash, we need
-            // to trim one of them.
-            // Trim the last slahs from pathBase. The total length was decremented before the call to string.Create.
-            pathBaseSpan = pathBaseSpan[..^1];
+            Scheme = scheme;
+            Host = host;
+            PathBase = pathBase;
+            Path = path;
+            Query = query;
+            Fragment = fragment;
         }
-
-        index = CopyTextToBuffer(buffer, index, uriParts.scheme.AsSpan());
-        index = CopyTextToBuffer(buffer, index, Uri.SchemeDelimiter.AsSpan());
-        index = CopyTextToBuffer(buffer, index, uriParts.host.AsSpan());
-        index = CopyTextToBuffer(buffer, index, pathBaseSpan);
-        index = CopyTextToBuffer(buffer, index, uriParts.path.AsSpan());
-        index = CopyTextToBuffer(buffer, index, uriParts.query.AsSpan());
-        _ = CopyTextToBuffer(buffer, index, uriParts.fragment.AsSpan());
     }
 }