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Removed bound checks in SharedUrlHelper.IsLocalUrl and use JIT unrolling for checks #61361

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Removed bound checks in SharedUrlHelper.IsLocalUrl and use JIT unrolling for checks #61361

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f33bc03
Removed bound checks in SharedUrlHelper.IsLocalUrl and use JIT unroll…
gfoidl Apr 7, 2025
baa3cd9
Optimized the case '/'
gfoidl Apr 7, 2025
75dd59e
Force inline of the HasControlCharacter as it's an easy loop
gfoidl Apr 7, 2025
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24 changes: 13 additions & 11 deletions src/Shared/ResultsHelpers/SharedUrlHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
using System;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using Microsoft.AspNetCore.Http;

namespace Microsoft.AspNetCore.Internal;
Expand Down Expand Up @@ -32,49 +33,50 @@ internal static class SharedUrlHelper

internal static bool IsLocalUrl([NotNullWhen(true)] string? url)
{
if (string.IsNullOrEmpty(url))
var urlSpan = url.AsSpan();

if (urlSpan.IsEmpty)
{
return false;
}

// Allows "/" or "/foo" but not "//" or "/\".
if (url[0] == '/')
if (urlSpan[0] == '/')
{
// url is exactly "/"
if (url.Length == 1)
if (urlSpan.Length < 2)
{
return true;
}

// url doesn't start with "//" or "/\"
if (url[1] != '/' && url[1] != '\\')
if (urlSpan[1] is not '/' and '\\')
{
return !HasControlCharacter(url.AsSpan(1));
return !HasControlCharacter(urlSpan.Slice(1));
}

return false;
}

// Allows "~/" or "~/foo" but not "~//" or "~/\".
if (url[0] == '~' && url.Length > 1 && url[1] == '/')
if (urlSpan.StartsWith("~/"))
{
// url is exactly "~/"
if (url.Length == 2)
if (urlSpan.Length < 3)
{
return true;
}

// url doesn't start with "~//" or "~/\"
if (url[2] != '/' && url[2] != '\\')
if (urlSpan[2] is not '/' and '\\')
{
return !HasControlCharacter(url.AsSpan(2));
return !HasControlCharacter(urlSpan.Slice(2));
}

return false;
}

return false;

[MethodImpl(MethodImplOptions.AggressiveInlining)]
static bool HasControlCharacter(ReadOnlySpan<char> readOnlySpan)
{
// URLs may not contain ASCII control characters.
Expand Down
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