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Optimize new use of Base64Url #57050

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Merged
merged 2 commits into from
Jul 31, 2024
Merged

Optimize new use of Base64Url #57050

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01fcf76
Optimize new use of Base64Url
stephentoub Jul 29, 2024
b81bd50
Clarify comment
amcasey Jul 31, 2024
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17 changes: 13 additions & 4 deletions src/Shared/WebEncoders/WebEncoders.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,11 @@ namespace Microsoft.Extensions.Internal;
#endif
static class WebEncoders
{
#if NET9_0_OR_GREATER
/// <summary>SearchValues for the two Base64 and two Base64Url chars that differ from each other.</summary>
private static readonly SearchValues<char> s_base64vsBase64UrlDifferentiators = SearchValues.Create("+/-_");
#endif

/// <summary>
/// Decodes a base64url-encoded string.
/// </summary>
Expand Down Expand Up @@ -69,9 +74,11 @@ public static byte[] Base64UrlDecode(string input, int offset, int count)

#if NET9_0_OR_GREATER
// Legacy behavior of Base64UrlDecode supports either Base64 or Base64Url input.
// If it doesn't have + or /, it can be treated as Base64Url.
// If it has a - or _, or if it doesn't have + or /, it can be treated as Base64Url.
// Searching for any of them allows us to stop the search as early as we know whether Base64Url should be used.
ReadOnlySpan<char> inputSpan = input.AsSpan(offset, count);
if (!inputSpan.ContainsAny('+', '/'))
int indexOfFirstDifferentiator = inputSpan.IndexOfAny(s_base64vsBase64UrlDifferentiators);
if (indexOfFirstDifferentiator < 0 || inputSpan[indexOfFirstDifferentiator] is '-' or '_')
{
return Base64Url.DecodeFromChars(inputSpan);
}
Expand Down Expand Up @@ -124,9 +131,11 @@ public static byte[] Base64UrlDecode(string input, int offset, char[] buffer, in

#if NET9_0_OR_GREATER
// Legacy behavior of Base64UrlDecode supports either Base64 or Base64Url input.
// If it doesn't have + or /, it can be treated as Base64Url.
// If it has a - or _, or if it doesn't have + or /, it can be treated as Base64Url.
// Searching for any of them allows us to stop the search as early as we know Base64Url should be used.
ReadOnlySpan<char> inputSpan = input.AsSpan(offset, count);
if (!inputSpan.ContainsAny('+', '/'))
int indexOfFirstDifferentiator = inputSpan.IndexOfAny(s_base64vsBase64UrlDifferentiators);
if (indexOfFirstDifferentiator < 0 || inputSpan[indexOfFirstDifferentiator] is '-' or '_')
{
return Base64Url.DecodeFromChars(inputSpan);
}
Expand Down