HttpDateParser.cs

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using System.Globalization;
 
namespace System.Net;
 
internal static class HttpDateParser
{
    private static readonly string[] s_dateFormats = new string[21]
    {
        "ddd, d MMM yyyy H:m:s 'GMT'", "ddd, d MMM yyyy H:m:s 'UTC'", "ddd, d MMM yyyy H:m:s", "d MMM yyyy H:m:s 'GMT'", "d MMM yyyy H:m:s 'UTC'", "d MMM yyyy H:m:s", "ddd, d MMM yy H:m:s 'GMT'", "ddd, d MMM yy H:m:s 'UTC'", "ddd, d MMM yy H:m:s", "d MMM yy H:m:s 'GMT'",
        "d MMM yy H:m:s 'UTC'", "d MMM yy H:m:s", "dddd, d'-'MMM'-'yy H:m:s 'GMT'", "dddd, d'-'MMM'-'yy H:m:s 'UTC'", "dddd, d'-'MMM'-'yy H:m:s zzz", "dddd, d'-'MMM'-'yy H:m:s", "ddd MMM d H:m:s yyyy", "ddd, d MMM yyyy H:m:s zzz", "ddd, d MMM yyyy H:m:s", "d MMM yyyy H:m:s zzz",
        "d MMM yyyy H:m:s"
    };
 
    internal static bool TryParse(ReadOnlySpan<char> input, out DateTimeOffset result)
    {
        input = input.Trim();
        if (!DateTimeOffset.TryParseExact(input, "r", DateTimeFormatInfo.InvariantInfo, DateTimeStyles.None, out result))
        {
            return DateTimeOffset.TryParseExact(input, s_dateFormats, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AllowInnerWhite | DateTimeStyles.AssumeUniversal, out result);
        }
        return true;
    }
 
    internal static string DateToString(DateTimeOffset dateTime)
    {
        return dateTime.ToUniversalTime().ToString("r");
    }
}