/// <summary>
/// Reports the zero-based index of the first occurrence of the specified <paramref name="value"/> in the current <paramref name="span"/>.
/// <param name="span">The source span.</param>
/// <param name="value">The value to seek within the source span.</param>
/// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="value"/> are compared.</param>
/// </summary>
public static int IndexOf(this ReadOnlySpan <char> span, ReadOnlySpan <char> value, StringComparison comparisonType)
{
string.CheckStringComparison(comparisonType);
if (comparisonType == StringComparison.Ordinal)
{
return(SpanHelpers.IndexOf(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(value), value.Length));
}
switch (comparisonType)
{
case StringComparison.CurrentCulture:
case StringComparison.CurrentCultureIgnoreCase:
return(CultureInfo.CurrentCulture.CompareInfo.IndexOf(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType)));
case StringComparison.InvariantCulture:
case StringComparison.InvariantCultureIgnoreCase:
return(CompareInfo.Invariant.IndexOf(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType)));
default:
Debug.Assert(comparisonType == StringComparison.OrdinalIgnoreCase);
return(Ordinal.IndexOfOrdinalIgnoreCase(span, value));
}
}