/// <summary>
/// Determines whether the beginning of the <paramref name="span"/> matches the specified <paramref name="value"/> when compared using the specified <paramref name="comparisonType"/> option.
/// </summary>
/// <param name="span">The source span.</param>
/// <param name="value">The sequence to compare to the beginning of 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>
public static bool StartsWith(this ReadOnlySpan <char> span, ReadOnlySpan <char> value, StringComparison comparisonType)
{
if (value.Length == 0)
{
string.CheckStringComparison(comparisonType);
return(true);
}
switch (comparisonType)
{
case StringComparison.CurrentCulture:
return(SpanHelpers.StartsWithCultureHelper(span, value, CultureInfo.CurrentCulture.CompareInfo));
case StringComparison.CurrentCultureIgnoreCase:
return(SpanHelpers.StartsWithCultureIgnoreCaseHelper(span, value, CultureInfo.CurrentCulture.CompareInfo));
case StringComparison.InvariantCulture:
return(SpanHelpers.StartsWithCultureHelper(span, value, CompareInfo.Invariant));
case StringComparison.InvariantCultureIgnoreCase:
return(SpanHelpers.StartsWithCultureIgnoreCaseHelper(span, value, CompareInfo.Invariant));
case StringComparison.Ordinal:
return(span.StartsWith(value)); //TODO: Optimize - https://github.com/dotnet/corefx/issues/27487
case StringComparison.OrdinalIgnoreCase:
return(SpanHelpers.StartsWithOrdinalIgnoreCaseHelper(span, value));
default:
throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
}
}