ScopedDemo

gistfile1.txt

Foo("123,456,7890");
Console.WriteLine();
Bar("123,456,7890");

static void Foo(ReadOnlySpan<char> span) {
    Console.WriteLine(span.SplitNext(',').ToString()); // 123
    Console.WriteLine(span.SplitNext(',').ToString()); // 456
    Console.WriteLine(span.SplitNext(',').ToString()); // 7890
}

static void Bar(ReadOnlySpan<char> span) {
    ReadOnlySpan<char> word;
    while (!(word = span.SplitNext(',')).IsEmpty) {
        Console.WriteLine(word.Length);
        Console.WriteLine(word.ToString());
    }
}

public static class Extensions {

    //public static ReadOnlySpan<T> SplitNext<T>(this ref ReadOnlySpan<T> span, T seperator) where T : IEquatable<T> {
    public static ReadOnlySpan<T> SplitNext<T>(this scoped ref ReadOnlySpan<T> span, T seperator) where T : IEquatable<T> {
        int pos = span.IndexOf(seperator);
        if (pos > -1) {
            var part = span.Slice(0, pos);
            span = span.Slice(pos + 1);
            return part;
        } else {
            var part = span;
            span = span.Slice(span.Length);
            return part;
        }
    }

}