Function byte_offset_of_char

datafusion/functions/src/unicode/common.rs:85–90

(string: &str, n: usize)

/// or `string.len()` if the string has fewer than `n` codepoints.
#[inline]
pub(crate) fn byte_offset_of_char(string: &str, n: usize) -> usize {
    string
        .char_indices()
        .nth(n)
        .map_or(string.len(), |(i, _)| i)
}

/// If `string` has more than `n` codepoints, returns the byte offset of
/// the `n`-th codepoint boundary. Otherwise returns the total codepoint count.