_wp_utf8_codepoint_span()

_wp_utf8_codepoint_span( string $text, int $byte_offset, int $max_code_points, ?int $found_code_points ): int

function _wp_utf8_codepoint_span( string $text, int $byte_offset, int $max_code_points, ?int &$found_code_points = 0 ): int {
	$was_at            = $byte_offset;
	$invalid_length    = 0;
	$end               = strlen( $text );
	$found_code_points = 0;

	while ( $byte_offset < $end && $found_code_points < $max_code_points ) {
		$needed      = $max_code_points - $found_code_points;
		$chunk_count = _wp_scan_utf8( $text, $byte_offset, $invalid_length, null, $needed );

		$found_code_points += $chunk_count;

		// Invalid spans only convey one code point count regardless of how long they are.
		if ( 0 !== $invalid_length && $found_code_points < $max_code_points ) {
			++$found_code_points;
			$byte_offset += $invalid_length;
		}
	}

	return $byte_offset - $was_at;
}