Function encoding_mem_is_str_latin1 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn encoding_mem_is_str_latin1(
    buffer: *const u8,
    len: usize,
) -> bool

Checks whether the buffer represents only code points less than or equal to U+00FF.

Fails fast. (I.e. returns before having read the whole buffer if code points above U+00FF are discovered.

Undefined behavior

UB ensues if buffer and buffer_len don’t designate a valid memory block, if buffer is NULL, or if the memory designated by buffer and buffer_len does not contain valid UTF-8. (If buffer_len is 0, buffer may be bogus but still has to be non-NULL.)