Function utf8proc_iterate 

pub unsafe extern "C" fn utf8proc_iterate(
    str_: *const utf8proc_uint8_t,
    strlen: utf8proc_ssize_t,
    codepoint_ref: *mut utf8proc_int32_t,
) -> utf8proc_ssize_t

Reads a single codepoint from the UTF-8 sequence being pointed to by str. The maximum number of bytes read is strlen, unless strlen is negative (in which case up to 4 bytes are read).

If a valid codepoint could be read, it is stored in the variable pointed to by codepoint_ref, otherwise that variable will be set to -1. In case of success, the number of bytes read is returned; otherwise, a negative error code is returned.