Function pem_write_buffer 

pub unsafe extern "C" fn pem_write_buffer(
    header: *const c_char,
    footer: *const c_char,
    der_data: *const c_uchar,
    der_len: usize,
    buf: *mut c_uchar,
    buf_len: usize,
    olen: *mut usize,
) -> c_int