pub unsafe extern "C" fn ecdsa_write_signature( ctx: *mut ecdsa_context, md_alg: md_type_t, hash: *const c_uchar, hlen: size_t, sig: *mut c_uchar, slen: *mut size_t, f_rng: Option<unsafe extern "C" fn(arg1: *mut c_void, arg2: *mut c_uchar, arg3: size_t) -> c_int>, p_rng: *mut c_void) -> c_int