Function in3_sys::hdnode_sign_digest

pub unsafe extern "C" fn hdnode_sign_digest(
    node: *mut HDNode, 
    digest: *const u8, 
    sig: *mut u8, 
    pby: *mut u8, 
    is_canonical: Option<unsafe extern "C" fn(by: u8, sig: *mut u8) -> c_int>
) -> c_int