Function secp256k1_sys::secp256k1_ecdh

pub unsafe extern "C" fn secp256k1_ecdh(
    cx: *const Context, 
    output: *mut c_uchar, 
    pubkey: *const PublicKey, 
    privkey: *const c_uchar, 
    hashfp: EcdhHashFn, 
    data: *mut c_void
) -> c_int