How to convert the data type for ccall

[1112]

Всем привет!
Как преобразовать тип для ccall?
Вот код на C

typedef  struct {
    unsigned  char data [ 64 ];
} my_pubkey;

that’s what I was trying to do on Julia

struct pubkey
    Cuchar::NTuple{64, Int}
end

private_key = 7

pub = ccall((:secp256k1_ec_pubkey_create, "/usr/local/lib/libsecp256k1.so"), Int, (Pair{Int64, Int64}, Ref{pubkey}, Int32), secp256k1_ctx, pubkey, private_key)