func wbase(b BigInt) *C.uint8_t {
	if len(b) == 0 {
		return nil
	}
	return (*C.uint8_t)(unsafe.Pointer(&b[0]))
}

const wordBytes = bits.UintSize / 8

func bigToBN(x BigInt) *C.GO_BIGNUM {
	return C._goboringcrypto_BN_le2bn(wbase(x), C.size_t(len(x)*wordBytes), nil)
}

func bytesToBN(x []byte) *C.GO_BIGNUM {
	return C._goboringcrypto_BN_bin2bn((*C.uint8_t)(&x[0]), C.size_t(len(x)), nil)
}

func bnToBig(bn *C.GO_BIGNUM) BigInt {

unsigned _goboringcrypto_BN_num_bytes(const GO_BIGNUM*);
int _goboringcrypto_BN_is_negative(const GO_BIGNUM*);
GO_BIGNUM* _goboringcrypto_BN_bin2bn(const uint8_t*, size_t, GO_BIGNUM*);
GO_BIGNUM* _goboringcrypto_BN_le2bn(const uint8_t*, size_t, GO_BIGNUM*);
size_t _goboringcrypto_BN_bn2bin(const GO_BIGNUM*, uint8_t*);
int _goboringcrypto_BN_bn2le_padded(uint8_t*, size_t, const GO_BIGNUM*);