ctx2        C.GO_HMAC_CTX
	size        int
	blockSize   int
	key         []byte
	sum         []byte
	needCleanup bool
}

func (h *boringHMAC) Reset() {
	if h.needCleanup {
		C._goboringcrypto_HMAC_CTX_cleanup(&h.ctx)
	} else {
		h.needCleanup = true
		// Note: Because of the finalizer, any time h.ctx is passed to cgo,
		// that call must be followed by a call to runtime.KeepAlive(h),

size_t _goboringcrypto_EVP_MD_size(const GO_EVP_MD*);

// #include <openssl/hmac.h>
typedef struct GO_HMAC_CTX { char data[104]; } GO_HMAC_CTX;
void _goboringcrypto_HMAC_CTX_init(GO_HMAC_CTX*);
void _goboringcrypto_HMAC_CTX_cleanup(GO_HMAC_CTX*);
int _goboringcrypto_HMAC_Init(GO_HMAC_CTX*, const void*, int, const GO_EVP_MD*);
int _goboringcrypto_HMAC_Update(GO_HMAC_CTX*, const uint8_t*, size_t);