typedef struct _sha256_ctx {
	uint8_t data[64];		/**< holds sha-256 block for transformation */
	uint8_t datalen;		/**< holds the current length of data in data[64] */
	uint8_t bitlen[8];		/**< holds the current length of transformed data */
	uint32_t state[8];		/**< holds hash state for transformed data */
} sha256_ctx;

typedef struct _hash_ctx {
    uint24_t fn_init;
    uint24_t fn_update;
    uint24_t fn_final;
    union _hash {
        sha256_ctx sha256;
    };
} hash_ctx;