.ISAE
                    ALU
                    BPDIGEST

;; Proof-of-work mining
;;
;; # Arguments
;; - s16[1]: input
;; - a256[1]: difficulty target
;; - a16[2]: limit to the number of mining cycles
;;
;; # Returns
;; - st0: success code (0 for success, 1 for a failure)
;; - r256[2]: resulting hash value
;; - a16[1]: actual number of cycles used
;;
;; # Uses
;; - a8[1]: temporary result code
;; - a16[3]: zero
.ROUTINE mine
                    put  0, a16[1]              ; putting a value into register
                    put  0, a16[3]              ; we will use this later
loop:                                           ; label for cycle
                    sha2 s16[1], r256[2]        ; taking hash of the data
                    inj  s16[1], r256[2], a16[3] ; changing the string with the hash itself
                    inc  a16[1]                 ; counting steps
                    gt.u a16[1], a16[2]         ; making sure we do not exceed $cycle_limit
                    jif  exceeded
                    lt.u r256[2], r256[1]       ; checking against difficulty
                    jif  done                   ; target difficulty reached!
                    jmp  loop
done:               put  1, a8[1]               ; failing since we exceeded $cycle_limit
                    ifz  a8[1]
                    ret
exceeded:           put  0, a8[1]
                    st.s a8[1]
                    ret