Fift and TVM assembly

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Key differences

• Built-in words, constants, and variables:
  5 dup * // 25 at the top of the stack
  
• TVM instruction bitcode definitions, like in Asm.fif:
  // Tuple primitives
  x{6F0} @Defop(4u) TUPLE
  x{6F00} @Defop NIL
  x{6F01} @Defop SINGLE
  x{6F02} dup @Defop PAIR @Defop CONS
  
• Intertwined macros and TVM opcodes, like in wallet_v3_r2.fif:
  "Asm.fif" include
  <{ SETCP0 DUP IFNOTRET // Return if recv_internal
     DUP 85143 INT EQUAL OVER 78748 INT EQUAL OR IFJMP:<{ // "seqno" and "get_public_key" get-methods
       1 INT AND c4 PUSHCTR CTOS 32 LDU 32 LDU NIP 256 PLDU CONDSEL  // cnt or pubk
     }>
     INC 32 THROWIF    // Fail unless recv_external
     9 PUSHPOW2 LDSLICEX DUP 32 LDU 32 LDU 32 LDU     // signature in_msg subwallet_id valid_until msg_seqno cs
     NOW s1 s3 XCHG LEQ 35 THROWIF    // signature in_msg subwallet_id cs msg_seqno
     c4 PUSH CTOS 32 LDU 32 LDU 256 LDU ENDS    // signature in_msg subwallet_id cs msg_seqno stored_seqno stored_subwallet public_key
     s3 s2 XCPU EQUAL 33 THROWIFNOT    // signature in_msg subwallet_id cs public_key stored_seqno stored_subwallet
     s4 s4 XCPU EQUAL 34 THROWIFNOT    // signature in_msg stored_subwallet cs public_key stored_seqno
     s0 s4 XCHG HASHSU    // signature stored_seqno stored_subwallet cs public_key msg_hash
     s0 s5 s5 XC2PU    // public_key stored_seqno stored_subwallet cs msg_hash signature public_key
     CHKSIGNU 35 THROWIFNOT    // public_key stored_seqno stored_subwallet cs
     ACCEPT
     WHILE:<{
       DUP SREFS    // public_key stored_seqno stored_subwallet cs _51
     }>DO<{    // public_key stored_seqno stored_subwallet cs
       8 LDU LDREF s0 s2 XCHG    // public_key stored_seqno stored_subwallet cs _56 mode
       SENDRAWMSG
     }>    // public_key stored_seqno stored_subwallet cs
     ENDS SWAP INC    // public_key stored_subwallet seqno'
     NEWC 32 STU 32 STU 256 STU ENDC c4 POP
  }>c
  

​

Smart contract usage

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(Fift) Including large BoCs in contracts

1. Editing project.yaml to include fift/blob.fif:
   contract:
     fift:
       - fift/blob.fif
     func:
       - func/code.fc
   
2. Adding the BoC to fift/blob.boc
3. Including this code in fift/blob.fif:
   <b 8 4 u, 8 4 u, "fift/blob.boc" file>B B>boc ref, b> <s @Defop LDBLOB
   

cell load_blob() asm "LDBLOB";

() recv_internal() {
    send_raw_message(load_blob(), 160);
}

​

(TVM assembly) Converting integers to strings

tuple digitize_number(int value)
  asm "NIL WHILE:<{ OVER }>DO<{ SWAP TEN DIVMOD s1 s2 XCHG TPUSH }> NIP";

builder store_number(builder msg, tuple t)
  asm "WHILE:<{ DUP TLEN }>DO<{ TPOP 48 ADDCONST ROT 8 STU SWAP }> DROP";

builder store_signed(builder msg, int v) inline_ref {
  if (v < 0) {
    return msg.store_uint(45, 8).store_number(digitize_number(-v));
  } elseif (v == 0) {
    return msg.store_uint(48, 8);
  } else {
    return msg.store_number(digitize_number(v));
  }
}

​

(TVM assembly) Efficient modulo multiplication

;; First version
int mul_mod(int a, int b, int m) inline_ref {               ;; 1232 gas units
  (_, int r) = muldivmod(a % m, b % m, m);
  return r;
}

;; Second version
int mul_mod_better(int a, int b, int m) inline_ref {        ;; 1110 gas units
  (_, int r) = muldivmod(a, b, m);
  return r;
}

;; Third version, uses Fift to embed exact bitcode to be invoked later by the TVM
int mul_mod_best(int a, int b, int m) asm "x{A988} s,";     ;; 65 gas units