test.wat

;; JSの16進数字列からi64値に変換する
  (func $hexArrayToi64 
    ;; 引数
    (param $length i32)(param $outoffset i32)(param $sign i32)
    ;; 戻り値
    (result i32) 
    ;; ローカル変数
    (local $offset i32) (local $l i32) (local $temp i64)

    (local.set $l (i32.shl (local.get $length) (i32.const 1)))  
    (block $exit 
      (loop $loop
        (br_if $exit (i32.le_u (local.get $l) (local.get $offset)))
        (i64.shl (local.get $temp) (i64.const 4)) ;; shift 4bit (=x16)
        (if (result i64) 
          ;; 0-9(0x30-0x39)
          (i32.and 
            (i64.gt_u (i64.load16_u (local.get $offset)) (i64.const 0x30))
            (i64.le_u (i64.load16_u (local.get $offset)) (i64.const 0x39))
          )
          (then
            (i64.sub(i64.load16_u (local.get $offset)) (i64.const 0x30))
          )
          (else
           (if (result i64)
            ;; A-F (0x41-0x46)
            (i32.and 
              (i64.gt_u (i64.load16_u (local.get $offset)) (i64.const 0x41))
              (i64.le_u (i64.load16_u (local.get $offset)) (i64.const 0x46))
            )
            (then
              (i64.sub(i64.load16_u (local.get $offset)) (i64.const 35))
            )
            (else 
              (if (result i64)
                ;; a-f (0x61-0x66)
                (i32.and
                  (i64.gt_u (i64.load16_u (local.get $offset)) (i64.const 0x61))
                  (i64.le_u (i64.load16_u (local.get $offset)) (i64.const 0x66))
                )
                (then
                  (i64.sub(i64.load16_u (local.get $offset)) (i64.const 87))
                )
                (else
                  ;; 16進数文字以外が含まれている場合エラーを返して終了。
                  i32.const 0
                  return
                )
              )
            )
           )
          )
        ) 
        (i64.add)
        (local.set $temp)
        (local.set $offset (i32.add (local.get $offset) (i32.const 2)))
        (br $loop)
      )
    )
    (if 
      (i32.eqz (local.get $sign))
      (then
        ;; ＋の場合
        (i64.store (local.get $outoffset) (local.get $temp))
      )
      (else
        ;; -の場合
        (i64.store (local.get $outoffset) (i64.sub (i64.const 0) (local.get $temp)))
      )
    )   
    (i32.const 1)
  )