; Pushes the length of s
; s -> b
.label length
   POPxw ; store start address
   $00 POPx ; counter
   .label length.loop
     ; if at end of string, go to end
     LDBxw $00 EQU length.end JCNw
     ; otherwise increment address and counter
     INCxw
     INCx
     length.loop JMPw
     .label length.end
       PSHx RTS