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B.4 Search in a string

 ; StrStr
 ; input, top of stack = string to search for
 ;        top of stack-1 = string to search in
 ; output, top of stack (replaces with the portion of the string remaining)
 ; modifies no other variables.
 ;
 ; Usage:
 ;   Push "this is a long ass string"
 ;   Push "ass"
 ;   Call StrStr
 ;   Pop $R0
 ;  ($R0 at this point is "ass string")

 Function StrStr
   Exch $R1 ; st=haystack,old$R1, $R1=needle
   Exch    ; st=old$R1,haystack
   Exch $R2 ; st=old$R1,old$R2, $R2=haystack
   Push $R3
   Push $R4
   Push $R5
   StrLen $R3 $R1
   StrCpy $R4 0
   ; $R1=needle
   ; $R2=haystack
   ; $R3=len(needle)
   ; $R4=cnt
   ; $R5=tmp
   loop:
     StrCpy $R5 $R2 $R3 $R4
     StrCmp $R5 $R1 done
     StrCmp $R5 "" done
     IntOp $R4 $R4 + 1
     Goto loop
 done:
   StrCpy $R1 $R2 "" $R4
   Pop $R5
   Pop $R4
   Pop $R3
   Pop $R2
   Exch $R1
 FunctionEnd

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