EnsureEndsWith

Here's a macro that I wrote, may be helpful to others. Sometimes when you get user input, it's important to ensure that it ends with a particular string (I.E. ".TXT" for a filename, or "\" for a path).

This macro ensures that the value in VALUE ends with the string END_WITH. If VALUE is "Test" and END_WITH is "\" then this will change VALUE to "Test\". On the other hand, if VALUE was "Test2\", it would be unchanged.

!MACRO EnsureEndsWith VALUE END_WITH
  Push $R0
  Push $R1
  Push $R2
 
  StrLen $R0 ${END_WITH} ; how long is the ending string
  IntOp $R1 0 - $R0   ; how far to offset back from the end of the string
  StrCpy $R2 ${VALUE} $R0 $R1 ;take N chars starting N from the end of VALUE put in R2
  StrCmp $R2 ${END_WITH} +2 ;if the last N chars = END_WITH, good.
    StrCpy ${VALUE} "${VALUE}${END_WITH}" ; otherwise, append END_WITH
 
  Pop $R2
  Pop $R1
  Pop $R0
!MACROEND