; Adapted from: https://nsis.sourceforge.io/Another_String_Replace_(and_Slash/BackSlash_Converter) (2019-08-31)

!macro _StrSlashConstructor out in
  Push "${in}"
  Push "\"
  Call StrSlash
  Pop ${out}
!macroend

!define StrSlash '!insertmacro "_StrSlashConstructor"'

; Push $filenamestring (e.g. 'c:\this\and\that\filename.htm')
; Push "\"
; Call StrSlash
; Pop $R0
; ;Now $R0 contains 'c:/this/and/that/filename.htm'
Function StrSlash
  Exch $R3 ; $R3 = needle ("\" or "/")
  Exch
  Exch $R1 ; $R1 = String to replacement in (haystack)
  Push $R2 ; Replaced haystack
  Push $R4 ; $R4 = not $R3 ("/" or "\")
  Push $R6
  Push $R7 ; Scratch reg
  StrCpy $R2 ""
  StrLen $R6 $R1
  StrCpy $R4 "\"
  StrCmp $R3 "/" loop
  StrCpy $R4 "/"
loop:
  StrCpy $R7 $R1 1
  StrCpy $R1 $R1 $R6 1
  StrCmp $R7 $R3 found
  StrCpy $R2 "$R2$R7"
  StrCmp $R1 "" done loop
found:
  StrCpy $R2 "$R2$R4"
  StrCmp $R1 "" done loop
done:
  StrCpy $R3 $R2
  Pop $R7
  Pop $R6
  Pop $R4
  Pop $R2
  Pop $R1
  Exch $R3
FunctionEnd