AutoHotkey Community

RelativePath(MasterPath, SlavePath, s="\")
AbsolutePath(AbsolutPath, RelativePath, s="\")

RelativePath(MasterPath, SlavePath, s="\"){
    len := InStr(MasterPath, s, "", InStr(MasterPath, s . s) + 2) ;get server or drive string length
    If SubStr(MasterPath, 1, len ) <> SubStr(SlavePath, 1, len )  ;different server or drive
        Return SlavePath                                              ;return absolut path
    MasterPath := SubStr(MasterPath, len + 1 )                    ;remove server or drive from MasterPath
    SlavePath := SubStr(SlavePath, len + 1 )                      ;remove server or drive from SlavePath
    If InStr(MasterPath, s, "", 0) = StrLen(MasterPath)           ;remove last \ from MasterPath if any
        StringTrimRight, MasterPath, MasterPath, 1
    If InStr(SlavePath, s, "", 0) = StrLen(SlavePath)             ;remove last \ from SlavePath if any
        StringTrimRight, SlavePath, SlavePath, 1
    Loop{
        If !MasterPath                                            ;when there is nothing didentical
            Return s SlavePath                                         ;return SlavePath in root
        If InStr(SlavePath s, MasterPath s){                      ;when parts of paths match
            If !r                                                      ;no relative part yet
                r = .%s%                                                   ;SlavePath is in the MasterPath
            Return r . SubStr(SlavePath,StrLen(MasterPath) + 2)        ;return relative path
        }Else{                                                    ;otherwise
            r .= ".." s                                                ;add relative part
            MasterPath := SubStr(MasterPath, 1, InStr(MasterPath, s, "", 0) - 1)   ;remove one folder from MasterPath
          }
      }
  }

AbsolutePath(AbsolutPath, RelativePath, s="\") {
    len := InStr(AbsolutPath, s, "", InStr(AbsolutPath, s . s) + 2) - 1   ;get server or drive string length
    pr := SubStr(AbsolutPath, 1, len)                                     ;get server or drive name
    AbsolutPath := SubStr(AbsolutPath, len + 1)                           ;remove server or drive from AbsolutPath
    If InStr(AbsolutPath, s, "", 0) = StrLen(AbsolutPath)                 ;remove last \ from AbsolutPath if any
        StringTrimRight, AbsolutPath, AbsolutPath, 1
    If InStr(RelativePath, s, "", 0) = StrLen(RelativePath)               ;remove last \ from RelativePath if any
        StringTrimRight, RelativePath, RelativePath, 1
    If InStr(RelativePath, s) = 1                                         ;when first char is \ go to AbsolutPath of server or drive
        AbsolutPath := "", RelativePath := SubStr(RelativePath, 2)            ;set AbsolutPath to nothing and remove one char from RelativePath
    Else If InStr(RelativePath,"." s) = 1                                 ;when first two chars are .\ add to current AbsolutPath directory
        RelativePath := SubStr(RelativePath, 3)                               ;remove two chars from RelativePath
    Else {                                                                ;otherwise
        StringReplace, RelativePath, RelativePath, ..%s%, , UseErrorLevel     ;remove all ..\ from RelativePath
        Loop, %ErrorLevel%                                                    ;for all ..\
            AbsolutPath := SubStr(AbsolutPath, 1, InStr(AbsolutPath, s, "", 0) - 1)  ;remove one folder from AbsolutPath
      }
    Return, pr . AbsolutPath . s . RelativePath                             ;concatenate server + AbsolutPath + separator + RelativePath
  }

Path1 = \\server.com\user\Files\Docs\Code\AHK\SciTEDirector\includes
Path2 = \\server.com\user\Files\Docs\Code\AHK\SmartGui\no_commit\icons_dev
MsgBox, % RelativePath(Path1, Path2)
MsgBox, % RelativePath(Path2, Path1)
Path2 = \\server.com\user123\Files\Docs\Code\AHK\SmartGui\no_commit\icons_dev
MsgBox, % RelativePath(Path1, Path2)
MsgBox, % RelativePath(Path2, Path1)
Return

;return the relative path of Slavepath to Masterpath
RelativePath(MasterPath, SlavePath){
    ;remove last \ if there are any
    MasterPath := RegExReplace(MasterPath, "\\$")
    SlavePath  := RegExReplace(SlavePath, "\\$")

    ;create arrays
    StringSplit, MasterPath, MasterPath, \
    StringSplit, SlavePath, SlavePath, \
 
    ;sort out equivalent portions
    Loop, %MasterPath0%
        If (MasterPath%A_Index% = SlavePath%A_Index%)
            Same := A_Index
        Else
            Break
   
    ;build relative path       
    Loop, % MasterPath0 - Same
        RelativePath .= "..\"
   
    Loop, % SlavePath0 - Same {
        ID := Same + A_Index
        RelativePath .= SlavePath%ID% "\"   
      }
   
    Return RelativePath
  }

RelPath(root, dir) {
   ex := RegExReplace(dir, "(\\+[^\\]+)", "($1)?")
   StringReplace, ex, ex, \, \\, All
   pos := InStr(root, rel := RegExReplace(root, ex))
   Return, RegExReplace(rel, "\\[^\\]+", "..\") . SubStr(dir, pos + 1)
}

Path1 = \\server.com\user\Files\Docs\Code\AHK\SciTEDirector\includes
Path2 = \\server.com\user\Files\Docs\Code\AHK\SmartGui\no_commit\icons_dev
MsgBox, % "1: " RelativePath(Path1, Path2) "`n2: " RelPath(Path1, Path2)
MsgBox, % "1: " RelativePath(Path2, Path1) "`n2: " RelPath(Path2, Path1)
MsgBox, % "1: " RelativePath(Path1, Path1) "`n2: " RelPath(Path1, Path1) ;< supposed to be empty
Path1 = \\server.com\user\Files\Docs\Code\AHK\SciTEDirector\includes
Path2 = \\server.com\user\Files123\Docs\Code\AHK\SmartGui\no_commit\icons_dev
MsgBox, % "1: " RelativePath(Path1, Path2) "`n2: " RelPath(Path1, Path2)
MsgBox, % "1: " RelativePath(Path2, Path1) "`n2: " RelPath(Path2, Path1)
MsgBox, % "1: " RelativePath(Path1, Path1) "`n2: " RelPath(Path1, Path1) ;< supposed to be empty
Return

RelPath(root, dir) {
   Loop, Parse, dir, \
      If A_LoopField
         ex .= "(\\" . (d ? "\\" : "") . A_LoopField, ey .= "\b)?", d := 0
      Else d = 1
   Return, (pos := InStr(root, rel := RegExReplace(root, ex . ey)))
      and rel ? RegExReplace(rel, "\\[^\\]+", "..\") . SubStr(dir, pos + 1) : ""
}

MsgBox, % RelToAbs("\\server.com\user\Files\Docs\Code\AHK\SmartGui\no_commit\icons_dev", "..\..\..\SciTEDirector\includes\")
MsgBox, % RelToAbs("http://example.com/info/sec/", "../data/get.html", "/")
MsgBox, % RelToAbs("http://example.com/info/sec/", "/data/get.html", "/")

RelToAbs(root, dir, s = "\") {
   pr := SubStr(root, 1, len := InStr(root, s, "", InStr(root, s . s) + 2) - 1)
      , root := SubStr(root, len + 1), off := 0
   If InStr(root, s, "", 0) = StrLen(root)
      StringTrimRight, root, root, 1
   If InStr(dir, s, "", 0) = StrLen(dir)
      StringTrimRight, dir, dir, 1
   Loop, Parse, dir, %s%
      If InStr(A_LoopField, "..") = 1
         root := SubStr(root, 1, InStr(root, s, "", 0) - 1)
      Else If A_LoopField =
         root := "", dir := SubStr(dir, 2)
   StringReplace, dir, dir, ..%s%, , All
   Return, pr . root . s . dir
}

AbsolutePath(root, dir, s = "\") {
    ;remove last \ if there are any
    root := RegExReplace(root, "\Q" s "\E$")
    dir  := RegExReplace(dir, "\Q" s "\E$")
    ;remove first \ of relativepath if there is one
    dir  := RegExReplace(dir, "^\Q" s "\E")

    ;create arrays
    StringSplit, root, root, %s%
    StringSplit, dir, dir, %s%

    ;combine to new absolute path
    Count = 0
    Loop % Root0 + dir0 {
        If (A_Index <= dir0) {
            ID := Dir0 - A_Index + 1
            If (Dir%ID% <> "..")
                AbsolutePath := Dir%ID% . s . AbsolutePath
            Else Count++
        }Else{
            ID := Root0 + Dir0 - A_Index + 1 - Count
            If ID > 0
                AbsolutePath := Root%ID% . s . AbsolutePath
            Else Break
          }
      }
    Return RegExReplace(AbsolutePath, "\Q" s "\E$") ;remove last \
  }