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; -- Convert an absolute path to a relative one.
; Tested with PB 4.51 on Windows XP and Ubuntu 10.04

CompilerSelect #PB_Compiler_OS
   CompilerCase #PB_OS_Windows
      #Slash = '\'
      #BadSlash = '/'
   CompilerDefault
      #Slash = '/'
      #BadSlash = '\'
CompilerEndSelect

Procedure.i EqualPathLen (s1$, s2$)
   ; -- return length of identical part of the paths in s1$ and s2$
   Protected maxEqual, temp, equal, ret
   Protected *p1.Character, *p2.Character
   
   CompilerIf #PB_Compiler_OS = #PB_OS_Windows
      s1$ = UCase(s1$)
      s2$ = UCase(s2$)
   CompilerEndIf
   
   maxEqual = Len(s1$)
   temp = Len(s2$)
   If maxEqual > temp
      maxEqual = temp
   EndIf
   
   *p1 = @s1$
   *p2 = @s2$
   equal = 0
   ret = 0
   While equal < maxEqual And *p1\c = *p2\c
      equal + 1
      If *p1\c = #Slash
         ret = equal
      EndIf   
      *p1 + SizeOf(character)
      *p2 + SizeOf(character)
   Wend
   
   ProcedureReturn ret
EndProcedure

Procedure.s RelativePath (baseDir$, absPath$)
   ; -- convert an absolute path to a relative one
   ; in : baseDir$: full name of a directory, with trailing (back)slash
   ;      absPath$: full name of a path to a directory or file
   ; out: absPath$ converted, so that it is relative to baseDir$
   Protected equal, s, i, parent$, ret$=""
   
   CompilerIf #PB_Compiler_OS = #PB_OS_Windows
      If UCase(Left(baseDir$, 1)) <> UCase(Left(absPath$, 1))
         ProcedureReturn absPath$  ; can't build a relative path
      EndIf
   CompilerEndIf

   ReplaceString(baseDir$, Chr(#BadSlash), Chr(#Slash), #PB_String_InPlace)
   ReplaceString(absPath$, Chr(#BadSlash), Chr(#Slash), #PB_String_InPlace)
   equal = EqualPathLen(baseDir$, absPath$)
   
   s = CountString(Mid(baseDir$, equal+1), Chr(#Slash))
   parent$ = ".." + Chr(#Slash)
   For i = 1 To s
      ret$ + parent$
   Next   
   
   ProcedureReturn ret$ + Mid(absPath$, equal+1)
EndProcedure


;-- Demo
CompilerSelect #PB_Compiler_OS
   CompilerCase #PB_OS_Windows
      Debug RelativePath("F:\Data\John\", "f:\Data\John\PC")
      Debug RelativePath("F:\Data\John\", "f:\Data\John\")
      Debug RelativePath("F:\Data\John\", "f:\Data\John")
      Debug RelativePath("F:\Data\John\", "f:\Data\Peter\")
      Debug RelativePath("F:\Data\John\", "f:\")
      Debug RelativePath("F:\", "f:\Data\John\")
      Debug RelativePath("F:\Data\John\", "g:\Videos")
   CompilerDefault
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Corsair/Data/John/PC")
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Corsair/Data/John/")
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Corsair/Data/John")
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Corsair/Data/Peter/")
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Corsair/")
      Debug RelativePath("/media/Corsair/", "/media/Corsair/Data/John/")
      Debug RelativePath("/media/Corsair/Data/John/", "/media/Maxtor/Videos")
CompilerEndSelect

Code: Select all

szOut.s=Space(#MAX_PATH)
szFrom.s = "c:\\a\\b\\path";
szTo.s = "c:\\a\\x\\y\\file";

PathRelativePathTo_(@szOut,szFrom,#FILE_ATTRIBUTE_DIRECTORY,szTo,#FILE_ATTRIBUTE_NORMAL);
Debug szOut
; OUTPUT:
; ==================
; The relative path is relative from: c:\a\b\path
; The relative path is relative To: c:\a\x\y\file
; The relative path is: ..\..\x\y\file

Code: Select all

<Include constants and procedures from the first post of this thread here>

Define ret.s{#MAX_PATH}

Debug "PathRelativePathTo_():"
Debug "----------------------"
PathRelativePathTo_(@ret, @"F:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\Data\John\pc.txt", #FILE_ATTRIBUTE_NORMAL)
Debug ret
PathRelativePathTo_(@ret, @"F:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY)
Debug ret
PathRelativePathTo_(@ret, @"F:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\Data\John", #FILE_ATTRIBUTE_NORMAL)
Debug ret
PathRelativePathTo_(@ret, @"F:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\Data\Peter\", #FILE_ATTRIBUTE_DIRECTORY)
Debug ret
PathRelativePathTo_(@ret, @"F:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\", #FILE_ATTRIBUTE_DIRECTORY)
Debug ret
PathRelativePathTo_(@ret, @"F:\", #FILE_ATTRIBUTE_DIRECTORY, @"f:\Data\John\", #FILE_ATTRIBUTE_DIRECTORY)
Debug ret
Debug ""
Debug ""
Debug "RelativePath():"
Debug "---------------"
Debug RelativePath("F:\Data\John\", "f:\Data\John\pc.txt")
Debug RelativePath("F:\Data\John\", "f:\Data\John\")
Debug RelativePath("F:\Data\John\", "f:\Data\John")
Debug RelativePath("F:\Data\John\", "f:\Data\Peter\")
Debug RelativePath("F:\Data\John\", "f:\")
Debug RelativePath("F:\", "f:\Data\John\")

Code: Select all

PathRelativePathTo_():
----------------------
\pc.txt
.
..\John
..\Peter\
..\..
.\Data\John\


RelativePath():
---------------
pc.txt

..\John
..\Peter\
..\..\
Data\John\