DISK I/O

FB II provides FN fileExists(fName$,fVol) which checks for the existence of a file named "fName$" in a folder whose WDrefNum% = fVol.

To check for the existence of a folder named "fldrName$" in a folder whose WDrefNum% = inThisWDrefNum%, I came up with:

CLEAR LOCAL
LOCAL FN folderExists%(fldrName$,inThisWDrefNum%)
  DIM copyWD%, indx%, pathName$, fldrExists%, itemName$
  DIM srchFldr$

  copyWD%       = inThisWDrefNum%
  indx%         = -1
  pathName$     = FN convertWDRef$("",copyWD%)

  LONG IF RIGHT$(fldrName$,1) <> ":"
    srchFldr$ = fldrName$ + ":"
  XELSE
    srchFldr$ = fldrName$
  END IF

  DO
    itemName$  = FILES$(indx,,pathName$,inThisWDrefNum%)
    DEC(indx)
    LONG IF RIGHT$(itemName$,1) = ":"
      LONG IF itemName$ = srchFldr$
        fldrExists% = _true
        itemName$ = ""
      XELSE
        fldrExists% = _false
      END IF
    XELSE
      fldrExists% = _false
    END IF

  UNTIL itemName$ = ""

END FN = fldrExists%

Is there a faster or more sensible way of doing this not using FILES$?

How about:

CLEAR LOCAL
LOCAL FN IsFileOrFolderThere(theFileOrFolderName$, vRefNum%)
  DIM pBlock.128

  pBlock.ioCompletion& = _nil
  pBlock.ioNamePtr&    = @theFileOrFolderName$
  pBlock.ioVRefNum%    = vRefNum%
  pBlock.ioDirID&      = 0                    
  pBlock.ioFDirIndex%  = 0                     
  osErr% = FN GETCATINFO(@pBlock)

END FN = osErr%

theFileOrFolderName$ = "SubFolder:"
osErr% = FN IsFileOrFolderThere(theFileOrFolderName$, <>)
PRINT "IsFileOrFolderThere:";osErr%

OR

theFileOrFolderName$ = "HD:Folder:SubFolder:"
osErr% = FN IsFileOrFolderThere(theFileOrFolderName$, 0)
PRINT "IsFileOrFolderThere:";osErr%

I would use FN GETCATINFO to do it. That will tell you (a) whether the named item exists and (b) (if it exists) whether it's a file or a folder. I assume that you want to return _false in cases where the named item exists but it's a file.

LOCAL FN FolderExists(fldrName$,inThisWDrefNum%)
  DIM pb.108, OSErr, itemExists, itsAFolder
  pb.ioNamePtr& = @fldrName$
  pb.ioVRefNum% = inThisWDrefNum%
  pb.ioDirID& = 0
  pb.ioDirIndex% = 0
  OSErr = FN GETCATINFO(@pb)
  itemExists = (OSErr = _noErr)
  itsAFolder = ((PEEK(@pb.ioFlAttrib) AND BIT(4)) <> 0)
END FN = itemExists AND itsAFolder