FolderExists Issue

[k_zeon]

Hi All

I recently started to get some errors in my Folderexists function. If the Folder name was not the same case it would cause it to return False.

Private Const MAX_PATH As Long = 260
Private Const INVALID_HANDLE_VALUE As Long = -1
Private Const FILE_ATTRIBUTE_DIRECTORY As Long = &H10

Private Type FILETIME
    dwLowDateTime As Long
    dwHighDateTime As Long
End Type


Private Type WIN32_FIND_DATA
    dwFileAttributes As Long
    ftCreationTime As FILETIME
    ftLastAccessTime As FILETIME
    ftLastWriteTime As FILETIME
    nFileSizeHigh As Long
    nFileSizeLow As Long
    dwReserved0 As Long
    dwReserved1 As Long
    cFileName As String * MAX_PATH
    cAlternate As String * 14
End Type



Private Declare Function FindFirstFile Lib "kernel32" _
() '                                       Alias "FindFirstFileA" _
                                       (ByVal lpFileName As String, _
                                        lpFindFileData As WIN32_FIND_DATA) As Long

Private Declare Function FindClose Lib "kernel32" _
() '                                   (ByVal hFindFile As Long) As Long



Public Function FolderExists(sFolder As String) As Boolean

    Dim hFile As Long
    Dim WFD As WIN32_FIND_DATA

    'remove training slash before verifying
    sFolder = UnQualifyPath(sFolder)

    'call the API pasing the folder
    hFile = FindFirstFile(sFolder, WFD)

    'if a valid file handle was returned,
    'and the directory attribute is set
    'the folder exists
    FolderExists = (hFile <> INVALID_HANDLE_VALUE) And _
                   (WFD.dwFileAttributes And FILE_ATTRIBUTE_DIRECTORY)

    'clean up
    Call FindClose(hFile)

End Function

Private Function UnQualifyPath(ByVal sFolder As String) As String

'trim and remove any trailing slash
    sFolder = Trim$(sFolder)

    If Right$(sFolder, 1) = "\" Then
        UnQualifyPath = Left$(sFolder, Len(sFolder) - 1)
    Else
        UnQualifyPath = sFolder
    End If

End Function

i then swapped to

Private Declare Function PathIsDirectory Lib "shlwapi.dll" Alias "PathIsDirectoryA" _
(ByVal pszPath As String) As Long


Public Function FolderExists(ByVal sFolder As String) As Boolean
    FolderExists = PathIsDirectory(sFolder)
End Function

and it works fine.

Why would the first example now say False if case is incorrect but the folder path is correct.

tks

[VanGoghGaming]

Public Function FolderExists(sFolder As String) As Boolean
Dim FolderAttributes As Long
    FolderAttributes = GetFileAttributesW(StrPtr(sFolder))
    If FolderAttributes <> INVALID_HANDLE_VALUE Then FolderExists = (FolderAttributes And FILE_ATTRIBUTE_DIRECTORY) = FILE_ATTRIBUTE_DIRECTORY
End Function

[-Franky-]

I like to use the SHParseDisplayName or SHCreateItemFromParsingName API for this. If the return value is not equal to S_OK, the path does not exist. Another advantage of the API is that it can handle paths that do not have a drive letter.

[baka]

also FindFirstFileA is the old one, u should use FindFirstFileW.
I use FindFirstFileA only in my own folders that I know is VB6 friendly.
the folder is shortpath converted as well.

but, if u deal with unknown folders, u need to use Unicode aware.

[VanGoghGaming]

And of course the WinRT solution:

Public Function FolderExists(sFolder As String) As Boolean
    With New cAwait
        FolderExists = .Await(StorageFolderStatics.GetFolderFromPathAsync(StrRef(sFolder))) = AsyncStatus_Completed
    End With
End Function

Doesn't block the thread in case of unreachable network paths!

[Eduardo-]

And of course the WinRT solution:

Public Function FolderExists(sFolder As String) As Boolean
    With New cAwait
        FolderExists = .Await(StorageFolderStatics.GetFolderFromPathAsync(StrRef(sFolder))) = AsyncStatus_Completed
    End With
End Function

Doesn't block the thread in case of unreachable network paths!

But that can be also a problem if you don't want that, because you can receive events. Similar to having a DoEvents.

[VanGoghGaming]

It's not similar to having a DoEvents, it is exactly that!

Generally it is preferred to have a responsive UI rather than a frozen one but it is up to the developer to manage reentrancy problems. One major advantage is that it allows the user to cancel pending operations.

If you use an existing instance of the cAwait class, it is smart enough not to initiate another async operation while a previous one is still being awaited and the Cancel method can be used to abort the current async operation.

[k_zeon]

i have noticed though that in the same app i changed the folderexists, i came across another issue.

I used the following (part of code) to check a file exists, if yes then pass to CImageInfo.

 If FileExists(MyData.Fanart) = True Then
            Dim AA As New CImageInfo
            AA.ReadImageInfo MyData.Fanart

MyData.Fanart = "C\xxx\xxx\Fanart.jpg" (created in code) and the Fileexists finds it so passes on to the following function. but it errors out at m_Size = ConvertBytes(FileLen(sFileName), 2, True)
with path not found. In the folder is fanart.jpg and if i change the lowercase f to uppercase F and rerun the code works fine. as soon as i put it back to lower case f it fails.

Public Sub ReadImageInfo(sFileName As String)

' This is the sub to call to retrieve information on a file.

' Byte array buffer to store part of the file
    Dim bBuf(BUFFERSIZE) As Byte
    ' Open file number
    Dim iFN As Integer

    ' Set all properties to default values
    m_Width = 0
    m_Height = 0
    m_Depth = 0
    m_ImageType = itUNKNOWN

    ' here we will load the first part of a file into a byte
    'array the amount of the file stored here depends on
    'the BUFFERSIZE constant
    iFN = FreeFile
    Open sFileName For Binary As iFN
    Get #iFN, 1, bBuf()
    Close iFN

    'get filesize of image
    m_Size = ConvertBytes(FileLen(sFileName), 2, True) ' fails if filename is not the exact upper and lower case.

'more code her etc

any one have any ideas why this would suddenly start happening. is MS being more strict. ?

[Arnoutdv]

Are your api declarations really this

Private Declare Function FindFirstFile Lib "kernel32" _
() '                                       Alias "FindFirstFileA" _
                                       (ByVal lpFileName As String, _
                                        lpFindFileData As WIN32_FIND_DATA) As Long

Private Declare Function FindClose Lib "kernel32" _
() '                                   (ByVal hFindFile As Long) As Long

[Eduardo-]

It's not similar to having a DoEvents, it is exactly that!

Generally it is preferred to have a responsive UI rather than a frozen one but it is up to the developer to manage reentrancy problems. One major advantage is that it allows the user to cancel pending operations.

If you use an existing instance of the cAwait class, it is smart enough not to initiate another async operation while a previous one is still being awaited and the Cancel method can be used to abort the current async operation.

Some days ago I was debugging an issue in a program. It turned out that in the Form_Load I used a function that ended using another function that I was not aware that it worked async. It had been made by Claude:

'==========================================================================
' Run a VBScript in hidden mode and reads the first line of the output.
'==========================================================================
Private Function RunVBSAndGetResult(ByVal iTempPath As String, ByVal iResultPath As String) As String
    Dim wsh As Object, fso As Object, ts As Object
    Set wsh = CreateObject("WScript.Shell")
    Set fso = CreateObject("Scripting.FileSystemObject")
    wsh.Run "wscript " & VBSQuote(iTempPath), 0, True   ' 0=hidden, True=wait
    RunVBSAndGetResult = ""
    If fso.FileExists(iResultPath) Then
        Set ts = fso.OpenTextFile(iResultPath, 1)       ' 1 = ForReading
        If Not ts.AtEndOfStream Then RunVBSAndGetResult = Trim(ts.ReadLine)
        ts.Close
    End If
End Function

To fix that issue that I was having, I moved that code that was in Form_Load to a timer. It needed to run when program starts but not necessarily in the Form_Load.
I mean, one needs to be aware of the async calls, they change the game.