Visual Basic

Dave Kreskowiak wrote:

May I ask to what end are you doing this? Why go through all of this trouble when the functionality of it is wrapper in the System.Io.FileInfo class?

Dave Kreskowiak wrote:

Your return type for the Declare is wrong. You've got it as Long when it returns an Int32.

treddie wrote:

System.Io.FileInfo is limited to the MAX_PATH =260 barrier, as far as I can
tell.

treddie wrote:

I tried Int32, but the function returns -1 in that case. However, using Long
seems completely wrong too, because the function is inside a 32bit set of
libraries...win32. So it can't deal with a 64bit Long.

Dave Kreskowiak wrote:

that's because it's the limit in Windows, not .NET. The current path limit is 248 characters and the filename limit is 260.

treddie wrote:

string variable cannot contain Unicode characters

treddie wrote:

for example, "\\?\UNC\d:\?????????\*

treddie wrote:

Now I think I see why the string parameter needs to be changed to a pointer to
the path, rather than a string representing the path

Dave Kreskowiak wrote:

string variable cannot contain Unicode characters

Dave Kreskowiak wrote:

You never pass a "string".

treddie wrote:

But why do they declare strings in any function that accepts them?

treddie wrote:

I also found through tests that the TRUE limit for Windows, is 240 characters
max.

treddie wrote:

This may be a bug in Windows

Dave Kreskowiak wrote:

I also found through tests that the TRUE limit for Windows, is 240 characters

max.

Dim LPWSTR As UnmanagedType
Dim MyUnicodePointer As New MarshalAsAttribute(LPWSTR)

Dim MyStringPtr As Long = Marshal.StringToHGlobalAuto(MyString)

<VBFixedString(MAX_PATH), MarshalAs(UnmanagedType.ByValTStr, SizeConst:=MAX_PATH)> Public cFileName As String

Imports System.Runtime.InteropServices

Public Class Form1
   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      TreeView1.Nodes.Add(DriveToTreeNode("c"c))
   End Sub

   Private Sub TreeView1_AfterCollapse(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterCollapse
      e.Node.Nodes.Clear()
      e.Node.Nodes.Add(New TreeNode With {.Tag = New NodeData With {.IsDirectory = True}}) ' add dummy node
   End Sub

   Private Sub TreeView1_BeforeExpand(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewCancelEventArgs) Handles TreeView1.BeforeExpand
      ' only directories can have nodes
      e.Node.Nodes.Clear()
      EnumerateDirectory(e.Node)
   End Sub

   Private Sub TreeView1_MouseDoubleClick(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TreeView1.MouseDoubleClick
      If e.Button = Windows.Forms.MouseButtons.Left Then
         Dim hti As TreeViewHitTestInfo = TreeView1.HitTest(TreeView1.PointToClient(MousePosition))
         If CType(hti.Node.Tag, NodeData).IsFile Then
            Dim fullpath As String = CType(hti.Node.Parent.Tag, NodeData).DirectoryPath & hti.Node.Text
            MessageBox.Show("Long Path: " & fullpath & vbCrLf & "Path Length: " & fullpath.Length.ToString() & _
                            vbCrLf & "Short Name: " & GetShortPathName(fullpath), _
                            hti.Node.Text, MessageBoxButtons.OK)
         End If
      End If
   End Sub

#Region "Drive Enumeration"
   Private Function DriveToTreeNode(ByVal drive As Char) As TreeNode
      Dim node As New TreeNode
      node.Text = drive.ToString().ToUpper()
      node.Tag = New NodeData With {.IsDirectory = True, .DirectoryPath = node.Text & ":\"}
      ' recursing all filedirectories would take too long for a drive
      ' so will handle it on each directory node expansion
      EnumerateDirectory(node, recursedirectories:=False)
      Return node
   End Function

   ' see: Naming Files, Paths, and Namespaces
   ' Maximum Path Length Limitation
   ' http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx#maxpath
   Private Const LongPathPrefix As String = "\\?\"

   Private Sub EnumerateDirectory(ByVal node As TreeNode, Optional ByVal recursedirectories As Boolean = False)
      Dim path As String = CType(node.Tag, NodeData).DirectoryPath
      Dim findData As New WIN32_FIND_DATA

      Dim hFile As Microsoft.Win32.SafeHandles.SafeFileHandle
      hFile = FindFirstFile(LongPathPrefix & path & "*", findData)

      If hFile.DangerousGetHandle.ToInt32 = -1 Then
         ' just ignoring errors for this demo, most common is 5 - Access Denied
         ' System Error Codes
         ' http://msdn.microsoft.com/en-us/library/windows/desktop/ms681381%28v=vs.85%29.aspx
         'Dim [error] As Int32 = Marshal.GetLastWin32Error()
         'Stop
         Return
      Else
         Do
            If IsFlagSet(findData.dwFileAttributes, IO.FileAttributes.Directory) Then
               If findData.cFileName = "." Then Continue Do
               If findData.cFileName = ".." Then Continue Do
               Dim subdir As New TreeNode With {.Text = findData.cFileName, _
                                                .Tag = New NodeData With {.IsDirectory = True, _
                                                                           .DirectoryPath = path & findData.cFileName & "\" _
                                                                         } _
                                               }
               If recursedirectories Then
                  EnumerateDirectory(subdir, recursedirectories)
               Else
                  ' need to add a dummy node to make it expandable
                  subdir.Nodes.Add(New TreeNode With {.Tag = New NodeData With {.IsDirectory = True}})
               End If
               node.Nodes.Add(subdir)
            Else ' Filename
               node.Nodes.Add(New TreeNode With {.Text = findData.cFileName, .Tag = New NodeData With {.IsDirectory = False}})
            End If

         Loop While FindNextFile(hFile, findData)

         FindClose(hFile) ' make sure to close the handle
      End If

   End Sub

   Private Function IsFlagSet(ByVal value As System.ValueType, ByVal testflag As System.ValueType) As Boolean
      Dim val As UInt32 = CType(value, UInt32)
      Dim flag As UInt32 = CType(testflag, UInt32)
      Return (val And flag) = flag
   End Function

   <DllImport("kernel32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, EntryPoint:="FindFirstFile")> _
   Private Shared Function FindFirstFile(<System.Runtime.InteropServices.In(), MarshalAs(UnmanagedType.LPWStr)> ByVal fileName As String, _
                                         <[In](), Out(), MarshalAs(UnmanagedType.LPStruct)> ByVal data As WIN32_FIND_DATA) As Microsoft.Win32.SafeHandles.SafeFileHandle
   End Function

   <DllImport("kernel32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, EntryPoint:="FindNextFileW")> _
   Private Shared Function FindNextFile(ByVal hFindFile As Microsoft.Win32.SafeHandles.SafeFileHandle, _
                                        <[In](), Out(), MarshalAs(UnmanagedType.LPStruct)> ByVal ByvallpFindFileData As WIN32_FIND_DATA) As Boolean
   End Function

   <DllImport("kernel32.dll")> _
   Private Shared Function FindClose(ByVal hFindFile As Microsoft.Win32.SafeHandles.SafeFileHandle) As Boolean
   End Function

   <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
   Private Shared Function GetShortPathName(ByVal longPath As String, _
                                            <MarshalAs(UnmanagedType.LPTStr)> ByVal ShortPath As System.Text.StringBuilder, _
                                            <MarshalAs(Runtime.InteropServices.UnmanagedType.U4)> ByVal bufferSize As Integer) As Integer
   End Function

Quote:

In the ANSI version of this function, the name is limited to MAX_PATH characters. To extend this limit to 32,767 wide characters, call the Unicode version of the function and prepend "\\?\" to the path. For more information, see Naming a File.