ACC2000: Enumerating Local and Network Printers (200611)

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Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. The code in each of the two examples performs these steps:

• Calls the EnumPrinters API, which returns a buffer of data, a success flag, and a flag indicating whether the buffer is too small.
• If the buffer is too small, the code makes it the correct size and calls the API again.
• For each entry in the buffer, it extracts the data and prints it.

NOTE: When using these functions in your own applications, you may want to return an array of data that can be displayed in a list box or grid rather than print the values.

The buffer is in the following format:

INFO records containing string pointers and numeric values are added from the left and the string text for each record is added from the right. The area between the end of the last record and the start of the last string text contains garbage.

The buffer is declared as type Long, which makes extracting data from the records easier - all fields are either Long or pointers (pointers map to Long).

The StrLen() and PtrToStr() functions are used to set up the receiving string variable and to copy the text from the buffer to the variable.

1. Create a module and type the following lines in the Declarations section:

   Option Compare Database
   Option Explicit
   
   Const PRINTER_ENUM_CONNECTIONS = &H4
   Const PRINTER_ENUM_LOCAL = &H2
   
   Type PRINTER_INFO_1
      flags As Long
      pDescription As String
      PName As String
      PComment As String
   End Type
   
   Type PRINTER_INFO_4
      pPrinterName As String
      pServerName As String
      Attributes As Long
   End Type
   
   Declare Function EnumPrinters Lib "winspool.drv" Alias _
      "EnumPrintersA" (ByVal flags As Long, ByVal name As String, _
      ByVal Level As Long, pPrinterEnum As Long, ByVal cdBuf As Long, _
      pcbNeeded As Long, pcReturned As Long) As Long
   Declare Function PtrToStr Lib "Kernel32" Alias "lstrcpyA" _
      (ByVal RetVal As String, ByVal Ptr As Long) As Long
   Declare Function StrLen Lib "Kernel32" Alias "lstrlenA" _
      (ByVal Ptr As Long) As Long
   					

2. Type the following procedures:

   Sub EnumeratePrintersWin()
   
      Dim Success As Boolean, cbRequired As Long, cbBuffer As Long
      Dim Buffer() As Long, nEntries As Long
      Dim I As Long, PFlags As Long, PDesc As String, PName As String
      Dim PComment As String, Temp As Long
   
      cbBuffer = 3072
      ReDim Buffer((cbBuffer \ 4) - 1) As Long
      Success = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
                            PRINTER_ENUM_LOCAL, _
                            vbNullString, _
                            1, _
                            Buffer(0), _
                            cbBuffer, _
                            cbRequired, _
                            nEntries)
      If Success Then
         If cbRequired > cbBuffer Then
            cbBuffer = cbRequired
            Debug.Print "Buffer too small.  Trying again with " & _
                     cbBuffer & " bytes."
            ReDim Buffer(cbBuffer \ 4) As Long
            Success = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
                                PRINTER_ENUM_LOCAL, _
                                vbNullString, _
                                1, _
                                Buffer(0), _
                                cbBuffer, _
                                cbRequired, _
                                nEntries)
            If Not Success Then
               Debug.Print "Error enumerating printers."
               Exit Sub
            End If
         End If
      Debug.Print "There are " & nEntries & _
                   " local and connected printers."
      For I = 0 To nEntries - 1
         PFlags = Buffer(4 * I)
         PDesc = Space$(StrLen(Buffer(I * 4 + 1)))
         Temp = PtrToStr(PDesc, Buffer(I * 4 + 1))
         PName = Space$(StrLen(Buffer(I * 4 + 2)))
         Temp = PtrToStr(PName, Buffer(I * 4 + 2))
         PComment = Space$(StrLen(Buffer(I * 4 + 2)))
         Temp = PtrToStr(PComment, Buffer(I * 4 + 2))
         Debug.Print PFlags, PDesc, PName, PComment
      Next I
      Else
         Debug.Print "Error enumerating printers."
      End If
   End Sub
   					

   
   

   Sub EnumeratePrintersNT()
   
      Dim Success As Boolean, cbRequired As Long, cbBuffer As Long
      Dim Buffer() As Long, nEntries As Long
      Dim I As Long, PName As String, SName As String
      Dim Attrib As Long, Temp As Long
   
      cbBuffer = 3072
      ReDim Buffer((cbBuffer \ 4) - 1) As Long
      Success = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
                            PRINTER_ENUM_LOCAL, _
                            vbNullString, _
                            4, _
                            Buffer(0), _
                            cbBuffer, _
                            cbRequired, _
                            nEntries)
      If Success Then
         If cbRequired > cbBuffer Then
            cbBuffer = cbRequired
            Debug.Print "Buffer too small.  Trying again with " & _
                     cbBuffer & " bytes."
            ReDim Buffer(cbBuffer \ 4) As Long
            Success = EnumPrinters(PRINTER_ENUM_CONNECTIONS Or _
                                PRINTER_ENUM_LOCAL, _
                                vbNullString, _
                                4, _
                                Buffer(0), _
                                cbBuffer, _
                                cbRequired, _
                                nEntries)
            If Not Success Then
               Debug.Print "Error enumerating printers."
               Exit Sub
            End If
         End If
         Debug.Print "There are " & nEntries & _
                   " local and connected printers."
         For I = 0 To nEntries - 1
         PName = Space$(StrLen(Buffer(I * 3)))
         Temp = PtrToStr(PName, Buffer(I * 3))
         SName = Space$(StrLen(Buffer(I * 3 + 1)))
         Temp = PtrToStr(SName, Buffer(I * 3 + 1))
         Attrib = Buffer(I * 3 + 2)
         Debug.Print "Printer: " & PName, "Server: " & SName, _
                     "Attributes: " & Hex$(Attrib)
         Next I
      Else
         Debug.Print "Error enumerating printers."
      End If
   End Sub
   					

3. To test this function, type the following line in the Immediate window, and then press ENTER:

   EnumeratePrintersWIN
   					

   The output should be similar to the following:
   

   There are 1 local and connected printers.
   8388608      \\NCPRINT\HP5SI@1155,HP LaserJet 5Si MX,HP5SI@1155
   \\NCPRINT\HP5SI@1155        \\NCPRINT\HP5SI@1155
   						

   If you are using Microsoft Windows NT, type:

   EnumeratePrintersNT
   					

   The output should be similar to the following:

   There are 1 local and connected printers.
   Printer: \\NCPRINT\HP5SI@1155             Server: \\NCPRINT
   Attributes: 10