I am having trouble converting from a Byte Array to a Signed Integer in VB6. This would be simple to do with BitConverter in .NET but I'm not sure what to do with VB6.
Thanks
Unfortunately no built in function, you need to write one. Here is a quick sample to get you started.
Private Function BArrayToInt(ByRef bArray() As Byte) As Integer
Dim iReturn As Integer
Dim i As Integer
For i = 0 To UBound(bArray) - LBound(bArray)
iReturn = iReturn + bArray(i) * 2 ^ i
Next i
BArrayToInt = iReturn
End Function
CopyMemory
Air code (may crash your PC, cause dinosaur attack, etc).
Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As Any, _ source As Any, ByVal bytes As Long)
Dim a() As Byte
Dim n As Integer
'get the bytes somehow into a()
CopyMemory n, a(0), 2
Related
I'm investigating a memory leak in some old VB6 code that seems to be related to recordset objects, so I'm trying to get the reference counts on the objects. I found some code online that will give a count of references to an object, and it works for a home-grown class. But when I try to apply it to ADODB recordset objects, the count is always 1492925242. I've tried this in the existing app and then in a dummy app - always comes back with the same number (unless there are no references, then it's 0).
Here's the code that gets the reference count:
Private Declare Sub RtlMoveMemory Lib "kernel32" (dest As Any, src As Any, ByVal nbytes As Long)
Function objRefCnt(obj As IUnknown) As Long
If Not obj Is Nothing Then
RtlMoveMemory objRefCnt, ByVal ObjPtr(obj) + 4, 4
objRefCnt = objRefCnt - 2
Else
objRefCnt = 0
End If
End Function
Here's the code that calls it on ADODB recordsets:
Sub main()
Dim obj_1 As ADODB.Recordset
Dim obj_2 As ADODB.Recordset
Debug.Print objRefCnt(obj_1) ' 0
Set obj_1 = New ADODB.Recordset
Debug.Print objRefCnt(obj_1) ' 1
Set obj_2 = obj_1
Debug.Print objRefCnt(obj_1) ' 2
Debug.Print objRefCnt(obj_2) ' 2
Set obj_2 = New ADODB.Recordset
Debug.Print objRefCnt(obj_1) ' 1
Debug.Print objRefCnt(obj_2) ' 1
End Sub
This returns the following:
0
1492925242
1492925242
1492925242
1492925242
1492925242
But when I added a dummy class called Class1 that has a single property (an integer), and create obj_1 and obj_2 as Class1 objects, I get this:
0
1
2
2
1
1
Any ideas on how I can get a reference count on the ADODB recordsets?
Thanks in advance.
The code you found assumes the reference count is stored inside the object at offset 4. There is no such requirement. IUnknown defines methods, not where private variables must be stored (and the reference count is a private variable of an object).
The way to get the reference count (for testing purposes only) is to call IUnknown.Release.
In order to do that from VB6, find olelib.tlb on the Internet (Edanmo's OLE interfaces & functions), reference it, and have
Public Function GetRefCount(ByVal obj As olelib.IUnknown) As Long
obj.AddRef
GetRefCount = obj.Release - 2
End Function
Dim r1 As ADODB.Recordset
Dim r2 As ADODB.Recordset
Set r1 = New ADODB.Recordset
Set r2 = r1
MsgBox GetRefCount(r1) ' 2
It appears m_dwRefCount member variable of ADODB.Recordset instances is at offset 16.
Try this objRefCnt replacement:
Private Declare Sub RtlMoveMemory Lib "kernel32" (dest As Any, src As Any, ByVal nbytes As Long)
Function RecordsetRefCnt(rs As Recordset) As Long
If Not rs Is Nothing Then
RtlMoveMemory RecordsetRefCnt, ByVal ObjPtr(rs) + 16, 4
RecordsetRefCnt = RecordsetRefCnt - 1
Else
RecordsetRefCnt = 0
End If
End Function
JFYI, here is a AddRef/Release based GetRefCount impl without additional typelibs
Private Declare Function DispCallFunc Lib "oleaut32" (ByVal pvInstance As Long, ByVal oVft As Long, ByVal lCc As Long, ByVal vtReturn As VbVarType, ByVal cActuals As Long, prgVt As Any, prgpVarg As Any, pvargResult As Variant) As Long
Public Function GetRefCount(pUnk As IUnknown) As Long
Const CC_STDCALL As Long = 4
Dim vResult As Variant
Call DispCallFunc(ObjPtr(pUnk), 1 * 4, CC_STDCALL, vbLong, 0, ByVal 0, ByVal 0, 0)
Call DispCallFunc(ObjPtr(pUnk), 2 * 4, CC_STDCALL, vbLong, 0, ByVal 0, ByVal 0, vResult)
GetRefCount = vResult - 2
End Function
And here is the AddRef/Release based GetRefCount implementation without additional typelibs which also works with 64-bit VBA:
#If VBA7 Then
Private Declare PtrSafe Function DispCallFunc Lib "oleAut32.dll" (ByVal pvInstance As LongPtr, ByVal oVft As LongPtr, ByVal cc As Long, ByVal vtReturn As VbVarType, ByVal cActuals As Long, ByRef prgVt As Any, ByRef prgpVarg As Any, ByRef pvargResult As Variant) As Long
#Else
Private Declare Function DispCallFunc Lib "oleaut32.dll" (ByVal pvInstance As Long, ByVal oVft As Long, ByVal cc As Long, ByVal vtReturn As VbVarType, ByVal cActuals As Long, ByRef prgVt As Any, ByRef prgpVarg As Any, ByRef pvargResult As Variant) As Long
#End If
Public Function GetRefCount(ByRef pUnk As IUnknown) As Long
Const CC_STDCALL As Long = 4
#If Win64 Then
Const PTR_SIZE As Long = 8
#Else
Const PTR_SIZE As Long = 4
#End If
If pUnk Is Nothing Then Exit Function
Dim vResult As Variant
Call DispCallFunc(ObjPtr(pUnk), 1 * PTR_SIZE, CC_STDCALL, vbLong, 0, ByVal 0, ByVal 0, 0)
Call DispCallFunc(ObjPtr(pUnk), 2 * PTR_SIZE, CC_STDCALL, vbLong, 0, ByVal 0, ByVal 0, vResult)
GetRefCount = vResult - 2
End Function
I'm extremely unfamiliar with VB6 so please excuse the rookie question:
I'm attempting to turn a long into it's component bytes. In C it is simple because of the automatic truncation and the bitshift operators. For the life of me I cannot figure out how to do this in VB6.
Attempts so far have all generally looked something like this
sys1 = CByte(((sys & &HFF000000) / 16777216)) ' >> 24
sys2 = CByte(((sys & &HFF0000) / 65536)) ' >> 16
sys1 and sys2 are declared as Byte and sys is declared as Long
I'm getting a type mismatch exception when I try to do this. Anybody know how to convert a Long into 4 Bytes ??
Thanks
You divide correctly, but you forgot to mask out only the least significant bits.
Supply the word you want to divide into bytes, and the index (0 is least significant, 1 is next, etc.)
Private Function getByte(word As Long, index As Integer) As Byte
Dim lTemp As Long
' shift the desired bits to the 8 least significant
lTemp = word / (2 ^ (index * 8))
' perform a bit-mask to keep only the 8 least significant
lTemp = lTemp And 255
getByte = lTemp
End Function
Found on FreeVBCode.com. Not tested, sorry.
Option Explicit
Private Declare Sub CopyMemory Lib "kernel32" _
Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal _
Length As Long)
Public Function LongToByteArray(ByVal lng as Long) as Byte()
'Example:
'dim bytArr() as Byte
'dim iCtr as Integer
'bytArr = LongToByteArray(90121)
'For iCtr = 0 to Ubound(bytArr)
'Debug.Print bytArr(iCtr)
'Next
'******************************************
Dim ByteArray(0 to 3)as Byte
CopyMemory ByteArray(0), Byval VarPtr(Lng),Len(Lng)
LongToByteArray = ByteArray
End Function
You can convert between simple value types and Byte arrays by combining UDTs and the LSet statement.
Option Explicit
Private Type DataBytes
Bytes(3) As Byte
End Type
Private Type DataLong
Long As Long
End Type
Private DB As DataBytes
Private DL As DataLong
Private Sub cmdBytesToLong_Click()
Dim I As Integer
For I = 0 To 3
DB.Bytes(I) = CByte("&H" & txtBytes(I).Text)
Next
LSet DL = DB
txtLong.Text = CStr(DL.Long)
txtBytes(0).SetFocus
End Sub
Private Sub cmdLongToBytes_Click()
Dim I As Integer
DL.Long = CLng(txtLong.Text)
LSet DB = DL
For I = 0 To 3
txtBytes(I).Text = Right$("0" & Hex$(DB.Bytes(I)), 2)
Next
txtLong.SetFocus
End Sub
Other than looping from 1 to 32 and trying open each of them, is there a reliable way to get COM ports on the system?
I believe under modern windows environments you can find them in the registry under the following key HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM. I'm not sure of the correct way to specify registry keys. However I have only ever tested this on Windows XP.
Check out this article from Randy Birch's site: CreateFile: Determine Available COM Ports
There's also the approach of using an MSCOMM control: ConfigurePort: Determine Available COM Ports with the MSCOMM Control
The code's a bit too long for me to post here but the links have everything you need.
It's 1 to 255. Fastest you can do it is using QueryDosDevice like this
Option Explicit
'--- for CreateFile
Private Const GENERIC_READ As Long = &H80000000
Private Const GENERIC_WRITE As Long = &H40000000
Private Const OPEN_EXISTING As Long = 3
Private Const INVALID_HANDLE_VALUE As Long = -1
'--- error codes
Private Const ERROR_ACCESS_DENIED As Long = 5&
Private Const ERROR_GEN_FAILURE As Long = 31&
Private Const ERROR_SHARING_VIOLATION As Long = 32&
Private Const ERROR_SEM_TIMEOUT As Long = 121&
Private Declare Function QueryDosDevice Lib "kernel32" Alias "QueryDosDeviceA" (ByVal lpDeviceName As Long, ByVal lpTargetPath As String, ByVal ucchMax As Long) As Long
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, ByVal lpSecurityAttributes As Long, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Function PrintError(sFunc As String)
Debug.Print sFunc; ": "; Error
End Function
Public Function IsNT() As Boolean
IsNT = True
End Function
Public Function EnumSerialPorts() As Variant
Const FUNC_NAME As String = "EnumSerialPorts"
Dim sBuffer As String
Dim lIdx As Long
Dim hFile As Long
Dim vRet As Variant
Dim lCount As Long
On Error GoTo EH
ReDim vRet(0 To 255) As Variant
If IsNT Then
sBuffer = String$(100000, 1)
Call QueryDosDevice(0, sBuffer, Len(sBuffer))
sBuffer = Chr$(0) & sBuffer
For lIdx = 1 To 255
If InStr(1, sBuffer, Chr$(0) & "COM" & lIdx & Chr$(0), vbTextCompare) > 0 Then
vRet(lCount) = "COM" & lIdx
lCount = lCount + 1
End If
Next
Else
For lIdx = 1 To 255
hFile = CreateFile("COM" & lIdx, GENERIC_READ Or GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0)
If hFile = INVALID_HANDLE_VALUE Then
Select Case Err.LastDllError
Case ERROR_ACCESS_DENIED, ERROR_GEN_FAILURE, ERROR_SHARING_VIOLATION, ERROR_SEM_TIMEOUT
hFile = 0
End Select
Else
Call CloseHandle(hFile)
hFile = 0
End If
If hFile = 0 Then
vRet(lCount) = "COM" & lIdx
lCount = lCount + 1
End If
Next
End If
If lCount = 0 Then
EnumSerialPorts = Split(vbNullString)
Else
ReDim Preserve vRet(0 To lCount - 1) As Variant
EnumSerialPorts = vRet
End If
Exit Function
EH:
PrintError FUNC_NAME
Resume Next
End Function
The snippet falls back to CreateFile on 9x. IsNT function is stubbed for brevity.
Using VB6 or VBScript to enumerate available COM ports can be as simple as using VB.NET, and this can be done by enumerating values from registry path HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM. It's better than calling QueryDosDevice() and doing string comparison to filter out devices which's name is leading by COM since you will get something like CompositeBattery (or other stuff which have full upper case name leading by COM) that isn't a COM port. Another benefit of doing this is that the registry values also containing USB to COM devices, which could not be detected by using the codes such as WMIService.ExecQuery("Select * from Win32_SerialPort"). If you try to plug the USB to COM devices in or out of the computer, you can see the registry values also appear or disappear immediately, since it's keeping updated.
Option Explicit
Sub ListComPorts()
List1.Clear
Dim Registry As Object, Names As Variant, Types As Variant
Set Registry = GetObject("winmgmts:\\.\root\default:StdRegProv")
If Registry.EnumValues(&H80000002, "HARDWARE\DEVICEMAP\SERIALCOMM", Names, Types) <> 0 Then Exit Sub
Dim I As Long
If IsArray(Names) Then
For I = 0 To UBound(Names)
Dim PortName As Variant
Registry.GetStringValue &H80000002, "HARDWARE\DEVICEMAP\SERIALCOMM", Names(I), PortName
List1.AddItem PortName & " - " & Names(I)
Next
End If
End Sub
Private Sub Form_Load()
ListComPorts
End Sub
The code above is using StdRegProv class to enumerate the values of a registry key. I've tested the code in XP, Windows 7, Windows 10, and it works without any complainant. The items which were added to the Listbox looks like below:
COM1 - \Device\Serial0
COM3 - \Device\ProlificSerial0
The downside of this code is that it could not detect which port is already opened by other programs since every port could only be opened once. The way to detect a COM port is opened by another program or not can be done by calling the API CreateFile. Here is an example.
I know how to look up a hostname from an IPv4 in VB using the GetHostByAddr Windows API call (this works great). However, that function does not allow one to specify the DNS server to use. Sometimes the default company DNS servers are fine, but other times I need to specify an external DNS server for lookups, and I don't think doing a shell nslookup and parsing the output is the best method, here.
Note: this is actually going to be used as VBA code in an Excel workbook to help someone else do his job, and it's not worth writing a big application when some simple functionality is all he needs.
I thought I had possibly found an answer in the API call getnameinfo but careful reading seems to indicate it does not offer a servername parameter.
After some intense searching, I found reference to the pExtra parameter to the DNSQuery function. But I don't even know how to begin to use that in VB6.
Could anyone help me out in any way with doing a DNS lookup from VB6, specifying the servername to use?
A full working solution would of course be nice, but I'm willing to work: just point me in the right direction.
UPDATE: For some odd reason it didn't click that DNSQuery was a Windows API call. It just didn't sound like one. I certainly would have been able to make more headway on the problem if I'd gathered that one tiny detail.
Try this:
Option Explicit
Private Declare Function DnsQuery Lib "dnsapi" Alias "DnsQuery_A" (ByVal strname As String, ByVal wType As Integer, ByVal fOptions As Long, ByVal pServers As Long, ppQueryResultsSet As Long, ByVal pReserved As Long) As Long
Private Declare Function DnsRecordListFree Lib "dnsapi" (ByVal pDnsRecord As Long, ByVal FreeType As Long) As Long
Private Declare Function lstrlen Lib "kernel32" (ByVal straddress As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, ByVal Source As Long, ByVal Length As Long)
Private Declare Function inet_ntoa Lib "ws2_32.dll" (ByVal pIP As Long) As Long
Private Declare Function inet_addr Lib "ws2_32.dll" (ByVal sAddr As String) As Long
Private Const DnsFreeRecordList As Long = 1
Private Const DNS_TYPE_A As Long = &H1
Private Const DNS_QUERY_BYPASS_CACHE As Long = &H8
Private Type VBDnsRecord
pNext As Long
pName As Long
wType As Integer
wDataLength As Integer
flags As Long
dwTel As Long
dwReserved As Long
prt As Long
others(35) As Byte
End Type
Private Sub Command1_Click()
MsgBox Resolve("google.com", "208.67.222.222")
End Sub
Private Function Resolve(sAddr As String, Optional sDnsServers As String) As String
Dim pRecord As Long
Dim pNext As Long
Dim uRecord As VBDnsRecord
Dim lPtr As Long
Dim vSplit As Variant
Dim laServers() As Long
Dim pServers As Long
Dim sName As String
If LenB(sDnsServers) <> 0 Then
vSplit = Split(sDnsServers)
ReDim laServers(0 To UBound(vSplit) + 1)
laServers(0) = UBound(laServers)
For lPtr = 0 To UBound(vSplit)
laServers(lPtr + 1) = inet_addr(vSplit(lPtr))
Next
pServers = VarPtr(laServers(0))
End If
If DnsQuery(sAddr, DNS_TYPE_A, DNS_QUERY_BYPASS_CACHE, pServers, pRecord, 0) = 0 Then
pNext = pRecord
Do While pNext <> 0
Call CopyMemory(uRecord, pNext, Len(uRecord))
If uRecord.wType = DNS_TYPE_A Then
lPtr = inet_ntoa(uRecord.prt)
sName = String(lstrlen(lPtr), 0)
Call CopyMemory(ByVal sName, lPtr, Len(sName))
If LenB(Resolve) <> 0 Then
Resolve = Resolve & " "
End If
Resolve = Resolve & sName
End If
pNext = uRecord.pNext
Loop
Call DnsRecordListFree(pRecord, DnsFreeRecordList)
End If
End Function
It is not an answer, but very important note to wqw post:
Security Warning on lstrlen function (lines 5 & 55):
Using this function incorrectly can compromise the security of your
application. lstrlen assumes that lpString is a null-terminated
string, or NULL. If it is not, this could lead to a buffer overrun or
a denial of service attack against your application.
Consider using one of the following alternatives: StringCbLength or
StringCchLength.
You can use the DNS WMI provider to set the DNS of the system then use GetHostByAddr
I am trying to set a custom paper size by doing:
Printer.Height = 2160
Printer.Width = 11900
But it doesn't seen to have any effect. After setting this up, i ask for that values and it returns the default ones. And this:
Printer.PaperSize = 256
Returns an error...
Any ideas??
Either your printer doesn't allow these properties to be set, or you're exceeding their maximum allowed values. From the Visual Basic Reference
If you set the Height and Width
properties for a printer driver that
doesn't allow these properties to be
set, no error occurs and the size of
the paper remains as it was. If you
set Height and Width for a printer
driver that allows only certain values
to be specified, no error occurs and
the property is set to whatever the
driver allows. For example, you could
set Height to 150 and the driver would
set it to 144.
I don't know why you're getting an error when you set the Papersize property to 256. It works for me. Also, the documentation states, "Setting a printer's Height or Width property automatically sets PaperSize to vbPRPSUser.", which equals 256.
I was actually involved with the same problem but I just happen to find a breakthrough.
First you need to create a custom form that defines you custom paper size. Then, you need to
refer to Windows API to check the form name you've just created. You'll get the for name
from an array returned from a function and use the array index where the form name was found.
Finally use it as the value for printer.papersize
Example below:
Public Type PRINTER_DEFAULTS
pDatatype As Long
pDevMode As Long
DesiredAccess As Long
End Type
Public Type FORM_INFO_1
Flags As Long
pName As Long ' String
Size As SIZEL
ImageableArea As RECTL
End Type
Public Declare Function EnumForms Lib "winspool.drv" Alias "EnumFormsA" _
(ByVal hPrinter As Long, ByVal Level As Long, ByRef pForm As Any, _
ByVal cbBuf As Long, ByRef pcbNeeded As Long, _
ByRef pcReturned As Long) As Long
Public Declare Sub CopyMemory Lib "KERNEL32" Alias "RtlMoveMemory" _
(pDest As Any, pSource As Any, ByVal cbLength As Long)
Public Declare Sub Sleep Lib "KERNEL32" (ByVal dwMilliseconds As Long)
Public Declare Function OpenPrinter Lib "winspool.drv" Alias _
"OpenPrinterA" (ByVal pPrinterName As String, phPrinter As Long, _
pDefault As PRINTER_DEFAULTS) As Long
Public Declare Function ClosePrinter Lib "winspool.drv" _
(ByVal hPrinter As Long) As Long
Public Declare Function lstrcpy Lib "KERNEL32" Alias "lstrcpyA" _
(ByVal lpString1 As String, ByRef lpString2 As Long) As Long
'UDF
Public Function PtrCtoVbString(ByVal Add As Long) As String
Dim sTemp As String * 512, x As Long
x = lstrcpy(sTemp, ByVal Add)
If (InStr(1, sTemp, Chr(0)) = 0) Then
PtrCtoVbString = ""
Else
PtrCtoVbString = Left(sTemp, InStr(1, sTemp, Chr(0)) - 1)
End If
End Function
Public Function IsFormExist(ByVal DeviceName As String, ByVal isFormName As String, ByVal PrinterHandle As Long) As Long
Dim NumForms As Long, i As Long
Dim FI1 As FORM_INFO_1
Dim pd As PRINTER_DEFAULTS
Dim aFI1() As FORM_INFO_1 ' Working FI1 array
Dim Temp() As Byte ' Temp FI1 array
Dim FormIndex As Integer
Dim BytesNeeded As Long
Dim RetVal As Long
On Error GoTo cleanup
FormIndex = 0
ReDim aFI1(1)
' First call retrieves the BytesNeeded.
RetVal = OpenPrinter(DeviceName, PrinterHandle, pd)
If (RetVal = 0) Or (PrinterHandle = 0) Then
'Can't access current printer. Bail out doing nothing
Exit Function
End If
RetVal = EnumForms(PrinterHandle, 1, aFI1(0), 0&, BytesNeeded, NumForms)
ReDim Temp(BytesNeeded)
ReDim aFI1(BytesNeeded / Len(FI1))
' Second call actually enumerates the supported forms.
RetVal = EnumForms(PrinterHandle, 1, Temp(0), BytesNeeded, BytesNeeded, _
NumForms)
Call CopyMemory(aFI1(0), Temp(0), BytesNeeded)
For i = 0 To NumForms - 1
With aFI1(i)
If isFormName = PtrCtoVbString(.pName) Then
' Found the desired form
FormIndex = i + 1
Exit For
End If
End With
Next i
IsFormExist = FormIndex ' Returns the number when form is found.
cleanup:
'Release the printer handle
If (PrinterHandle <> 0) Then Call ClosePrinter(PrinterHandle)
End Function
'Here We Go
dim papercode as long, printername as string, formname as string
printername=printer.Devicename
formname = "myform"
papercode=IsFormExist(printername, formname, Printer.hdc)
if papercode<>0 then
printer.papersize=papercode
end if
Give it a try, good luck
Are you sure the error isn't related to the maximum print width of the printer itself? Many printers have a max print width of 8.25" (11880) to allow 1/4" margins on either side of a 8.5" wide paper.
Quickest way to check would be to simply set the print wide to 11880 or lower and see if it works.
Another possibility would be permissions to the printer. If it's a shared network resource it may be locked down.
The solution is to use windows 98. It does not work with win2k, neither winXP. The same code, the same printer.
Regards.
I'm testing this code, but I can not see the custom form I created using printers and scanners in the Control Panel Windows XP Professional SP3.
Note: I could check in regedit that this form exists and its ID is 512 in a string value and it contains the name of the form created in the printers control panel.
Why this function does not return my custom form, I am using an HP Laserjet 1020.