Binaryworld - GetRegistryValue - Read the value of a Registry key ... [ VB -> Windows ]

Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" _
  (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, _
  ByVal samDesired As Long, phkResult As Long) As Long
Private Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As _
  Long
Private Declare Function RegQueryValueEx Lib "advapi32.dll" Alias _
  "RegQueryValueExA" (ByVal hKey As Long, ByVal lpValueName As String, _
  ByVal lpReserved As Long, lpType As Long, lpData As Any, _
  lpcbData As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As _
  Any, source As Any, ByVal numBytes As Long)

Const KEY_READ = &H20019 ' ((READ_CONTROL Or KEY_QUERY_VALUE Or
             ' KEY_ENUMERATE_SUB_KEYS Or KEY_NOTIFY) And (Not
             ' SYNCHRONIZE))

Const REG_SZ = 1
Const REG_EXPAND_SZ = 2
Const REG_BINARY = 3
Const REG_DWORD = 4
Const REG_MULTI_SZ = 7
Const ERROR_MORE_DATA = 234

' Read a Registry value
'
' Use ValueName = "" for the default value
' If the value isn't there, it returns the DefaultValue
' argument, or Empty if the argument has been omitted
'
' Supports DWORD, REG_SZ, REG_EXPAND_SZ, REG_BINARY and REG_MULTI_SZ
' REG_MULTI_SZ values are returned as a null-delimited stream of strings
' (VB6 users can use SPlit to convert to an array of string)

Function GetRegistryValue(ByVal hKey As Long, ByVal KeyName As String, _
  ByVal ValueName As String, Optional DefaultValue As Variant) As Variant
  Dim handle As Long
  Dim resLong As Long
  Dim resString As String
  Dim resBinary() As Byte
  Dim length As Long
  Dim retVal As Long
  Dim valueType As Long

  ' Prepare the default result
  GetRegistryValue = IIf(IsMissing(DefaultValue), Empty, DefaultValue)

  ' Open the key, exit if not found.
  If RegOpenKeyEx(hKey, KeyName, 0, KEY_READ, handle) Then
    Exit Function
  End If

  ' prepare a 1K receiving resBinary
  length = 1024
  ReDim resBinary(0 To length - 1) As Byte

  ' read the registry key
  retVal = RegQueryValueEx(handle, ValueName, 0, valueType, resBinary(0), _
    length)
  ' if resBinary was too small, try again
  If retVal = ERROR_MORE_DATA Then
    ' enlarge the resBinary, and read the value again
    ReDim resBinary(0 To length - 1) As Byte
    retVal = RegQueryValueEx(handle, ValueName, 0, valueType, resBinary(0), _
      length)
  End If

  ' return a value corresponding to the value type
  Select Case valueType
    Case REG_DWORD
      CopyMemory resLong, resBinary(0), 4
      GetRegistryValue = resLong
    Case REG_SZ, REG_EXPAND_SZ
      ' copy everything but the trailing null char
      resString = Space$(length - 1)
      CopyMemory ByVal resString, resBinary(0), length - 1
      GetRegistryValue = resString
    Case REG_BINARY
      ' resize the result resBinary
      If length <> UBound(resBinary) + 1 Then
        ReDim Preserve resBinary(0 To length - 1) As Byte
      End If
      GetRegistryValue = resBinary()
    Case REG_MULTI_SZ
      ' copy everything but the 2 trailing null chars
      resString = Space$(length - 2)
      CopyMemory ByVal resString, resBinary(0), length - 2
      GetRegistryValue = resString
    Case Else
      RegCloseKey handle
      Err.Raise 1001, , "Unsupported value type"
  End Select

  ' close the registry key
  RegCloseKey handle
End Function