I have an unsigned 32-bit word that contains bit-field data. The following C/C++ structure is an example of one 32-bit word broken into bit-fields. In VB .NET, is it possible to define bit-fields within a structure (similar to the one below) so that the data can be accessed by "abc.data1", "abc.data2", etc.?
typedefstruct
{
UINT32 data1 : 10;
UINT32 data2 : 6;
UINT32 data3 : 14;
UINT32 data4 : 2 ;
} A_32_BIT_WORD_S;
Forgive me, I am not real great with C, I only took one class in it a long time ago.
Assuming you just want to create a stucture made up of 4 unsigned integers, this should work as far as defining it
Public Structure A_32_BIT_WORD_S
Dim data1 As UInt32
Dim data2 As UInt32
Dim data3 As UInt32
Dim data4 As UInt32
End Structure
I am guessing 10,6,14,and 2 are the values being assigned to each Uint? In VB you can't assign inital values to the structure until you create a variable instance. So you would do something like this:
Private Sub DoSomething()
End SubDim MyWord As New A_32_BIT_WORD_S
With MyWord
.data1 = 10
.data2 = 6
.data3 = 14
.data4 = 2
End With
No...
I want "Dim abc as A_32_BIT_WORD_S" to be one 32-bit word. Then data1 is the first 10 bits of that word, data2 is the next 6 bits of the word, etc.
Hi,
The only way I can see of achieving this is to use BitWise AND operations within a CLASS like this.
The maxValue for a UInt32 is 4294967295 = ( 2 ^ 32 ) -1
Regards,
John.
Public Class Form1
'The next highlighted line should be one line of code in your code window.>>
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim myWord As New custom32BitWord
myWord.data1 = UInt32.MaxValue
myWord.data2 = UInt32.MaxValue
myWord.data3 = UInt32.MaxValue
myWord.data4 = UInt32.MaxValue
'Due to bitwise masking with the AND function in the CLASS
'below then these values should add up to Uint32.MaxValue Dim total As UInt32total = myWord.data1 + myWord.data2 + myWord.data3 + myWord.data4
MessageBox.Show(total.ToString)
MessageBox.Show(UInt32.MaxValue.ToString)
End SubEnd Class
Public Class custom32BitWord
Private dayta1, dayta2, dayta3, dayta4 As UInt32
Public Property data1()
Get
Return dayta1End Get Set(ByVal value)'1st 10 bits.dayta1 = value
And &HFFC00000 '= 11111111 11000000 00000000 00000000 End Set End Property
Public Property data2()
Get
Return dayta2End Get Set(ByVal value)'Next 6 bits.dayta2 = value
And &H3F0000 '= 00000000 00111111 00000000 00000000 End Set End Property
Public Property data3()
Get
Return dayta3End Get Set(ByVal value)'Next 14 bits.dayta3 = value
And &HFFFC '= 00000000 00000000 111111111 11111100 End Set End Property
Public Property data4()
Get
Return dayta4End Get Set(ByVal value)'Last 2 bits.dayta4 = value
And 3 '= 00000000 00000000 00000000 00000011 End Set End PropertyEnd Class
Module Module1
Public Structure A32BitWord
Public word As Integer
Public Property data1() As Integer
Get
Return ReadBits(word, 0, 10)
End Get
Set(ByVal value As Integer)
WriteBits(word, 0, 10, value)
End Set
End Property
' etc...
End Structure
Private Function ReadBits(ByVal word As Integer, ByVal offset As Integer, ByVal bits As Integer) As Integer
Dim mask As Integer = ((1 << bits) - 1) << offset
Return (word And mask) >> offset
End Function
Private Sub WriteBits(ByRef word As Integer, ByVal offset As Integer, ByVal bits As Integer, ByVal value As Integer)
Dim mask As Integer = ((1 << bits) - 1) << offset
value = (value << offset) And mask
word = (word And Not mask) Or value
End Sub
End Module
