How To Retrieve Individual Bytes from a Multi-Byte Type in VB

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This code shows how to move the separate bytes of a long integer into a four-element byte array and also how to turn the byte array back into a long integer. In a Visual Basic project, place the following code in the declarations section:

   Private Declare Sub CopyMemory Lib "Kernel32" Alias "RtlMoveMemory" ( _
           ByRef Destination As Any, _
           ByRef Source As Any, _
           ByVal numbytes As Long)
				

A long integer consists of four bytes. These four bytes are recognized by Visual Basic to be one number. Use the following subroutine to move the individual bytes into a byte array:

   Public Sub LongToBytes(ByRef TheArray() As Byte, ByRef TheLong As Long)

     Call CopyMemory(TheArray(LBound(TheArray)), TheLong, 4)

   End Sub
				

The first parameter passed to CopyMemory is the first element of the array into which the bytes will be stored. (NOTE: The entire array is passed to longToBytes.) The second parameter is the source variable. The third parameter is how many bytes will be moved. Because a long integer consists of four bytes, this parameter has been set to 4.

To go the other way, turning a byte array back into a long integer variable, use the following code:

    Public Function BytesToLong(TheArray() As Byte) As Long
   Dim TempLong As Long

     Call CopyMemory(TempLong, TheArray(LBound(TheArray)), 4)
     BytesToLong = TempLong

   End Function
				

NOTE: As with any API call, passing improper memory addresses can cause data corruption or could cause your program to terminate abnormally.