As explained in the tip about the ARGBColor structure (look at the end of this tip for the link), we can define a structure and have its fields that point to the same memory address, but that read a different number of bytes. This makes easier to define a structure that allows us to set a value to a field, and then retrieve the single bytes/words of that value with the other fields. Here’s how we can define this structure:
Structure IntegerTypes ' A 64-bit integer Dim Long0 As Long ' Two 32-bit integers Dim Integer0 As Integer Dim Integer1 As Integer ' Four 16-bit integers Dim Short0 As Short Dim Short1 As Short Dim Short2 As Short Dim Short3 As Short ' Eight 8-bit integers Dim Byte0 As Byte Dim Byte1 As Byte Dim Byte2 As Byte Dim Byte3 As Byte Dim Byte4 As Byte Dim Byte5 As Byte Dim Byte6 As Byte Dim Byte7 As Byte ' Low byte of a word Function LowByte(ByVal Value As Long) As Byte Long0 = Value Return Byte0 End Function ' High byte of a word Function HighByte(ByVal Value As Long) As Byte Long0 = Value Return Byte1 End Function ' Low word of a doubleword Function LowWord(ByVal Value As Long) As Short Long0 = Value Return Short0 End Function ' High word of a doubleword Function HighWord(ByVal Value As Long) As Short Long0 = Value Return Short1 End FunctionEnd Structure Here’s how you can test the IntegerTypes structure to retrieve the hi/low byte/word of a value, and to do other operations:
Dim it As IntegerTypesit.Short0 = 517 ' hex 0205Console.WriteLine(it.Byte0) ' => 5Console.WriteLine(it.Byte1) ' => 2Console.WriteLine(it.LowByte(517)) ' => 5Console.WriteLine(it.HighByte(517)) ' => 2Console.WriteLine(it.LowWord(&HFFFF1000)) ' => 4096Console.WriteLine(it.HighWord(&HFFFF1000)) ' => -1————————–
Note: this code is taken from Francesco Balena’s Programming Microsoft Visual Basic .NET book (MS Press 2002)
