Binaryworld - Retrieving the hi/low byte/word of a value, and other operations ... [ VB.net -> Language ]

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:

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<StructLayout(LayoutKind.Explicit)> Structure IntegerTypes
  ' A 64-bit integer
  <FieldOffset(0)> Dim Long0 As Long
  ' Two 32-bit integers
  <FieldOffset(0)> Dim Integer0 As Integer
  <FieldOffset(4)> Dim Integer1 As Integer
  ' Four 16-bit integers
  <FieldOffset(0)> Dim Short0 As Short
  <FieldOffset(2)> Dim Short1 As Short
  <FieldOffset(4)> Dim Short2 As Short
  <FieldOffset(6)> Dim Short3 As Short
  ' Eight 8-bit integers
  <FieldOffset(0)> Dim Byte0 As Byte
  <FieldOffset(1)> Dim Byte1 As Byte
  <FieldOffset(2)> Dim Byte2 As Byte
  <FieldOffset(3)> Dim Byte3 As Byte
  <FieldOffset(4)> Dim Byte4 As Byte
  <FieldOffset(5)> Dim Byte5 As Byte
  <FieldOffset(6)> Dim Byte6 As Byte
  <FieldOffset(7)> 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 Function

End 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:

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Dim it As IntegerTypes

it.Short0 = 517         ' hex 0205
Console.WriteLine(it.Byte0)    ' => 5
Console.WriteLine(it.Byte1)    ' => 2

Console.WriteLine(it.LowByte(517))      ' => 5
Console.WriteLine(it.HighByte(517))     ' => 2
Console.WriteLine(it.LowWord(&HFFFF1000))  ' => 4096
Console.WriteLine(it.HighWord(&HFFFF1000)) ' => -1