Sign extend 16-bit value to Integer

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  • Jack Jackson
    #1

    Sign extend 16-bit value to Integer

    What is the best way to sign extend a 16-bit value (such as half of
    the lparam value in WM_NCxxx messages) into an Integer?

    Currently I test for the 8000 bit and if set OR in FFFF0000, but it
    seems like there should be some built-in way to do this.
    Tags: None
    • James Hahn
      #2
      Re: Sign extend 16-bit value to Integer

      If it's a Short (Int16) it will widen correctly to Integer (Int32).

      "Jack Jackson" <jjackson@cinno vations.netwrot e in message
      news:st6ge457od qs45sbrs005u6b3 5ba4j7t8q@4ax.c om...
      What is the best way to sign extend a 16-bit value (such as half of
      the lparam value in WM_NCxxx messages) into an Integer?
      >
      Currently I test for the 8000 bit and if set OR in FFFF0000, but it
      seems like there should be some built-in way to do this.

        Comment

        • Family Tree Mike
          #3
          Re: Sign extend 16-bit value to Integer

          Try the following example for BitConverter to see if this works for you.

          Sub Main()
          Dim x32 As Int32 = &H432312AF
          Dim a16, b16 As Int16 ' if you want 2 byte ints
          Dim a32, b32 As Int32 ' if you want 4 byte ints
          Dim ba As Byte() = BitConverter.Ge tBytes(x32)

          a16 = BitConverter.To Int16(ba, 0)
          b16 = BitConverter.To Int16(ba, 2)

          a32 = a16 : b32 = b16

          Console.Out.Wri teLine(String.F ormat("{0:x} {1:x} {2:x}", x32, a32, b32))
          Console.In.Read Line()

          End Sub

          "Jack Jackson" <jjackson@cinno vations.netwrot e in message
          news:st6ge457od qs45sbrs005u6b3 5ba4j7t8q@4ax.c om...
          What is the best way to sign extend a 16-bit value (such as half of
          the lparam value in WM_NCxxx messages) into an Integer?
          >
          Currently I test for the 8000 bit and if set OR in FFFF0000, but it
          seems like there should be some built-in way to do this.

            Comment

            • Jack Jackson
              #4
              Re: Sign extend 16-bit value to Integer

              Thanks, that works fine.

              On Sun, 5 Oct 2008 16:53:34 -0400, "Family Tree Mike"
              <FamilyTreeMike @ThisOldHouse.c omwrote:
              >Try the following example for BitConverter to see if this works for you.
              >
              Sub Main()
              Dim x32 As Int32 = &H432312AF
              Dim a16, b16 As Int16 ' if you want 2 byte ints
              Dim a32, b32 As Int32 ' if you want 4 byte ints
              Dim ba As Byte() = BitConverter.Ge tBytes(x32)
              >
              a16 = BitConverter.To Int16(ba, 0)
              b16 = BitConverter.To Int16(ba, 2)
              >
              a32 = a16 : b32 = b16
              >
              Console.Out.Wri teLine(String.F ormat("{0:x} {1:x} {2:x}", x32, a32, b32))
              Console.In.Read Line()
              >
              End Sub
              >
              >"Jack Jackson" <jjackson@cinno vations.netwrot e in message
              >news:st6ge457o dqs45sbrs005u6b 35ba4j7t8q@4ax. com...
              >What is the best way to sign extend a 16-bit value (such as half of
              >the lparam value in WM_NCxxx messages) into an Integer?
              >>
              >Currently I test for the 8000 bit and if set OR in FFFF0000, but it
              >seems like there should be some built-in way to do this.

                Comment

                • Cor Ligthert
                  #5
                  Re: Sign extend 16-bit value to Integer

                  Jack,

                  Copied from a message in this newsgroup from Tom Spink

                  \\\
                  Dim strText = "The String Being Measured"
                  Dim g As Graphics = Me.CreateGraphi cs
                  Dim sfSize As SizeF = g.MeasureString (strText, Me.Font)

                  MsgBox("Width: " & sfSize.Width & vbCrLf & "Height: " & sfSize.Height)
                  ///

                  Cor

                  "Jack Jackson" <jjackson@cinno vations.netschr eef in bericht
                  news:st6ge457od qs45sbrs005u6b3 5ba4j7t8q@4ax.c om...
                  What is the best way to sign extend a 16-bit value (such as half of
                  the lparam value in WM_NCxxx messages) into an Integer?
                  >
                  Currently I test for the 8000 bit and if set OR in FFFF0000, but it
                  seems like there should be some built-in way to do this.

                    Comment

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