为什么我的Short在VB.net中包含4个字节

Question

根据MSDN,Short数据类型由两个字节组成:https://msdn.microsoft.com/en-us/library/47zceaw7.aspx

但是如果我定义一个Short变量,内容总是4个字节:&HFFFFFFFF

Dim crc As Short = CShort(&HFFFFS) ' crc = &HFFFFFFFF
Dim crc As Short = &HFFFFS         ' crc = &HFFFFFFFF

这句话甚至给我一个错误:

Dim crc As Short = CShort(&HFFFF) ' Error: Constant expression not representable in type 'Short'

这有什么用？为什么我Short不占用两个字节？

MWE补充道:

Public Function CRC16(ByVal dataFrame As Byte(), ByVal dataLength As Int16) As Int16

    Dim index As Int16
    Dim crc As Short = &HFFFFS

    For iCount As Int16 = 0 To CShort(dataLength - 1)
        index = (crc >> 8) Xor dataFrame(iCount)
        crc = CShort(&HFFFF And ((crc << 8) Xor CRC_Table(index)))
    Next

    Return crc

End Function

Answer 1

这是因为a Short是有符号的,所以最重要的位是为符号保留的.因此,您可以在签名的短片中存储的最高值是&H7FFF或Int16.MaxValue

如果你想利用所有16​​位,那么你需要使用Unsigned Short(UInt16)

所以这个失败:

Dim crc As Short = CShort(&HFFFF) 

但是这个作品:

Dim crc As UShort = CUShort(&HFFFF)