如何转换C代码中的高字和低字
出处：网络

HiWords and LoWords from Long Values

　When translating C code to VB, you quite often come across the HiWord and LoWord

operators, used to pack two integers into a long value. A simple translation of

HiWord code will run into difficulties when unsigned integer arithmetic is being

used in the C code and the highest bit of the long value can be set. Since VB doesn't

support unsigned arithmetic we have to strip out the high bit and add it back again

later to avoid overflows and misleading results.

　　当把C代码翻译到VB时，你经常会遇到高字和低字的操作，通常是把两个整型值合成一个长整型。当在C代码中使用了无符号整型，这最高一位是可以被设置的，因此简单的直接转换高字将会遇到困难。由于VB不支持无符号算术符，我们只好剥去这最高一位，在稍后再把它加回来，以避免溢出和错误的结果。（WXJ_Lake 译）

开始一个新工程，增添一个标准模块。把以下代码写入模块：

Start a new project then add a module. Add the following code to the module:

Public Property Get LoWord(ByRef lThis As Long) As Long

　 LoWord = (lThis And &HFFFF&)

End Property

Public Property Let LoWord(ByRef lThis As Long, ByVal lLoWord As Long)

　 lThis = lThis And Not &HFFFF& Or lLoWord

End Property

Public Property Get HiWord(ByRef lThis As Long) As Long

　 If (lThis And &H80000000) = &H80000000 Then

　　　HiWord = ((lThis And &H7FFF0000) \ &H10000) Or &H8000&

　 Else

　　　HiWord = (lThis And &HFFFF0000) \ &H10000

　 End If

End Property

Public Property Let HiWord(ByRef lThis As Long, ByVal lHiWord As Long)

　 If (lHiWord And &H8000&) = &H8000& Then

　　　lThis = lThis And Not &HFFFF0000 Or ((lHiWord And &H7FFF&) * &H10000) Or &H80000000

　 Else

　　　lThis = lThis And Not &HFFFF0000 Or (lHiWord * &H10000)

　 End If

End Property

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