'标准的做法SwapStr Sub SwapStr(sA As String, sB As String) Dim
sTmp As String sTmp = sA: sA = sB: sB = sTmp End
Sub 【程序二】:
'用指针的做法SwapPtr Private Declare Sub CopyMemory Lib "kernel32" Alias
"RtlMoveMemory" _ (Destination As Any, Source As Any, ByVal Length As
Long)
Sub SwapPtr(sA As String, sB As String) Dim lTmp As
Long CopyMemory lTmp, ByVal VarPtr(sA), 4 CopyMemory ByVal
VarPtr(sA), ByVal VarPtr(sB), 4 CopyMemory ByVal VarPtr(sB), lTmp,
4 End
Sub 你是不是以为第一个程序要快,因为它看着简单而且不用调用API(调用API需要额外的处理,VB文档明确指出大量调用API将降低程序性能)。但事实上,在VB集成环境中运行,程序二要比程序一快四分之一;而编译成本机代码或p-code,程序二基本上要比程序一快一倍。下面是两个函数在编译成本机代码后,运行不同次数所花时间的比较: