VB6中的LSet语句和RSet语句详解

[Let] varname = expression

LSet Statement

Left aligns a string within a string variable, or copies a variable of one user-defined type to another variable of a different user-defined type.

RSet Statement

Right aligns a string within a string variable.

Sub Main()
    Dim url As String
    Dim s As String
   
    Let url = "https://www.jb51.net"
    s = String$(20, "*")
   
    LSet s = url
    Debug.Print s
   
    RSet s = url
    Debug.Print s
End Sub

https://www.jb51.net    

     https://www.jb51.net

Sub Main()
    Debug.Print IPToLong("61.135.169.125")
End Sub

Private Function IPToLong(IPStr As String) As Long
   Dim Str() As String, HEXStr As String, TempStr As String
   Dim x As Long
  
   Str = Split(IPStr, ".")
   HEXStr = ""
   For x = 0 To UBound(Str)
      TempStr = Hex(Str(x))
      HEXStr = HEXStr & String(2 - Len(TempStr), "0") & TempStr
   Next x
   IPToLong = CLng("&H" & HEXStr)
End Function

Private Type myBytes
    B1 As Byte
    B2 As Byte
    B3 As Byte
    B4 As Byte
End Type

Private Type myLong
    Val As Long
End Type

'By Demon
'http://jb51.net

Public Function IP2Long(ip As String) As Long
    Dim a() As String
    Dim b As myBytes
    Dim l As myLong
   
    a = Split(ip, ".")
    '注意Little-Endian
    b.B1 = CByte(a(3))
    b.B2 = CByte(a(2))
    b.B3 = CByte(a(1))
    b.B4 = CByte(a(0))
    LSet l = b
    IP2Long = l.Val
End Function

00401A0E   lea     eax, dword ptr [ebp-0x20]   ; 变量b的地址
00401A11   push    eax
00401A12   lea     eax, dword ptr [ebp-0x14]   ; 变量l的地址
00401A15   push    eax
00401A16   push    0x4
00401A18   call    __vbaCopyBytes              ;  jmp to MSVBVM60.__vbaCopyBytes

72A1A0F3 >  mov     ecx, dword ptr [esp+0x4]
72A1A0F7    push    esi
72A1A0F8    mov     esi, dword ptr [esp+0x10]
72A1A0FC    push    edi
72A1A0FD    mov     edi, dword ptr [esp+0x10]
72A1A101    mov     eax, ecx
72A1A103    mov     edx, edi
72A1A105    shr     ecx, 0x2
72A1A108    rep     movs dword ptr es:[edi], dword ptr [esi]
72A1A10A    mov     ecx, eax
72A1A10C    mov     eax, edx
72A1A10E    and     ecx, 0x3
72A1A111    rep     movs byte ptr es:[edi], byte ptr [esi]
72A1A113    pop     edi
72A1A114    pop     esi
72A1A115    retn    0xC

Warning   Using LSet to copy a variable of one user-defined type into a variable of a different user-defined type is not recommended. Copying data of one data type into space reserved for a different data type can cause unpredictable results.

When you copy a variable from one user-defined type to another, the binary data from one variable is copied into the memory space of the other, without regard for the data types specified for the elements.