VB6 – 使用指针声明和调用C DLL

我有一个旧的C DLL，我用来从Ruby调用，但现在我需要从VB6调用它，我无法弄清楚这样做的正确方法。

这是我需要的function的标题：

int Decrunch(const BYTE *src, BYTE *dest, DWORD src_length)

* src是一个字节序列，将由函数解密

* dest是一个缓冲区，它将接收解密的数据。 我可以使用dest = NULL调用该函数，它将返回解密数据的大小，因此我可以使用它来创建具有正确大小的缓冲区。

我试图用src和dest声明它作为字符串（就像我在Ruby中做的那样）但是它不起作用。 我也尝试将它们声明为Byte并传递一个字节数组的第一个元素，正如我在一些教程中指出的那样，但我认为我没有正确地做到这一点。

有人可以帮我弄这个吗？

谢谢！

Answer 1

空气代码

 Private Declare DecrunchGetLength Alias "Decrunch" Lib "somedll.DLL" (ByRef src As Byte, ByVal nullptr As Long, ByVal SrcLength As Long) As Long Private Declare Decrunch Alias "Decrunch" Lib "somedll.DLL" (ByRef src As Byte, ByRef dest As Byte, ByVal SrcLength As Long) As Long Dim destLen As Long Dim src(0 To 9) As Byte Dim dest() As Byte ' get bytes into src somehow ' get dest length destLen = DecrunchGetLen( src(0), 0, 10) ReDim dest(0 To destLen - 1) destLen = Decrunch( src(0), dest(0), 10) 

有用的链接

• 声明声明
• 从VB5 / VB6 高级 调用C DLL

Answer 2

您可以像这样使用CDECL调用thunk

 Option Explicit '--- for VirtualProtect' Private Const PAGE_EXECUTE_READWRITE As Long = &H40 Private Declare Function VirtualProtect Lib "kernel32" (lpAddress As Any, ByVal dwSize As Long, ByVal flNewProtect As Long, lpflOldProtect As Long) As Long Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long Private Declare Function GetProcAddress Lib "kernel32" (ByVal hModule As Long, ByVal lpProcName As String) As Long Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long Private Const STR_MYDLL As String = "my.dll" Private Type UcsParamThunk pfn As Long Call_(0 To 7) As Long End Type Private m_hModule As Long Private m_uCallThunk As UcsParamThunk Private Sub Form_Load() Dim baSrc() As Byte Dim baDst() As Byte On Error GoTo EH ReDim baSrc(0 To 10000) As Byte ReDim baDst(0 To 20000) As Byte pvCallFunc "Decrunch", VarPtr(baSrc(0)), VarPtr(baDst(0)), UBound(baSrc) + 1 Exit Sub EH: MsgBox Error$, vbCritical End Sub Private Function pvCallFunc(sFunc As String, ParamArray A()) As Long Dim pfn As Long Dim lIdx As Long Dim aParams() As Long If m_hModule = 0 Then m_hModule = LoadLibrary(STR_MYDLL) If m_hModule = 0 Then Err.Raise vbObjectError, , STR_MYDLL & " not found" End If pvInitCallCdeclThunk m_uCallThunk End If pfn = GetProcAddress(m_hModule, sFunc) If pfn = 0 Then Err.Raise vbObjectError, , "Export not found: " & sFunc End If ReDim aParams(0 To UBound(A) + 1) As Long For lIdx = 0 To UBound(A) aParams(lIdx) = CLng(A(lIdx)) Next pvCallFunc = CallWindowProc(m_uCallThunk.pfn, pfn, UBound(aParams), VarPtr(aParams(0)), 0) End Function Private Sub pvInitCallCdeclThunk(Thunk As UcsParamThunk) 'void _stdcall thunk(int pfn, int count, int args, int dummy) ' push ebp ' mov ebp, esp ' mov ecx, count ' jecxz _skip_params ' mov edx, args '_params_loop: ' push dword ptr [edx + ecx * 4 - 4] ' loop _params_loop '_skip_params: ' call pfn ' mov esp,ebp ' pop ebp ' ret 10h ' nop ' nop With Thunk .Call_(0) = &H8BEC8B55 .Call_(1) = &H9E30C4D .Call_(2) = &HFF10558B .Call_(3) = &HE2FC8A74 .Call_(4) = &H855FFFA .Call_(5) = &HC25DE58B .Call_(6) = &H90900010 .pfn = VarPtr(.Call_(0)) Call VirtualProtect(Thunk, Len(Thunk), PAGE_EXECUTE_READWRITE, 0) End With End Sub