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      1 /*
      2 
      3 Entry point for the Windows NT DLL.
      4 
      5 About the only reason for having this, is so initall() can automatically
      6 be called, removing that burden (and possible source of frustration if
      7 forgotten) from the programmer.
      8 
      9 */
     10 
     11 #include "Python.h"
     12 #include "windows.h"
     13 
     14 #ifdef Py_ENABLE_SHARED
     15 char dllVersionBuffer[16] = ""; // a private buffer
     16 
     17 // Python Globals
     18 HMODULE PyWin_DLLhModule = NULL;
     19 const char *PyWin_DLLVersionString = dllVersionBuffer;
     20 
     21 // Windows "Activation Context" work:
     22 // Our .pyd extension modules are generally built without a manifest (ie,
     23 // those included with Python and those built with a default distutils.
     24 // This requires we perform some "activation context" magic when loading our
     25 // extensions.  In summary:
     26 // * As our DLL loads we save the context being used.
     27 // * Before loading our extensions we re-activate our saved context.
     28 // * After extension load is complete we restore the old context.
     29 // As an added complication, this magic only works on XP or later - we simply
     30 // use the existence (or not) of the relevant function pointers from kernel32.
     31 // See bug 4566 (http://python.org/sf/4566) for more details.
     32 
     33 typedef BOOL (WINAPI * PFN_GETCURRENTACTCTX)(HANDLE *);
     34 typedef BOOL (WINAPI * PFN_ACTIVATEACTCTX)(HANDLE, ULONG_PTR *);
     35 typedef BOOL (WINAPI * PFN_DEACTIVATEACTCTX)(DWORD, ULONG_PTR);
     36 typedef BOOL (WINAPI * PFN_ADDREFACTCTX)(HANDLE);
     37 typedef BOOL (WINAPI * PFN_RELEASEACTCTX)(HANDLE);
     38 
     39 // locals and function pointers for this activation context magic.
     40 static HANDLE PyWin_DLLhActivationContext = NULL; // one day it might be public
     41 static PFN_GETCURRENTACTCTX pfnGetCurrentActCtx = NULL;
     42 static PFN_ACTIVATEACTCTX pfnActivateActCtx = NULL;
     43 static PFN_DEACTIVATEACTCTX pfnDeactivateActCtx = NULL;
     44 static PFN_ADDREFACTCTX pfnAddRefActCtx = NULL;
     45 static PFN_RELEASEACTCTX pfnReleaseActCtx = NULL;
     46 
     47 void _LoadActCtxPointers()
     48 {
     49     HINSTANCE hKernel32 = GetModuleHandleW(L"kernel32.dll");
     50     if (hKernel32)
     51         pfnGetCurrentActCtx = (PFN_GETCURRENTACTCTX) GetProcAddress(hKernel32, "GetCurrentActCtx");
     52     // If we can't load GetCurrentActCtx (ie, pre XP) , don't bother with the rest.
     53     if (pfnGetCurrentActCtx) {
     54         pfnActivateActCtx = (PFN_ACTIVATEACTCTX) GetProcAddress(hKernel32, "ActivateActCtx");
     55         pfnDeactivateActCtx = (PFN_DEACTIVATEACTCTX) GetProcAddress(hKernel32, "DeactivateActCtx");
     56         pfnAddRefActCtx = (PFN_ADDREFACTCTX) GetProcAddress(hKernel32, "AddRefActCtx");
     57         pfnReleaseActCtx = (PFN_RELEASEACTCTX) GetProcAddress(hKernel32, "ReleaseActCtx");
     58     }
     59 }
     60 
     61 ULONG_PTR _Py_ActivateActCtx()
     62 {
     63     ULONG_PTR ret = 0;
     64     if (PyWin_DLLhActivationContext && pfnActivateActCtx)
     65         if (!(*pfnActivateActCtx)(PyWin_DLLhActivationContext, &ret)) {
     66             OutputDebugString("Python failed to activate the activation context before loading a DLL\n");
     67             ret = 0; // no promise the failing function didn't change it!
     68         }
     69     return ret;
     70 }
     71 
     72 void _Py_DeactivateActCtx(ULONG_PTR cookie)
     73 {
     74     if (cookie && pfnDeactivateActCtx)
     75         if (!(*pfnDeactivateActCtx)(0, cookie))
     76             OutputDebugString("Python failed to de-activate the activation context\n");
     77 }
     78 
     79 BOOL    WINAPI  DllMain (HANDLE hInst,
     80                                                 ULONG ul_reason_for_call,
     81                                                 LPVOID lpReserved)
     82 {
     83     switch (ul_reason_for_call)
     84     {
     85         case DLL_PROCESS_ATTACH:
     86             PyWin_DLLhModule = hInst;
     87             // 1000 is a magic number I picked out of the air.  Could do with a #define, I spose...
     88             LoadString(hInst, 1000, dllVersionBuffer, sizeof(dllVersionBuffer));
     89 
     90             // and capture our activation context for use when loading extensions.
     91             _LoadActCtxPointers();
     92             if (pfnGetCurrentActCtx && pfnAddRefActCtx)
     93                 if ((*pfnGetCurrentActCtx)(&PyWin_DLLhActivationContext))
     94                     if (!(*pfnAddRefActCtx)(PyWin_DLLhActivationContext))
     95                         OutputDebugString("Python failed to load the default activation context\n");
     96             break;
     97 
     98         case DLL_PROCESS_DETACH:
     99             if (pfnReleaseActCtx)
    100                 (*pfnReleaseActCtx)(PyWin_DLLhActivationContext);
    101             break;
    102     }
    103     return TRUE;
    104 }
    105 
    106 #endif /* Py_ENABLE_SHARED */
    107