compat/win32/lazyload.h

   1 #ifndef LAZYLOAD_H
   2 #define LAZYLOAD_H
   3
   4 /*
   5  * A pair of macros to simplify loading of DLL functions. Example:
   6  *
   7  *   DECLARE_PROC_ADDR(kernel32.dll, BOOL, WINAPI, CreateHardLinkW,
   8  *                     LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
   9  *
  10  *   if (!INIT_PROC_ADDR(CreateHardLinkW))
  11  *           return error("Could not find CreateHardLinkW() function";
  12  *
  13  *   if (!CreateHardLinkW(source, target, NULL))
  14  *           return error("could not create hardlink from %S to %S",
  15  *                        source, target);
  16  */
  17
  18 typedef void (*FARVOIDPROC)(void);
  19
  20 struct proc_addr {
  21         const char *const dll;
  22         const char *const function;
  23         FARVOIDPROC pfunction;
  24         unsigned initialized : 1;
  25 };
  26
  27 /* Declares a function to be loaded dynamically from a DLL. */
  28 #define DECLARE_PROC_ADDR(dll, rettype, convention, function, ...) \
  29         static struct proc_addr proc_addr_##function = \
  30         { #dll, #function, NULL, 0 }; \
  31         typedef rettype (convention *proc_type_##function)(__VA_ARGS__); \
  32         static proc_type_##function function
  33
  34 /*
  35  * Loads a function from a DLL (once-only).
  36  * Returns non-NULL function pointer on success.
  37  * Returns NULL + errno == ENOSYS on failure.
  38  * This function is not thread-safe.
  39  */
  40 #define INIT_PROC_ADDR(function) \
  41         (function = (proc_type_##function)get_proc_addr(&proc_addr_##function))
  42
  43 static inline FARVOIDPROC get_proc_addr(struct proc_addr *proc)
  44 {
  45         /* only do this once */
  46         if (!proc->initialized) {
  47                 HANDLE hnd;
  48                 proc->initialized = 1;
  49                 hnd = LoadLibraryExA(proc->dll, NULL,
  50                                      LOAD_LIBRARY_SEARCH_SYSTEM32);
  51                 if (hnd)
  52                         proc->pfunction = (FARVOIDPROC)GetProcAddress(hnd,
  53                                                         proc->function);
  54         }
  55         /* set ENOSYS if DLL or function was not found */
  56         if (!proc->pfunction)
  57                 errno = ENOSYS;
  58         return proc->pfunction;
  59 }
  60
  61 #endif