Andrew's git - gitweb.git/blob - 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, 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
  18struct proc_addr {
  19        const char *const dll;
  20        const char *const function;
  21        FARPROC pfunction;
  22        unsigned initialized : 1;
  23};
  24
  25/* Declares a function to be loaded dynamically from a DLL. */
  26#define DECLARE_PROC_ADDR(dll, rettype, function, ...) \
  27        static struct proc_addr proc_addr_##function = \
  28        { #dll, #function, NULL, 0 }; \
  29        static rettype (WINAPI *function)(__VA_ARGS__)
  30
  31/*
  32 * Loads a function from a DLL (once-only).
  33 * Returns non-NULL function pointer on success.
  34 * Returns NULL + errno == ENOSYS on failure.
  35 * This function is not thread-safe.
  36 */
  37#define INIT_PROC_ADDR(function) \
  38        (function = get_proc_addr(&proc_addr_##function))
  39
  40static inline void *get_proc_addr(struct proc_addr *proc)
  41{
  42        /* only do this once */
  43        if (!proc->initialized) {
  44                HANDLE hnd;
  45                proc->initialized = 1;
  46                hnd = LoadLibraryExA(proc->dll, NULL,
  47                                     LOAD_LIBRARY_SEARCH_SYSTEM32);
  48                if (hnd)
  49                        proc->pfunction = GetProcAddress(hnd, proc->function);
  50        }
  51        /* set ENOSYS if DLL or function was not found */
  52        if (!proc->pfunction)
  53                errno = ENOSYS;
  54        return proc->pfunction;
  55}
  56
  57#endif