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#ifndef LAZYLOAD_H
#define LAZYLOAD_H
/*
* A pair of macros to simplify loading of DLL functions. Example:
*
* DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
* LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
*
* if (!INIT_PROC_ADDR(CreateHardLinkW))
* return error("Could not find CreateHardLinkW() function";
*
* if (!CreateHardLinkW(source, target, NULL))
* return error("could not create hardlink from %S to %S",
* source, target);
*/
typedef void (*FARVOIDPROC)(void);
struct proc_addr {
const char *const dll;
const char *const function;
FARVOIDPROC pfunction;
unsigned initialized : 1;
};
/* Declares a function to be loaded dynamically from a DLL. */
#define DECLARE_PROC_ADDR(dll, rettype, function, ...) \
static struct proc_addr proc_addr_##function = \
{ #dll, #function, NULL, 0 }; \
typedef rettype (WINAPI *proc_type_##function)(__VA_ARGS__); \
static proc_type_##function function
/*
* Loads a function from a DLL (once-only).
* Returns non-NULL function pointer on success.
* Returns NULL + errno == ENOSYS on failure.
* This function is not thread-safe.
*/
#define INIT_PROC_ADDR(function) \
(function = (proc_type_##function)get_proc_addr(&proc_addr_##function))
static inline FARVOIDPROC get_proc_addr(struct proc_addr *proc)
{
/* only do this once */
if (!proc->initialized) {
HANDLE hnd;
proc->initialized = 1;
hnd = LoadLibraryExA(proc->dll, NULL,
LOAD_LIBRARY_SEARCH_SYSTEM32);
if (hnd)
proc->pfunction = (FARVOIDPROC)GetProcAddress(hnd,
proc->function);
}
/* set ENOSYS if DLL or function was not found */
if (!proc->pfunction)
errno = ENOSYS;
return proc->pfunction;
}
#endif
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