w32pthreads: Load dynamically loaded functions on demand
[ffmpeg.git] / compat / w32pthreads.h
index f8eb0c8..ac9a814 100644 (file)
@@ -64,28 +64,7 @@ typedef struct pthread_cond_t {
 } pthread_cond_t;
 #endif
 
-/* function pointers to conditional variable API on windows 6.0+ kernels */
-#if _WIN32_WINNT < 0x0600
-static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
-static void (WINAPI *cond_init)(pthread_cond_t *cond);
-static void (WINAPI *cond_signal)(pthread_cond_t *cond);
-static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
-                                DWORD milliseconds);
-#else
-#define cond_init      InitializeConditionVariable
-#define cond_broadcast WakeAllConditionVariable
-#define cond_signal    WakeConditionVariable
-#define cond_wait      SleepConditionVariableCS
-
-#define CreateEvent(a, reset, init, name)                   \
-    CreateEventEx(a, name,                                  \
-                  (reset ? CREATE_EVENT_MANUAL_RESET : 0) | \
-                  (init ? CREATE_EVENT_INITIAL_SET : 0),    \
-                  EVENT_ALL_ACCESS)
-// CreateSemaphoreExA seems to be desktop-only, but as long as we don't
-// use named semaphores, it doesn't matter if we use the W version.
-#define CreateSemaphore(a, b, c, d) \
-    CreateSemaphoreExW(a, b, c, d, 0, SEMAPHORE_ALL_ACCESS)
+#if _WIN32_WINNT >= 0x0600
 #define InitializeCriticalSection(x) InitializeCriticalSectionEx(x, 0, 0)
 #define WaitForSingleObject(a, b) WaitForSingleObjectEx(a, b, FALSE)
 #endif
@@ -138,8 +117,113 @@ static inline int pthread_mutex_unlock(pthread_mutex_t *m)
     return 0;
 }
 
+#if _WIN32_WINNT >= 0x0600
+
+typedef INIT_ONCE pthread_once_t;
+#define PTHREAD_ONCE_INIT INIT_ONCE_STATIC_INIT
+
+static av_unused int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+    BOOL pending = FALSE;
+    InitOnceBeginInitialize(once_control, 0, &pending, NULL);
+    if (pending)
+        init_routine();
+    InitOnceComplete(once_control, 0, NULL);
+    return 0;
+}
+
+static inline void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
+{
+    InitializeConditionVariable(cond);
+}
+
+/* native condition variables do not destroy */
+static inline void pthread_cond_destroy(pthread_cond_t *cond)
+{
+    return;
+}
+
+static inline void pthread_cond_broadcast(pthread_cond_t *cond)
+{
+    WakeAllConditionVariable(cond);
+}
+
+static inline int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
+{
+    SleepConditionVariableCS(cond, mutex, INFINITE);
+    return 0;
+}
+
+static inline void pthread_cond_signal(pthread_cond_t *cond)
+{
+    WakeConditionVariable(cond);
+}
+
+#else // _WIN32_WINNT < 0x0600
+
+/* atomic init state of dynamically loaded functions */
+static LONG w32thread_init_state = 0;
+static av_unused void w32thread_init(void);
+
+/* for pre-Windows 6.0 platforms, define INIT_ONCE struct,
+ * compatible to the one used in the native API */
+
+typedef union pthread_once_t  {
+    void * Ptr;    ///< For the Windows 6.0+ native functions
+    LONG state;    ///< For the pre-Windows 6.0 compat code
+} pthread_once_t;
+
+#define PTHREAD_ONCE_INIT {0}
+
+/* function pointers to init once API on windows 6.0+ kernels */
+static BOOL (WINAPI *initonce_begin)(pthread_once_t *lpInitOnce, DWORD dwFlags, BOOL *fPending, void **lpContext);
+static BOOL (WINAPI *initonce_complete)(pthread_once_t *lpInitOnce, DWORD dwFlags, void *lpContext);
+
+/* pre-Windows 6.0 compat using a spin-lock */
+static inline void w32thread_once_fallback(LONG volatile *state, void (*init_routine)(void))
+{
+    switch (InterlockedCompareExchange(state, 1, 0)) {
+    /* Initial run */
+    case 0:
+        init_routine();
+        InterlockedExchange(state, 2);
+        break;
+    /* Another thread is running init */
+    case 1:
+        while (1) {
+            MemoryBarrier();
+            if (*state == 2)
+                break;
+            Sleep(0);
+        }
+        break;
+    /* Initialization complete */
+    case 2:
+        break;
+    }
+}
+
+static av_unused int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+    w32thread_once_fallback(&w32thread_init_state, w32thread_init);
+
+    /* Use native functions on Windows 6.0+ */
+    if (initonce_begin && initonce_complete) {
+        BOOL pending = FALSE;
+        initonce_begin(once_control, 0, &pending, NULL);
+        if (pending)
+            init_routine();
+        initonce_complete(once_control, 0, NULL);
+        return 0;
+    }
+
+    w32thread_once_fallback(&once_control->state, init_routine);
+    return 0;
+}
+
 /* for pre-Windows 6.0 platforms we need to define and use our own condition
  * variable and api */
+
 typedef struct  win32_cond_t {
     pthread_mutex_t mtx_broadcast;
     pthread_mutex_t mtx_waiter_count;
@@ -149,9 +233,19 @@ typedef struct  win32_cond_t {
     volatile int is_broadcast;
 } win32_cond_t;
 
+/* function pointers to conditional variable API on windows 6.0+ kernels */
+static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
+static void (WINAPI *cond_init)(pthread_cond_t *cond);
+static void (WINAPI *cond_signal)(pthread_cond_t *cond);
+static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
+                                DWORD milliseconds);
+
 static av_unused void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
 {
     win32_cond_t *win32_cond = NULL;
+
+    w32thread_once_fallback(&w32thread_init_state, w32thread_init);
+
     if (cond_init) {
         cond_init(cond);
         return;
@@ -276,6 +370,7 @@ static av_unused void pthread_cond_signal(pthread_cond_t *cond)
 
     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
 }
+#endif
 
 static av_unused void w32thread_init(void)
 {
@@ -290,6 +385,10 @@ static av_unused void w32thread_init(void)
         (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
     cond_wait      =
         (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
+    initonce_begin =
+        (void*)GetProcAddress(kernel_dll, "InitOnceBeginInitialize");
+    initonce_complete =
+        (void*)GetProcAddress(kernel_dll, "InitOnceComplete");
 #endif
 
 }