win32: Add implementation of pthread_once

This function will be required to make dav1d_init threadsafe.

Full erro checking support is included in this implementation,
for completeness, even though dav1d_init cannot fail, and thus
will ignore the return value of pthread_once.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/win32/thread.c b/src/win32/thread.c
index c73dba1..41a04e5 100644
--- a/src/win32/thread.c
+++ b/src/win32/thread.c
@@ -125,4 +125,23 @@ void pthread_join(pthread_t thread, void** res)
     free(th);
 }
 
+int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+    BOOL fPending = FALSE;
+    BOOL fStatus;
+
+    fStatus = InitOnceBeginInitialize(once_control, 0, &fPending, NULL);
+    if (fStatus != TRUE)
+        return EINVAL;
+
+    if (fPending == TRUE)
+        init_routine();
+
+    fStatus = InitOnceComplete(once_control, 0, NULL);
+    if (!fStatus)
+        return EINVAL;
+
+    return 0;
+}
+
 #endif