win: simplify uv_once implementation

* win: simplify uv_once implementation

InitOnceExecuteOnce is available in Windows >= Vista.

Ref: https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initonceexecuteonce

1 files changed, 11 insertions, 33 deletions

diff --git a/src/win/thread.c b/src/win/thread.c
index 57c25e8f..bf39b886 100644
--- a/src/win/thread.c
+++ b/src/win/thread.c
@@ -32,45 +32,23 @@
 #include "uv.h"
 #include "internal.h"
 
-static void uv__once_inner(uv_once_t* guard, void (*callback)(void)) {
-  DWORD result;
-  HANDLE existing_event, created_event;
-
-  created_event = CreateEvent(NULL, 1, 0, NULL);
-  if (created_event == 0) {
-    /* Could fail in a low-memory situation? */
-    uv_fatal_error(GetLastError(), "CreateEvent");
-  }
+typedef void (*uv__once_cb)(void);
 
-  existing_event = InterlockedCompareExchangePointer(&guard->event,
-                                                     created_event,
-                                                     NULL);
+typedef struct {
+  uv__once_cb callback;
+} uv__once_data_t;
 
-  if (existing_event == NULL) {
-    /* We won the race */
-    callback();
+static BOOL WINAPI uv__once_inner(INIT_ONCE *once, void* param, void** context) {
+  uv__once_data_t* data = param;
 
-    result = SetEvent(created_event);
-    assert(result);
-    guard->ran = 1;
+  data->callback();
 
-  } else {
-    /* We lost the race. Destroy the event we created and wait for the existing
-     * one to become signaled. */
-    CloseHandle(created_event);
-    result = WaitForSingleObject(existing_event, INFINITE);
-    assert(result == WAIT_OBJECT_0);
-  }
+  return TRUE;
 }
 
-
-void uv_once(uv_once_t* guard, void (*callback)(void)) {
-  /* Fast case - avoid WaitForSingleObject. */
-  if (guard->ran) {
-    return;
-  }
-
-  uv__once_inner(guard, callback);
+void uv_once(uv_once_t* guard, uv__once_cb callback) {
+  uv__once_data_t data = { .callback = callback };
+  InitOnceExecuteOnce(&guard->init_once, uv__once_inner, (void*) &data, NULL);
 }