X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=platform%2Fwin32%2Ffunctions%2Fthreads%2Fcall_once.c;fp=platform%2Fwin32%2Ffunctions%2Fthreads%2Fcall_once.c;h=675e00029ecc436f0b4550c3e9ede014c95ab219;hb=639bad513ab9399ed9a8c588a476a10dbe6c9478;hp=0000000000000000000000000000000000000000;hpb=008908f7a61acf9df1248c005378a3c4b4393547;p=pdclib

diff --git a/platform/win32/functions/threads/call_once.c b/platform/win32/functions/threads/call_once.c
new file mode 100644
index 0000000..675e000
--- /dev/null
+++ b/platform/win32/functions/threads/call_once.c
@@ -0,0 +1,79 @@
+#ifndef REGTEST
+#include <threads.h>
+#include <windows.h>
+
+static volatile HANDLE onceHandle = NULL;
+
+static void initOnceHandle( _PDCLIB_once_flag *flag )
+{
+    HANDLE tOnceHandle = CreateEvent(NULL, TRUE, TRUE, NULL);
+    HANDLE oldVal 
+        = InterlockedCompareExchangePointer(&flag->_Handle, tOnceHandle, NULL);
+    if(oldVal != NULL)
+        CloseHandle(tOnceHandle);
+}
+
+void _PDCLIB_call_once(_PDCLIB_once_flag *flag, void (*func)(void))
+{
+   if(!flag->_Handle) initOnceHandle(flag);
+
+   long oldVal = InterlockedCompareExchange(&flag->_State, 1, -1);
+   for(;;) {
+        if(oldVal == 0) {
+            // Initialized
+            return;
+        } else if(oldVal == -1) {
+            // We are doing the initialization
+            func();
+            if(InterlockedDecrement(&flag->_State) == 0)
+                CloseHandle(flag->_Handle);
+            SetEvent(flag->_Handle);
+            return;
+        } else {
+            // Somebody else is initializing - we are waiting
+            long newOldVal = InterlockedCompareExchange(&flag->_State, oldVal, 
+                                                        oldVal+1);
+            if(newOldVal == oldVal) {
+                // We incremented the "waiters" counter
+                if(WaitForSingleObject(flag->_Handle, INFINITE) != WAIT_OBJECT_0)
+                    abort();
+                if(InterlockedDecrement(&flag->_State) == 0)
+                    CloseHandle(flag->_Handle);
+                return;
+            } else {
+                oldVal = newOldVal;
+                continue;
+            }
+        }
+    }
+}
+#endif
+
+#ifdef TEST
+#include <_PDCLIB_test.h>
+
+#ifndef REGTEST
+static int count = 0;
+static once_flag once = ONCE_FLAG_INIT;
+
+static void do_once(void)
+{
+    count++;
+}
+#endif
+
+int main( void )
+{
+#ifndef REGTEST
+    TESTCASE(count == 0);
+    call_once(&once, do_once);
+    TESTCASE(count == 1);
+    call_once(&once, do_once);
+    TESTCASE(count == 1);
+    do_once();
+    TESTCASE(count == 2);
+#endif
+    return TEST_RESULTS;
+}
+
+#endif