pd.if.org Git - pdclib/blob - platform/win32/functions/threads/call_once.c

   1 #ifndef REGTEST\r
   2 #include <threads.h>\r
   3 #include <windows.h>\r
   4 \r
   5 static volatile HANDLE onceHandle = NULL;\r
   6 \r
   7 static void initOnceHandle( _PDCLIB_once_flag *flag )\r
   8 {\r
   9     HANDLE tOnceHandle = CreateEvent(NULL, TRUE, TRUE, NULL);\r
  10     HANDLE oldVal \r
  11         = InterlockedCompareExchangePointer(&flag->_Handle, tOnceHandle, NULL);\r
  12     if(oldVal != NULL)\r
  13         CloseHandle(tOnceHandle);\r
  14 }\r
  15 \r
  16 void _PDCLIB_call_once(_PDCLIB_once_flag *flag, void (*func)(void))\r
  17 {\r
  18    if(!flag->_Handle) initOnceHandle(flag);\r
  19 \r
  20    long oldVal = InterlockedCompareExchange(&flag->_State, 1, -1);\r
  21    for(;;) {\r
  22         if(oldVal == 0) {\r
  23             // Initialized\r
  24             return;\r
  25         } else if(oldVal == -1) {\r
  26             // We are doing the initialization\r
  27             func();\r
  28             if(InterlockedDecrement(&flag->_State) == 0)\r
  29                 CloseHandle(flag->_Handle);\r
  30             SetEvent(flag->_Handle);\r
  31             return;\r
  32         } else {\r
  33             // Somebody else is initializing - we are waiting\r
  34             long newOldVal = InterlockedCompareExchange(&flag->_State, oldVal, \r
  35                                                         oldVal+1);\r
  36             if(newOldVal == oldVal) {\r
  37                 // We incremented the "waiters" counter\r
  38                 if(WaitForSingleObject(flag->_Handle, INFINITE) != WAIT_OBJECT_0)\r
  39                     abort();\r
  40                 if(InterlockedDecrement(&flag->_State) == 0)\r
  41                     CloseHandle(flag->_Handle);\r
  42                 return;\r
  43             } else {\r
  44                 oldVal = newOldVal;\r
  45                 continue;\r
  46             }\r
  47         }\r
  48     }\r
  49 }\r
  50 #endif\r
  51 \r
  52 #ifdef TEST\r
  53 #include <_PDCLIB_test.h>\r
  54 \r
  55 #ifndef REGTEST\r
  56 static int count = 0;\r
  57 static once_flag once = ONCE_FLAG_INIT;\r
  58 \r
  59 static void do_once(void)\r
  60 {\r
  61     count++;\r
  62 }\r
  63 #endif\r
  64 \r
  65 int main( void )\r
  66 {\r
  67 #ifndef REGTEST\r
  68     TESTCASE(count == 0);\r
  69     call_once(&once, do_once);\r
  70     TESTCASE(count == 1);\r
  71     call_once(&once, do_once);\r
  72     TESTCASE(count == 1);\r
  73     do_once();\r
  74     TESTCASE(count == 2);\r
  75 #endif\r
  76     return TEST_RESULTS;\r
  77 }\r
  78 \r
  79 #endif\r