Include <config.h>.

[gnulib.git] / lib / lock.c

diff --git a/lib/lock.c b/lib/lock.c
index cbf9f11..a860459 100644 (file)
--- a/lib/lock.c
+++ b/lib/lock.c
@@ -32,6 +32,43 @@
 
 /* Use the POSIX threads library.  */
 
+# if PTHREAD_IN_USE_DETECTION_HARD
+
+/* The function to be executed by a dummy thread.  */
+static void *
+dummy_thread_func (void *arg)
+{
+  return arg;
+}
+
+int
+glthread_in_use (void)
+{
+  static int tested;
+  static int result; /* 1: linked with -lpthread, 0: only with libc */
+
+  if (!tested)
+    {
+      pthread_t thread;
+
+      if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
+       /* Thread creation failed.  */
+       result = 0;
+      else
+       {
+         /* Thread creation works.  */
+         void *retval;
+         if (pthread_join (thread, &retval) != 0)
+           abort ();
+         result = 1;
+       }
+      tested = 1;
+    }
+  return result;
+}
+
+# endif
+
 /* -------------------------- gl_lock_t datatype -------------------------- */
 
 /* ------------------------- gl_rwlock_t datatype ------------------------- */
@@ -322,6 +359,26 @@ glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
 
 # endif
 
+/* -------------------------- gl_once_t datatype -------------------------- */
+
+static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;
+
+int
+glthread_once_singlethreaded (pthread_once_t *once_control)
+{
+  /* We don't know whether pthread_once_t is an integer type, a floating-point
+     type, a pointer type, or a structure type.  */
+  char *firstbyte = (char *)once_control;
+  if (*firstbyte == *(const char *)&fresh_once)
+    {
+      /* First time use of once_control.  Invert the first byte.  */
+      *firstbyte = ~ *(const char *)&fresh_once;
+      return 1;
+    }
+  else
+    return 0;
+}
+
 #endif
 
 /* ========================================================================= */
@@ -336,6 +393,30 @@ glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
 
 /* --------------------- gl_recursive_lock_t datatype --------------------- */
 
+/* -------------------------- gl_once_t datatype -------------------------- */
+
+void
+glthread_once_call (void *arg)
+{
+  void (**gl_once_temp_addr) (void) = (void (**) (void)) arg;
+  void (*initfunction) (void) = *gl_once_temp_addr;
+  initfunction ();
+}
+
+int
+glthread_once_singlethreaded (pth_once_t *once_control)
+{
+  /* We know that pth_once_t is an integer type.  */
+  if (*once_control == PTH_ONCE_INIT)
+    {
+      /* First time use of once_control.  Invert the marker.  */
+      *once_control = ~ PTH_ONCE_INIT;
+      return 1;
+    }
+  else
+    return 0;
+}
+
 #endif
 
 /* ========================================================================= */
@@ -397,6 +478,41 @@ glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
     abort ();
 }
 
+/* -------------------------- gl_once_t datatype -------------------------- */
+
+void
+glthread_once (gl_once_t *once_control, void (*initfunction) (void))
+{
+  if (!once_control->inited)
+    {
+      /* Use the mutex to guarantee that if another thread is already calling
+        the initfunction, this thread waits until it's finished.  */
+      if (mutex_lock (&once_control->mutex) != 0)
+       abort ();
+      if (!once_control->inited)
+       {
+         once_control->inited = 1;
+         initfunction ();
+       }
+      if (mutex_unlock (&once_control->mutex) != 0)
+       abort ();
+    }
+}
+
+int
+glthread_once_singlethreaded (gl_once_t *once_control)
+{
+  /* We know that gl_once_t contains an integer type.  */
+  if (!once_control->inited)
+    {
+      /* First time use of once_control.  Invert the marker.  */
+      once_control->inited = ~ 0;
+      return 1;
+    }
+  else
+    return 0;
+}
+
 #endif
 
 /* ========================================================================= */
@@ -764,6 +880,45 @@ glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
   lock->guard.done = 0;
 }
 
+/* -------------------------- gl_once_t datatype -------------------------- */
+
+void
+glthread_once (gl_once_t *once_control, void (*initfunction) (void))
+{
+  if (once_control->inited <= 0)
+    {
+      if (InterlockedIncrement (&once_control->started) == 0)
+       {
+         /* This thread is the first one to come to this once_control.  */
+         InitializeCriticalSection (&once_control->lock);
+         EnterCriticalSection (&once_control->lock);
+         once_control->inited = 0;
+         initfunction ();
+         once_control->inited = 1;
+         LeaveCriticalSection (&once_control->lock);
+       }
+      else
+       {
+         /* Undo last operation.  */
+         InterlockedDecrement (&once_control->started);
+         /* Some other thread has already started the initialization.
+            Yield the CPU while waiting for the other thread to finish
+            initializing and taking the lock.  */
+         while (once_control->inited < 0)
+           Sleep (0);
+         if (once_control->inited <= 0)
+           {
+             /* Take the lock.  This blocks until the other thread has
+                finished calling the initfunction.  */
+             EnterCriticalSection (&once_control->lock);
+             LeaveCriticalSection (&once_control->lock);
+             if (!(once_control->inited > 0))
+               abort ();
+           }
+       }
+    }
+}
+
 #endif
 
 /* ========================================================================= */