ChangeLogTag:Mon Aug 4 03:26:30 UTC 2003 Don Hinton <dhinton@dresystems.com>

1 files changed, 100 insertions, 0 deletions

diff --git a/ace/Null_Semaphore.h b/ace/Null_Semaphore.h
new file mode 100644
index 00000000000..fbd045f5455
--- /dev/null
+++ b/ace/Null_Semaphore.h
@@ -0,0 +1,100 @@
+// -*- C++ -*-
+
+//==========================================================================
+/**
+ *  @file    Null_Semaphore.h
+ *
+ *  $Id$
+ *
+ *   Moved from Synch.h.
+ *
+ *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
+ */
+//==========================================================================
+
+#ifndef ACE_NULL_SEMAPHORE_H
+#define ACE_NULL_SEMAPHORE_H
+#include /**/ "ace/pre.h"
+
+#include "ace/ACE_export.h"
+
+#if !defined (ACE_LACKS_PRAGMA_ONCE)
+# pragma once
+#endif /* ACE_LACKS_PRAGMA_ONCE */
+
+#include "ace/os_include/os_errno.h"
+
+class ACE_Time_Value;
+
+/**
+ * @class ACE_Null_Semaphore
+ *
+ * @brief Implement a do nothing <ACE_Semaphore>, i.e., all the methods are
+ * no ops.
+ *
+ * Although the methods are no-ops, the return values are different for
+ * the blocking as opposed to timed acquires.  The blocking version of
+ * acquire() is often used to serialize access to a critical section,
+ * whereas the timed version is often used to wait for another thread
+ * to update some condition or change some shared state.  When using an
+ * ACE_Null_Semaphore, however, there's no other thread involved to
+ * change a state or condition (otherwise, a null semaphore would be
+ * inappropriate).  Returning an error value signifies that the
+ * state or condition has not been (and can't be) changed, which is
+ * consistent with the behavior of the threaded case where a timeout
+ * occurs before the state or condition is changed.
+ */
+class ACE_Export ACE_Null_Semaphore
+{
+public:
+  ACE_Null_Semaphore (unsigned int count = 1, // By default make this unlocked.
+                       int type = 0,
+                       const ACE_TCHAR *name = 0,
+                       void * = 0,
+                       int max = 0x7fffffff) {}
+  ~ACE_Null_Semaphore (void) {}
+  /// Return 0.
+  int remove (void) {return 0;}
+
+  /// Return 0.
+  int acquire (void) {return 0;}
+
+  /// Return -1 with <errno> == <ETIME>.
+  int acquire (ACE_Time_Value &) {errno = ETIME; return -1;}
+
+  /// Return -1 with <errno> == <ETIME>.
+  int acquire (ACE_Time_Value *) {errno = ETIME; return -1;}
+
+  /// Return 0.
+  int tryacquire (void) {return 0;}
+
+  /// Return 0.
+  int release (void) {return 0;}
+
+  /// Return 0.
+  int release (size_t) {return 0;}
+
+  /// Return 0.
+  int acquire_write (void) {return 0;}
+
+  /// Return 0.
+  int tryacquire_write (void) {return 0;}
+
+  /// Return 0.
+  int tryacquire_write_upgrade (void) {return 0;}
+
+  /// Return 0.
+  int acquire_read (void) {return 0;}
+
+  /// Return 0.
+  int tryacquire_read (void) {return 0;}
+
+  /// Dump the state of an object.
+  void dump (void) const {}
+
+  /// Declare the dynamic allocation hooks.
+  //ACE_ALLOC_HOOK_DECLARE;
+};
+
+#include /**/ "ace/post.h"
+#endif /* ACE_NULL_SEMAPHORE_H */