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Process_Semaphore.h

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00001 /* -*- C++ -*- */
00002 
00003 //=============================================================================
00004 /**
00005  *  @file    Process_Semaphore.h
00006  *
00007  *  $Id: Process_Semaphore.h,v 1.1.1.1 2001/12/04 14:33:07 chad Exp $
00008  *
00009  *   Wrapper for Dijkstra style general semaphores that work
00010  *   across processes.
00011  *
00012  *
00013  *  @author Doug Schmidt
00014  */
00015 //=============================================================================
00016 
00017 
00018 #ifndef ACE_PROCESS_SEMAPHORE_H
00019 #define ACE_PROCESS_SEMAPHORE_H
00020 #include "ace/pre.h"
00021 
00022 #include "ace/Synch.h"
00023 
00024 #if !defined (ACE_LACKS_PRAGMA_ONCE)
00025 # pragma once
00026 #endif /* ACE_LACKS_PRAGMA_ONCE */
00027 
00028 #if !(defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS))
00029 #include "ace/SV_Semaphore_Complex.h"
00030 #endif /* !(ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS) */
00031 
00032 /**
00033  * @class ACE_Process_Semaphore
00034  *
00035  * @brief Wrapper for Dijkstra style general semaphores that work
00036  * across processes.
00037  */
00038 class ACE_Export ACE_Process_Semaphore
00039 {
00040 public:
00041   /// Initialize the semaphore, with an initial value of <count> and a
00042   /// maximum value of <max>.
00043   ACE_Process_Semaphore (u_int count = 1, // By default make this unlocked.
00044                          const ACE_TCHAR *name = 0,
00045                          void * = 0,
00046                          int max = 0x7FFFFFFF);
00047 
00048   /**
00049    * This method is a no-op, i.e., it doesn't remove the semaphore.
00050    * If you want to remove the semaphore, you must call the <remove>
00051    * method explicitly.
00052    */
00053   ~ACE_Process_Semaphore (void);
00054 
00055   /**
00056    * Explicitly destroy the semaphore.  Note that only one thread
00057    * should call this method since it doesn't protect against race
00058    * conditions.
00059    */
00060   int remove (void);
00061 
00062   /// Block the thread until the semaphore count becomes greater than
00063   /// 0, then decrement it.
00064   int acquire (void);
00065 
00066   /**
00067    * Conditionally decrement the semaphore if count is greater than 0
00068    * (i.e., won't block).  Returns -1 on failure.  If we "failed"
00069    * because someone else already had the lock, <errno> is set to
00070    * <EBUSY>.
00071    */
00072   int tryacquire (void);
00073 
00074   /// Increment the semaphore, potentially unblocking a waiting thread.
00075   int release (void);
00076 
00077   /**
00078    * Acquire semaphore ownership.  This calls <acquire> and is only
00079    * here to make the <ACE_Process_Semaphore> interface consistent
00080    * with the other synchronization APIs.
00081    */
00082   int acquire_read (void);
00083 
00084   /**
00085    * Acquire semaphore ownership.  This calls <acquire> and is only
00086    * here to make the <ACE_Process_Semaphore> interface consistent
00087    * with the other synchronization APIs.
00088    */
00089   int acquire_write (void);
00090 
00091   /**
00092    * Conditionally acquire semaphore (i.e., won't block).  This calls
00093    * <tryacquire> and is only here to make the <ACE_Process_Semaphore>
00094    * interface consistent with the other synchronization APIs.
00095    * Returns -1 on failure.  If we "failed" because someone else
00096    * already had the lock, <errno> is set to <EBUSY>.
00097    */
00098   int tryacquire_read (void);
00099 
00100   /**
00101    * Conditionally acquire semaphore (i.e., won't block).  This calls
00102    * <tryacquire> and is only here to make the <ACE_Process_Semaphore>
00103    * interface consistent with the other synchronization APIs.
00104    * Returns -1 on failure.  If we "failed" because someone else
00105    * already had the lock, <errno> is set to <EBUSY>.
00106    */
00107   int tryacquire_write (void);
00108 
00109   /**
00110    * This is only here to make the <ACE_Process_Semaphore>
00111    * interface consistent with the other synchronization APIs.
00112    * Assumes the caller has already acquired the semaphore using one of
00113    * the above calls, and returns 0 (success) always.
00114    */
00115   int tryacquire_write_upgrade (void);
00116 
00117 #if defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS)
00118   /// Return the underlying lock.
00119   const ACE_sema_t &lock (void) const;
00120 #endif /* ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS */
00121 
00122   /// Dump the state of an object.
00123   void dump (void) const;
00124 
00125   /// Declare the dynamic allocation hooks.
00126   ACE_ALLOC_HOOK_DECLARE;
00127 
00128 protected:
00129 #if defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS)
00130   ACE_Semaphore lock_;
00131 #else
00132   /// We need this to get the right semantics...
00133   ACE_SV_Semaphore_Complex lock_;
00134 #endif /* ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS */
00135 };
00136 
00137 #if defined (__ACE_INLINE__)
00138 #include "ace/Process_Semaphore.inl"
00139 #endif /* __ACE_INLINE__ */
00140 
00141 #include "ace/post.h"
00142 #endif /* ACE_PROCESS_SEMAPHORE_H */

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