ACE/ace/SV_Semaphore_Simple.h

   1 // -*- C++ -*-
   2
   3 //==========================================================================
   4 /**
   5  *  @file    SV_Semaphore_Simple.h
   6  *
   7  *  @author Douglas C. Schmidt <d.schmidt@vanderbilt.edu>
   8  */
   9 //==========================================================================
  10
  11 #ifndef ACE_SV_SEMAPHORE_SIMPLE_H
  12 #define ACE_SV_SEMAPHORE_SIMPLE_H
  13
  14 #include /**/ "ace/pre.h"
  15
  16 #include /**/ "ace/ACE_export.h"
  17
  18 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  19 # pragma once
  20 #endif /* ACE_LACKS_PRAGMA_ONCE */
  21
  22 #include "ace/os_include/sys/os_stat.h"
  23 #include "ace/os_include/sys/os_ipc.h"
  24 #include "ace/os_include/sys/os_sem.h"
  25 #include "ace/Default_Constants.h"
  26
  27 #if defined (ACE_WIN32)
  28    // Default semaphore key and mutex name
  29 #  if !defined (ACE_DEFAULT_SEM_KEY)
  30 #    define ACE_DEFAULT_SEM_KEY const_cast <char*>("ACE_SEM_KEY")
  31 #  endif /* ACE_DEFAULT_SEM_KEY */
  32 #else /* !defined (ACE_WIN32) */
  33    // Default semaphore key
  34 #  if !defined (ACE_DEFAULT_SEM_KEY)
  35 #    define ACE_DEFAULT_SEM_KEY 1234
  36 #  endif /* ACE_DEFAULT_SEM_KEY */
  37 #endif /* ACE_WIN32 */
  38
  39 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  40
  41 /**
  42  * @class ACE_SV_Semaphore_Simple
  43  *
  44  * @brief This is a simple semaphore package that assumes there are
  45  * no race conditions for initialization (i.e., the order of
  46  * process startup must be well defined).
  47  */
  48 class ACE_Export ACE_SV_Semaphore_Simple
  49 {
  50 public:
  51   enum
  52   {
  53     ACE_CREATE = IPC_CREAT,
  54     ACE_EXCL = IPC_EXCL,
  55     ACE_OPEN = 0
  56   };
  57
  58   ACE_SV_Semaphore_Simple ();
  59   ACE_SV_Semaphore_Simple (key_t key,
  60                            short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  61                            int initial_value = 1,
  62                            u_short nsems = 1,
  63                            mode_t perms = ACE_DEFAULT_FILE_PERMS);
  64   ACE_SV_Semaphore_Simple (const char *name,
  65                            short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  66                            int initial_value = 1,
  67                            u_short nsems = 1,
  68                            mode_t perms = ACE_DEFAULT_FILE_PERMS);
  69 #if defined (ACE_HAS_WCHAR)
  70   ACE_SV_Semaphore_Simple (const wchar_t *name,
  71                            short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  72                            int initial_value = 1,
  73                            u_short nsems = 1,
  74                            mode_t perms = ACE_DEFAULT_FILE_PERMS);
  75 #endif /* ACE_HAS_WCHAR */
  76
  77   ~ACE_SV_Semaphore_Simple ();
  78
  79   int open (const char *name,
  80             short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  81             int initial_value = 1,
  82             u_short nsems = 1,
  83             mode_t perms = ACE_DEFAULT_FILE_PERMS);
  84
  85 #if defined (ACE_HAS_WCHAR)
  86   int open (const wchar_t *name,
  87             short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  88             int initial_value = 1,
  89             u_short nsems = 1,
  90             mode_t perms = ACE_DEFAULT_FILE_PERMS);
  91 #endif /* ACE_HAS_WCHAR */
  92
  93   /// Open or create one or more SV_Semaphores.  We return 0 if all is
  94   /// OK, else -1.
  95   int open (key_t key,
  96             short flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
  97             int initial_value = 1,
  98             u_short nsems = 1,
  99             mode_t perms = ACE_DEFAULT_FILE_PERMS);
 100
 101   /// Close a ACE_SV_Semaphore, marking it as invalid for subsequent
 102   /// operations...
 103   int close ();
 104
 105   /**
 106    * Remove all SV_Semaphores associated with a particular key.  This
 107    * call is intended to be called from a server, for example, when it
 108    * is being shut down, as we do an IPC_RMID on the ACE_SV_Semaphore,
 109    * regardless of whether other processes may be using it or not.
 110    * Most other processes should use close() below.
 111    */
 112   int remove () const;
 113
 114   // = Semaphore acquire and release methods.
 115   /**
 116    * Wait until a ACE_SV_Semaphore's value is greater than 0, the
 117    * decrement it by 1 and return. Dijkstra's P operation, Tannenbaums
 118    * DOWN operation.
 119    */
 120   int acquire (u_short n = 0, short flags = 0) const;
 121
 122   /// Acquire a semaphore for reading.
 123   int acquire_read (u_short n = 0, short flags = 0) const;
 124
 125   /// Acquire a semaphore for writing
 126   int acquire_write (u_short n = 0, short flags = 0) const;
 127
 128   /// Non-blocking version of <acquire>.
 129   int tryacquire (u_short n = 0, short flags = 0) const;
 130
 131   /// Try to acquire the semaphore for reading.
 132   int tryacquire_read (u_short n = 0, short flags = 0) const;
 133
 134   /// Try to acquire the semaphore for writing.
 135   int tryacquire_write (u_short n = 0, short flags = 0) const;
 136
 137   /// Increment ACE_SV_Semaphore by one. Dijkstra's V operation,
 138   /// Tannenbaums UP operation.
 139   int release (u_short n = 0, short flags = 0) const;
 140
 141   // = Semaphore operation methods.
 142   /// General ACE_SV_Semaphore operation. Increment or decrement by a
 143   /// specific amount (positive or negative; amount can`t be zero).
 144   int op (short val, u_short semnum = 0, short flags = SEM_UNDO) const;
 145
 146   /// General ACE_SV_Semaphore operation on an array of SV_Semaphores.
 147   int op (sembuf op_vec[], u_short nsems) const;
 148
 149   // = Semaphore control methods.
 150   int control (int cmd, semun arg, u_short n = 0) const;
 151   int control (int cmd, int value = 0, u_short n = 0) const;
 152
 153   /// Get underlying internal id.
 154   int get_id () const;
 155
 156   /// Dump the state of an object.
 157   void dump () const;
 158
 159   /// Declare the dynamic allocation hooks.
 160   ACE_ALLOC_HOOK_DECLARE;
 161
 162 protected:
 163   /// Semaphore key.
 164   key_t key_;
 165
 166   /// Internal ID to identify the semaphore group within this process.
 167   int internal_id_;
 168
 169   /// Number of semaphores we're creating.
 170   int sem_number_;
 171
 172 #ifdef ACE_HAS_SYSV_IPC
 173   /**
 174    * Convert name to key This function is used internally to create
 175    * keys for the semaphores. A valid name contains letters and
 176    * digits only and MUST start with a letter.
 177    *
 178    * The method for generating names is not very sophisticated, so
 179    * caller should not pass strings which match each other for the first
 180    * LUSED characters when he wants to get a different key.
 181    */
 182   int init (key_t k = static_cast<key_t> (ACE_INVALID_SEM_KEY),
 183             int i = -1);
 184 #endif
 185
 186   key_t name_2_key (const char *name);
 187 };
 188
 189 ACE_END_VERSIONED_NAMESPACE_DECL
 190
 191 #if defined (__ACE_INLINE__)
 192 #include "ace/SV_Semaphore_Simple.inl"
 193 #endif /* __ACE_INLINE__ */
 194
 195 #include /**/ "ace/post.h"
 196
 197 #endif /* _SV_SEMAPHORE_SIMPLE_H */