summaryrefslogtreecommitdiff
path: root/ace/SV_Semaphore_Simple.h
blob: ac6126b2e8ce9868e49d69bffa92b2189f02b327 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
/* -*- C++ -*- */

//=============================================================================
/**
 *  @file    SV_Semaphore_Simple.h
 *
 *  $Id$
 *
 *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
 */
//=============================================================================

#ifndef ACE_SV_SEMAPHORE_SIMPLE_H
#define ACE_SV_SEMAPHORE_SIMPLE_H
#include "ace/pre.h"

#include "ace/ACE.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

/**
 * @class ACE_SV_Semaphore_Simple
 *
 * @brief This is a simple semaphore package that assumes there are
 * no race conditions for initialization (i.e., the order of
 * process startup must be well defined).
 */
class ACE_Export ACE_SV_Semaphore_Simple
{
public:
  enum
  {
    ACE_CREATE = IPC_CREAT,
    ACE_EXCL = IPC_EXCL,
    ACE_OPEN = 0
  };

  // = Initialization and termination methods.
  ACE_SV_Semaphore_Simple (void);
  ACE_SV_Semaphore_Simple (key_t key,
                           int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
                           int initial_value = 1,
                           u_short nsems = 1,
                           int perms = ACE_DEFAULT_FILE_PERMS);
  ACE_SV_Semaphore_Simple (const char *name,
                           int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
                           int initial_value = 1,
                           u_short nsems = 1,
                           int perms = ACE_DEFAULT_FILE_PERMS);
  ~ACE_SV_Semaphore_Simple (void);

  int open (const char *name,
            int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
            int initial_value = 1,
            u_short nsems = 1,
            int perms = ACE_DEFAULT_FILE_PERMS);

  /// Open or create one or more SV_Semaphores.  We return 0 if all is
  /// OK, else -1.
  int open (key_t key,
            int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
            int initial_value = 1,
            u_short nsems = 1,
            int perms = ACE_DEFAULT_FILE_PERMS);

  /// Close a ACE_SV_Semaphore, marking it as invalid for subsequent
  /// operations...
  int close (void);

  /**
   * Remove all SV_Semaphores associated with a particular key.  This
   * call is intended to be called from a server, for example, when it
   * is being shut down, as we do an IPC_RMID on the ACE_SV_Semaphore,
   * regardless of whether other processes may be using it or not.
   * Most other processes should use <close> below.
   */
  int remove (void) const;

  // = Semaphore acquire and release methods.
  /**
   * Wait until a ACE_SV_Semaphore's value is greater than 0, the
   * decrement it by 1 and return. Dijkstra's P operation, Tannenbaums
   * DOWN operation.
   */
  int acquire (u_short n = 0, int flags = 0) const;

  /// Acquire a semaphore for reading.
  int acquire_read (u_short n = 0, int flags = 0) const;

  /// Acquire a semaphore for writing
  int acquire_write (u_short n = 0, int flags = 0) const;

  /// Non-blocking version of <acquire>.
  int tryacquire (u_short n = 0, int flags = 0) const;

  /// Try to acquire the semaphore for reading.
  int tryacquire_read (u_short n = 0, int flags = 0) const;

  /// Try to acquire the semaphore for writing.
  int tryacquire_write (u_short n = 0, int flags = 0) const;

  /// Increment ACE_SV_Semaphore by one. Dijkstra's V operation,
  /// Tannenbaums UP operation.
  int release (u_short n = 0, int flags = 0) const;

  // = Semaphore operation methods.
  /// General ACE_SV_Semaphore operation. Increment or decrement by a
  /// specific amount (positive or negative; amount can`t be zero).
  int op (int val, u_short semnum = 0, int flags = SEM_UNDO) const;

  /// General ACE_SV_Semaphore operation on an array of SV_Semaphores.
  int op (sembuf op_vec[], u_short nsems) const;

  // = Semaphore control methods.
  int control (int cmd, semun arg, u_short n = 0) const;
  int control (int cmd, int value = 0, u_short n = 0) const;

  /// Get underlying internal id.
  int get_id (void) const;

  /// Dump the state of an object.
  void dump (void) const;

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

protected:
  /// Semaphore key.
  key_t key_;

  /// Internal ID to identify the semaphore group within this process.
  int internal_id_;

  /// Number of semaphores we're creating.
  int sem_number_;

  /**
   * Convert name to key This function is used internally to create
   * keys for the semaphores. A valid name contains letters and
   * digits only and MUST start with a letter.
   *
   * The method for generating names is not very sophisticated, so
   * caller should not pass strings which match each other for the first
   * LUSED characters when he wants to get a different key.
   */
  int init (key_t k = ACE_static_cast (key_t, ACE_INVALID_SEM_KEY),
            int i = -1);
  key_t name_2_key (const char *name);
};

#if !defined (ACE_LACKS_INLINE_FUNCTIONS)
#include "ace/SV_Semaphore_Simple.i"
#endif

#include "ace/post.h"
#endif /* _SV_SEMAPHORE_SIMPLE_H */