libbase/SharedMem.h

   1 //
   2 //   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
   3 //   Foundation, Inc
   4 //
   5 // This program is free software; you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation; either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // This program is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with this program; if not, write to the Free Software
  17 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18
  19 #ifndef GNASH_SHM_H
  20 #define GNASH_SHM_H
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include "gnashconfig.h"
  24 #endif
  25
  26 #include <boost/cstdint.hpp>
  27
  28 #if defined (WIN32)
  29 // Include for HANDLE
  30 #include <windows.h>
  31 #else
  32 // key_t
  33 #include <sys/types.h>
  34 #endif
  35
  36 #include "dsodefs.h" //For DSOEXPORT
  37
  38 // Forward declarations
  39 namespace gnash {
  40         class fn_call;
  41 }
  42
  43 namespace gnash {
  44
  45 class SharedMem
  46 {
  47 public:
  48
  49     typedef boost::uint8_t* iterator;
  50
  51     /// The beginning of the SharedMem section.
  52     //
  53     /// This is only valid after attach() has returned true. You can check
  54     /// with the function attached().
  55     iterator begin() const {
  56         return _addr;
  57     }
  58
  59     /// The end of the SharedMem section.
  60     //
  61     /// This is only valid after attach() has returned true.
  62     iterator end() const {
  63         return _addr + _size;
  64     }
  65
  66     /// Construct a SharedMem with the requested size.
  67     //
  68     /// @param size     The size of the shared memory section. If successfully
  69     ///                 created, the segment will be exactly this size and
  70     ///                 is not resizable.
  71     DSOEXPORT SharedMem(size_t size);
  72
  73     /// Destructor.
  74     DSOEXPORT ~SharedMem();
  75
  76     /// Initialize the shared memory segment
  77     //
  78     /// This is called by LocalConnection when either connect() or send()
  79     /// is called.
  80     DSOEXPORT bool attach();
  81
  82     /// Use to get a scoped semaphore lock on the shared memory.
  83     class Lock
  84     {
  85     public:
  86         Lock(const SharedMem& s) : _s(s), _locked(s.lock()) {}
  87         ~Lock() { if (_locked) _s.unlock(); }
  88         bool locked() const {
  89             return _locked;
  90         }
  91     private:
  92         const SharedMem& _s;
  93         bool _locked;
  94     };
  95
  96 private:
  97
  98     /// Get a semaphore lock if possible
  99     //
 100     /// @return     true if successful, false if not.
 101     DSOEXPORT bool lock() const;
 102
 103     /// Release a semaphore lock if possible
 104     //
 105     /// @return     true if successful, false if not.
 106     DSOEXPORT bool unlock() const;
 107
 108     iterator _addr;
 109
 110     const size_t _size;
 111
 112     // Semaphore ID.
 113     int _semid;
 114
 115     // Shared memory ID.
 116     int _shmid;
 117
 118 #if !defined(WIN32)
 119     key_t _shmkey;
 120 #else
 121     long _shmkey;
 122     HANDLE _shmhandle;
 123 #endif
 124 };
 125
 126 /// Check if the SharedMem has been attached.
 127 //
 128 /// This only checks whether the attach operation was successful, not whether
 129 /// the shared memory still exists and is still attached where it was
 130 /// initially. It is always possible for other processes to remove it while
 131 /// Gnash is using it, but there is nothing we can do about this.
 132 inline bool
 133 attached(const SharedMem& mem) {
 134     return (mem.begin());
 135 }
 136
 137 } // end of gnash namespace
 138
 139 #endif
 140
 141 // Local Variables:
 142 // mode: C++
 143 // indent-tabs-mode: t
 144 // End: