framework/inc/threadhelp/gate.hxx

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  19
  20 #ifndef INCLUDED_FRAMEWORK_INC_THREADHELP_GATE_HXX
  21 #define INCLUDED_FRAMEWORK_INC_THREADHELP_GATE_HXX
  22
  23 #include <boost/noncopyable.hpp>
  24 #include <osl/time.h>
  25 #include <osl/mutex.hxx>
  26 #include <osl/conditn.hxx>
  27
  28 namespace framework{
  29
  30 /*-************************************************************************************************************
  31     @short          implement a gate to block multiple threads at same time or unblock all
  32     @descr          A gate can be used as a negative-condition! You can open a "door" - wait() will not block ...
  33                     or you can close it - wait() blocks till open() is called again.
  34                     Then all currently waiting threads are running immediately - but new ones are blocked!
  35
  36     @attention      To prevent us against wrong using, the default ctor, copy ctor and the =operator are marked private!
  37
  38     @devstatus      ready to use
  39 *//*-*************************************************************************************************************/
  40 class Gate : private boost::noncopyable
  41 {
  42
  43     //  public methods
  44
  45     public:
  46
  47         /*-****************************************************************************************************
  48             @short      ctor
  49             @descr      These initialize the object right as an open gate.
  50         *//*-*****************************************************************************************************/
  51         inline Gate()
  52             :   m_bClosed   ( false )
  53         {
  54             open();
  55         }
  56
  57         /*-****************************************************************************************************
  58             @short      dtor
  59             @descr      Is user forget it - we open the gate ...
  60                         blocked threads can running ... but I don't know
  61                         if it's right - we are destroyed yet!?
  62         *//*-*****************************************************************************************************/
  63         inline ~Gate()
  64         {
  65             open();
  66         }
  67
  68         /*-****************************************************************************************************
  69             @short      open the gate
  70             @descr      A wait() call will not block then.
  71
  72             @seealso    method close()
  73         *//*-*****************************************************************************************************/
  74         void open()
  75         {
  76             // We must safe access to our internal member!
  77             ::osl::MutexGuard aLock( m_aAccessLock );
  78             // Set condition -> wait don't block any longer -> gate is open
  79             m_aPassage.set();
  80             // Check if operation was successful!
  81             // Check returns false if condition isn't set => m_bClosed will be true then => we must return false; opening failed
  82             m_bClosed = !m_aPassage.check();
  83         }
  84
  85         /*-****************************************************************************************************
  86             @short      close the gate
  87             @descr      A wait() call will block then.
  88
  89             @seealso    method open()
  90         *//*-*****************************************************************************************************/
  91         void close()
  92         {
  93             // We must safe access to our internal member!
  94             ::osl::MutexGuard aLock( m_aAccessLock );
  95             // Reset condition -> wait blocks now -> gate is closed
  96             m_aPassage.reset();
  97             // Check if operation was successful!
  98             // Check returns false if condition was reseted => m_bClosed will be true then => we can return true; closing ok
  99             m_bClosed = !m_aPassage.check();
 100         }
 101
 102         /*-****************************************************************************************************
 103             @short      must be called to pass the gate
 104             @descr      If gate "open"   => wait() will not block.
 105                         If gate "closed" => wait() will block till somewhere open it again.
 106
 107             @seealso    method wait()
 108             @seealso    method open()
 109
 110             @param      "pTimeOut", optional parameter to wait a certain time
 111             @return     true, if wait was successful (gate was opened)
 112                         false, if condition has an error or timeout was reached!
 113
 114             @onerror    We return false.
 115         *//*-*****************************************************************************************************/
 116         bool wait(const TimeValue* pTimeOut = nullptr)
 117         {
 118             // We must safe access to our internal member!
 119             ::osl::ClearableMutexGuard aLock( m_aAccessLock );
 120             // If gate not closed - caller can pass it.
 121             bool bSuccessful = true;
 122             if( m_bClosed )
 123             {
 124                 // Then we must release used access lock -
 125                 // because next call will block ...
 126                 // and if we hold the access lock nobody else can use this object without a dadlock!
 127                 aLock.clear();
 128                 // Wait for opening gate ...
 129                 bSuccessful = ( m_aPassage.wait( pTimeOut ) == ::osl::Condition::result_ok );
 130             }
 131
 132             return bSuccessful;
 133         }
 134
 135     //  private member
 136
 137     private:
 138
 139         ::osl::Mutex        m_aAccessLock;
 140         ::osl::Condition    m_aPassage;
 141         bool                m_bClosed;
 142
 143 };      //  class Gate
 144
 145 }       //  namespace framework
 146
 147 #endif // INCLUDED_FRAMEWORK_INC_THREADHELP_GATE_HXX
 148
 149 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */