src/unix/wakeuppipe.cpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/unix/wakeuppipe.cpp
   3 // Purpose:     Implementation of wxWakeUpPipe class.
   4 // Author:      Vadim Zeitlin
   5 // Created:     2013-06-09 (extracted from src/unix/evtloopunix.cpp)
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2013 Vadim Zeitlin <vadim@wxwidgets.org>
   8 // Licence:     wxWindows licence
   9 ///////////////////////////////////////////////////////////////////////////////
  10
  11 // ============================================================================
  12 // declarations
  13 // ============================================================================
  14
  15 // ----------------------------------------------------------------------------
  16 // headers
  17 // ----------------------------------------------------------------------------
  18
  19 // for compilers that support precompilation, includes "wx.h".
  20 #include "wx/wxprec.h"
  21
  22 #ifdef __BORLANDC__
  23     #pragma hdrstop
  24 #endif
  25
  26 #ifndef WX_PRECOMP
  27 #endif // WX_PRECOMP
  28
  29 #include "wx/unix/private/wakeuppipe.h"
  30
  31 #include <errno.h>
  32
  33 // ----------------------------------------------------------------------------
  34 // constants
  35 // ----------------------------------------------------------------------------
  36
  37 #define TRACE_EVENTS wxT("events")
  38
  39 // ============================================================================
  40 // wxWakeUpPipe implementation
  41 // ============================================================================
  42
  43 // ----------------------------------------------------------------------------
  44 // initialization
  45 // ----------------------------------------------------------------------------
  46
  47 wxWakeUpPipe::wxWakeUpPipe()
  48 {
  49     m_pipeIsEmpty = true;
  50
  51     if ( !m_pipe.Create() )
  52     {
  53         wxLogError(_("Failed to create wake up pipe used by event loop."));
  54         return;
  55     }
  56
  57
  58     if ( !m_pipe.MakeNonBlocking(wxPipe::Read) )
  59     {
  60         wxLogSysError(_("Failed to switch wake up pipe to non-blocking mode"));
  61         return;
  62     }
  63
  64     wxLogTrace(TRACE_EVENTS, wxT("Wake up pipe (%d, %d) created"),
  65                m_pipe[wxPipe::Read], m_pipe[wxPipe::Write]);
  66 }
  67
  68 // ----------------------------------------------------------------------------
  69 // wakeup handling
  70 // ----------------------------------------------------------------------------
  71
  72 void wxWakeUpPipe::WakeUp()
  73 {
  74     wxCriticalSectionLocker lock(m_pipeLock);
  75
  76     // No need to do anything if the pipe already contains something.
  77     if ( !m_pipeIsEmpty )
  78       return;
  79
  80     if ( write(m_pipe[wxPipe::Write], "s", 1) != 1 )
  81     {
  82         // don't use wxLog here, we can be in another thread and this could
  83         // result in dead locks
  84         perror("write(wake up pipe)");
  85     }
  86     else
  87     {
  88         // We just wrote to it, so it's not empty any more.
  89         m_pipeIsEmpty = false;
  90     }
  91 }
  92
  93 void wxWakeUpPipe::OnReadWaiting()
  94 {
  95     // got wakeup from child thread, remove the data that provoked it from the
  96     // pipe
  97
  98     wxCriticalSectionLocker lock(m_pipeLock);
  99
 100     char buf[4];
 101     for ( ;; )
 102     {
 103         const int size = read(GetReadFd(), buf, WXSIZEOF(buf));
 104
 105         if ( size > 0 )
 106         {
 107             wxASSERT_MSG( size == 1, "Too many writes to wake-up pipe?" );
 108
 109             break;
 110         }
 111
 112         if ( size == 0 || (size == -1 && errno == EAGAIN) )
 113         {
 114             // No data available, not an error (but still surprising,
 115             // spurious wakeup?)
 116             break;
 117         }
 118
 119         if ( errno == EINTR )
 120         {
 121             // We were interrupted, try again.
 122             continue;
 123         }
 124
 125         wxLogSysError(_("Failed to read from wake-up pipe"));
 126
 127         return;
 128     }
 129
 130     // The pipe is empty now, so future calls to WakeUp() would need to write
 131     // to it again.
 132     m_pipeIsEmpty = true;
 133
 134     // writing to the wake up pipe will make wxConsoleEventLoop return from
 135     // wxFDIODispatcher::Dispatch() it might be currently blocking in, nothing
 136     // else needs to be done
 137 }