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::WakeUpNoLock()
  73 {
  74     // No need to do anything if the pipe already contains something.
  75     if ( !m_pipeIsEmpty )
  76       return;
  77
  78     if ( write(m_pipe[wxPipe::Write], "s", 1) != 1 )
  79     {
  80         // don't use wxLog here, we can be in another thread and this could
  81         // result in dead locks
  82         perror("write(wake up pipe)");
  83     }
  84     else
  85     {
  86         // We just wrote to it, so it's not empty any more.
  87         m_pipeIsEmpty = false;
  88     }
  89 }
  90
  91 void wxWakeUpPipe::OnReadWaiting()
  92 {
  93     // got wakeup from child thread, remove the data that provoked it from the
  94     // pipe
  95
  96     char buf[4];
  97     for ( ;; )
  98     {
  99         const int size = read(GetReadFd(), buf, WXSIZEOF(buf));
 100
 101         if ( size > 0 )
 102         {
 103             wxASSERT_MSG( size == 1, "Too many writes to wake-up pipe?" );
 104
 105             break;
 106         }
 107
 108         if ( size == 0 || (size == -1 && errno == EAGAIN) )
 109         {
 110             // No data available, not an error (but still surprising,
 111             // spurious wakeup?)
 112             break;
 113         }
 114
 115         if ( errno == EINTR )
 116         {
 117             // We were interrupted, try again.
 118             continue;
 119         }
 120
 121         wxLogSysError(_("Failed to read from wake-up pipe"));
 122
 123         return;
 124     }
 125
 126     // The pipe is empty now, so future calls to WakeUp() would need to write
 127     // to it again.
 128     m_pipeIsEmpty = true;
 129 }