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 // Copyright:   (c) 2013 Vadim Zeitlin <vadim@wxwidgets.org>
   7 // Licence:     wxWindows licence
   8 ///////////////////////////////////////////////////////////////////////////////
   9
  10 // ============================================================================
  11 // declarations
  12 // ============================================================================
  13
  14 // ----------------------------------------------------------------------------
  15 // headers
  16 // ----------------------------------------------------------------------------
  17
  18 // for compilers that support precompilation, includes "wx.h".
  19 #include "wx/wxprec.h"
  20
  21 #ifdef __BORLANDC__
  22     #pragma hdrstop
  23 #endif
  24
  25 #ifndef WX_PRECOMP
  26 #endif // WX_PRECOMP
  27
  28 #include "wx/unix/private/wakeuppipe.h"
  29
  30 #include <errno.h>
  31
  32 // ----------------------------------------------------------------------------
  33 // constants
  34 // ----------------------------------------------------------------------------
  35
  36 #define TRACE_EVENTS wxT("events")
  37
  38 // ============================================================================
  39 // wxWakeUpPipe implementation
  40 // ============================================================================
  41
  42 // ----------------------------------------------------------------------------
  43 // initialization
  44 // ----------------------------------------------------------------------------
  45
  46 wxWakeUpPipe::wxWakeUpPipe()
  47 {
  48     m_pipeIsEmpty = true;
  49
  50     if ( !m_pipe.Create() )
  51     {
  52         wxLogError(_("Failed to create wake up pipe used by event loop."));
  53         return;
  54     }
  55
  56
  57     if ( !m_pipe.MakeNonBlocking(wxPipe::Read) )
  58     {
  59         wxLogSysError(_("Failed to switch wake up pipe to non-blocking mode"));
  60         return;
  61     }
  62
  63     wxLogTrace(TRACE_EVENTS, wxT("Wake up pipe (%d, %d) created"),
  64                m_pipe[wxPipe::Read], m_pipe[wxPipe::Write]);
  65 }
  66
  67 // ----------------------------------------------------------------------------
  68 // wakeup handling
  69 // ----------------------------------------------------------------------------
  70
  71 void wxWakeUpPipe::WakeUpNoLock()
  72 {
  73     // No need to do anything if the pipe already contains something.
  74     if ( !m_pipeIsEmpty )
  75       return;
  76
  77     if ( write(m_pipe[wxPipe::Write], "s", 1) != 1 )
  78     {
  79         // don't use wxLog here, we can be in another thread and this could
  80         // result in dead locks
  81         perror("write(wake up pipe)");
  82     }
  83     else
  84     {
  85         // We just wrote to it, so it's not empty any more.
  86         m_pipeIsEmpty = false;
  87     }
  88 }
  89
  90 void wxWakeUpPipe::OnReadWaiting()
  91 {
  92     // got wakeup from child thread, remove the data that provoked it from the
  93     // pipe
  94
  95     char buf[4];
  96     for ( ;; )
  97     {
  98         const int size = read(GetReadFd(), buf, WXSIZEOF(buf));
  99
 100         if ( size > 0 )
 101         {
 102             wxASSERT_MSG( size == 1, "Too many writes to wake-up pipe?" );
 103
 104             break;
 105         }
 106
 107         if ( size == 0 || (size == -1 && errno == EAGAIN) )
 108         {
 109             // No data available, not an error (but still surprising,
 110             // spurious wakeup?)
 111             break;
 112         }
 113
 114         if ( errno == EINTR )
 115         {
 116             // We were interrupted, try again.
 117             continue;
 118         }
 119
 120         wxLogSysError(_("Failed to read from wake-up pipe"));
 121
 122         return;
 123     }
 124
 125     // The pipe is empty now, so future calls to WakeUp() would need to write
 126     // to it again.
 127     m_pipeIsEmpty = true;
 128 }