libs/pbd/crossthread.posix.cc

   1 #include <poll.h>
   2
   3 CrossThreadChannel::CrossThreadChannel (bool non_blocking)
   4         : receive_channel (0)
   5         , receive_source (0)
   6 {
   7         fds[0] = -1;
   8         fds[1] = -1;
   9
  10         if (pipe (fds)) {
  11                 error << "cannot create x-thread pipe for read (%2)" << ::strerror (errno) << endmsg;
  12                 return;
  13         }
  14
  15         if (non_blocking) {
  16                 if (fcntl (fds[0], F_SETFL, O_NONBLOCK)) {
  17                         error << "cannot set non-blocking mode for x-thread pipe (read) (" << ::strerror (errno) << ')' << endmsg;
  18                         return;
  19                 }
  20
  21                 if (fcntl (fds[1], F_SETFL, O_NONBLOCK)) {
  22                         error << "cannot set non-blocking mode for x-thread pipe (write) (%2)" << ::strerror (errno) << ')' << endmsg;
  23                         return;
  24                 }
  25         }
  26
  27         receive_channel = g_io_channel_unix_new (fds[0]);
  28 }
  29
  30 CrossThreadChannel::~CrossThreadChannel ()
  31 {
  32         if (receive_source) {
  33                 /* this disconnects it from any main context it was attached in
  34                    in ::attach(), this prevent its callback from being invoked
  35                    after the destructor has finished.
  36                 */
  37                 g_source_destroy (receive_source);
  38         }
  39
  40         if (receive_channel) {
  41                 g_io_channel_unref (receive_channel);
  42                 receive_channel = 0;
  43         }
  44
  45         if (fds[0] >= 0) {
  46                 close (fds[0]);
  47                 fds[0] = -1;
  48         }
  49
  50         if (fds[1] >= 0) {
  51                 close (fds[1]);
  52                 fds[1] = -1;
  53         }
  54 }
  55
  56 void
  57 CrossThreadChannel::wakeup ()
  58 {
  59         char c = 0;
  60         (void) ::write (fds[1], &c, 1);
  61 }
  62
  63 void
  64 CrossThreadChannel::drain ()
  65 {
  66         char buf[64];
  67         while (::read (fds[0], buf, sizeof (buf)) > 0) {};
  68 }
  69
  70 int
  71 CrossThreadChannel::deliver (char msg)
  72 {
  73         return ::write (fds[1], &msg, 1);
  74 }
  75
  76 bool
  77 CrossThreadChannel::poll_for_request()
  78 {
  79         struct pollfd pfd[1];
  80         pfd[0].fd = fds[0];
  81         pfd[0].events = POLLIN|POLLERR|POLLHUP;
  82         while(true) {
  83                 if (poll (pfd, 1, -1) < 0) {
  84                         if (errno == EINTR) {
  85                                 continue;
  86                         }
  87                         break;
  88                 }
  89                 if (pfd[0].revents & ~POLLIN) {
  90                         break;
  91                 }
  92
  93                 if (pfd[0].revents & POLLIN) {
  94                         return true;
  95                 }
  96         }
  97         return false;
  98 }
  99
 100 int
 101 CrossThreadChannel::receive (char& msg, bool wait)
 102 {
 103         if (wait) {
 104                 if (!poll_for_request ()) {
 105                         return -1;
 106                 }
 107         }
 108         return ::read (fds[0], &msg, 1);
 109 }