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_channel) {
  33                 g_io_channel_unref (receive_channel);
  34                 receive_channel = 0;
  35         }
  36
  37         if (fds[0] >= 0) {
  38                 close (fds[0]);
  39                 fds[0] = -1;
  40         }
  41
  42         if (fds[1] >= 0) {
  43                 close (fds[1]);
  44                 fds[1] = -1;
  45         }
  46 }
  47
  48 void
  49 CrossThreadChannel::wakeup ()
  50 {
  51         char c = 0;
  52         (void) ::write (fds[1], &c, 1);
  53 }
  54
  55 void
  56 CrossThreadChannel::drain ()
  57 {
  58         char buf[64];
  59         while (::read (fds[0], buf, sizeof (buf)) > 0) {};
  60 }
  61
  62 int
  63 CrossThreadChannel::deliver (char msg)
  64 {
  65         return ::write (fds[1], &msg, 1);
  66 }
  67
  68 bool
  69 CrossThreadChannel::poll_for_request()
  70 {
  71         struct pollfd pfd[1];
  72         pfd[0].fd = fds[0];
  73         pfd[0].events = POLLIN|POLLERR|POLLHUP;
  74         while(true) {
  75                 if (poll (pfd, 1, -1) < 0) {
  76                         if (errno == EINTR) {
  77                                 continue;
  78                         }
  79                         break;
  80                 }
  81                 if (pfd[0].revents & ~POLLIN) {
  82                         break;
  83                 }
  84
  85                 if (pfd[0].revents & POLLIN) {
  86                         return true;
  87                 }
  88         }
  89         return false;
  90 }
  91
  92 int
  93 CrossThreadChannel::receive (char& msg, bool wait)
  94 {
  95         if (wait) {
  96                 if (!poll_for_request ()) {
  97                         return -1;
  98                 }
  99         }
 100         return ::read (fds[0], &msg, 1);
 101 }