libs/pbd/crossthread.posix.cc

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