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                 g_source_destroy (receive_source);
  34                 receive_source = 0;
  35         }
  36
  37         if (receive_channel) {
  38                 g_io_channel_unref (receive_channel);
  39                 receive_channel = 0;
  40         }
  41
  42         if (fds[0] >= 0) {
  43                 close (fds[0]);
  44                 fds[0] = -1;
  45         }
  46
  47         if (fds[1] >= 0) {
  48                 close (fds[1]);
  49                 fds[1] = -1;
  50         }
  51 }
  52
  53 void
  54 CrossThreadChannel::wakeup ()
  55 {
  56         char c = 0;
  57         (void) ::write (fds[1], &c, 1);
  58 }
  59
  60 void
  61 CrossThreadChannel::drain ()
  62 {
  63         char buf[64];
  64         while (::read (fds[0], buf, sizeof (buf)) > 0) {};
  65 }
  66
  67 int
  68 CrossThreadChannel::deliver (char msg)
  69 {
  70         return ::write (fds[1], &msg, 1);
  71 }
  72
  73 bool
  74 CrossThreadChannel::poll_for_request()
  75 {
  76         struct pollfd pfd[1];
  77         pfd[0].fd = fds[0];
  78         pfd[0].events = POLLIN|POLLERR|POLLHUP;
  79         while(true) {
  80                 if (poll (pfd, 1, -1) < 0) {
  81                         if (errno == EINTR) {
  82                                 continue;
  83                         }
  84                         break;
  85                 }
  86                 if (pfd[0].revents & ~POLLIN) {
  87                         break;
  88                 }
  89
  90                 if (pfd[0].revents & POLLIN) {
  91                         return true;
  92                 }
  93         }
  94         return false;
  95 }
  96
  97 int
  98 CrossThreadChannel::receive (char& msg, bool wait)
  99 {
 100         if (wait) {
 101                 if (!poll_for_request ()) {
 102                         return -1;
 103                 }
 104         }
 105         return ::read (fds[0], &msg, 1);
 106 }