Use select() for input and output

1 files changed, 39 insertions, 4 deletions

diff --git a/alsa.cpp b/alsa.cpp
index 9aca9be..d9d7cf9 100644
--- a/alsa.cpp
+++ b/alsa.cpp
@@ -8,7 +8,10 @@
 #include <limits>
 #include <exception>
 #include <stdexcept>
+
 #include <stdio.h>
+#include <sys/types.h>
+#include <sys/time.h>
 
 using namespace std::string_literals;
 
@@ -100,7 +103,9 @@ public:
      throw std::runtime_error("PCM could not be started");
     }
 
-    std::cout << "Info: " << std::to_string(npfd) << " poll fds for pcm" << std::endl;
+    if (npfd != 1) {
+      std::cout << "Warning: " << std::to_string(npfd) << " poll fds for pcm" << std::endl;
+    }
   }
 
   ~PCM()
@@ -114,6 +119,11 @@ public:
     free(pfd);
   }
 
+  int fd()
+  {
+    return pfd->fd;
+  }
+
   // write from buffer to ALSA PCM
   void write()
   {
@@ -204,7 +214,7 @@ public:
     snd_seq_port_subscribe_set_sender(subs, &sender);
     snd_seq_port_subscribe_set_dest(subs, &dest);
     snd_seq_port_subscribe_set_queue(subs, 1);
-    snd_seq_port_subscribe_set_time_update(subs, 1);
+    //snd_seq_port_subscribe_set_time_update(subs, 1);
     snd_seq_port_subscribe_set_time_real(subs, 1);
     // TODO: fix timestamp (currently always 0)
     if (0 > snd_seq_subscribe_port(seq_handle, subs))
@@ -227,7 +237,9 @@ public:
       throw std::runtime_error("snd_seq_poll_descriptors() failure");
     }
 
-    std::cout << "Info: " << std::to_string(npfd) << " poll fds for MIDI" << std::endl;
+    if (npfd != 1) {
+      std::cout << "Warning: " << std::to_string(npfd) << " poll fds for MIDI" << std::endl;
+    }
   }
 
   ~MIDI()
@@ -235,6 +247,11 @@ public:
     free(pfd);
   }
 
+  int fd()
+  {
+    return pfd->fd;
+  }
+
   bool event_ready()
   {
     int result = snd_seq_event_input_pending(seq_handle, 1);
@@ -324,8 +341,26 @@ int main(void)
     stream.generate();
 
     while (true) {
-      midi.wait_for_event();
+      //midi.wait_for_event();
       //pcm.wait_for_event();
+      fd_set read_set;
+      FD_ZERO(&read_set);
+      FD_SET(midi.fd(), &read_set);
+
+      fd_set write_set;
+      FD_ZERO(&write_set);
+      FD_SET(pcm.fd(), &write_set);
+
+      struct timeval timeout;
+      timeout.tv_sec = 1;
+      timeout.tv_usec = 0;
+
+      int result = select(FD_SETSIZE, &read_set, &write_set, NULL, &timeout);
+      if (result < 0) {
+        throw std::runtime_error("select() failed");
+      } else if (result == 0) {
+        throw std::runtime_error("select() timeout");
+      }
 
       if (midi.event_ready())
       {