add xrun handling to the examples

it's very primitive, but it shows adequately what can happen and what to
do about it minimally (that is, complain and move on).

isine.py

@@ -84,7 +84,8 @@ class SinePlayer(Thread):
             except Empty:
                 pass
             if buffer:
-                self.device.write(buffer)
+                if self.device.write(buffer) < 0:
+                    print("Playback buffer underrun! Continuing nonetheless ...")
                 
 
 isine = SinePlayer()

playbacktest.py

@@ -47,7 +47,8 @@ if __name__ == '__main__':
     # Read data from stdin
     data = f.read(320)
     while data:
-        out.write(data)
+        if out.write(data) < 0:
+            print("Playback buffer underrun! Continuing nonetheless ...")
         data = f.read(320)
     out.close()
         

playwav.py

@@ -39,7 +39,8 @@ def play(device, f):
 	data = f.readframes(periodsize)
 	while data:
 		# Read data from stdin
-		device.write(data)
+		if device.write(data) < 0:
+			print("Playback buffer underrun! Continuing nonetheless ...")
 		data = f.readframes(periodsize)
 
 

recordtest.py

@@ -59,6 +59,8 @@ if __name__ == '__main__':
 		# Read data from device
 		l, data = inp.read()
 
-		if l:
+		if l < 0:
+			print("Capture buffer overrun! Continuing nonetheless ...")
+		elif l:
 			f.write(data)
 			time.sleep(.001)