Add chop ability to ReadWriteStream

Also adds tests for read write stream

Author: MatthewScholefield

runner/precise_runner/runner.py

@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import atexit
+
+import time
 from subprocess import PIPE, Popen
 from threading import Thread, Event
 
@@ -72,17 +74,25 @@ def __init__(self, listener, chunk_size=2048):
 
 
 class ReadWriteStream(object):
-    """Class used to support writing binary audio data at any pace"""
-    def __init__(self, s=b''):
+    """
+    Class used to support writing binary audio data at any pace,
+    optionally chopping when the buffer gets too large
+    """
+    def __init__(self, s=b'', chop_samples=-1):
         self.buffer = s
         self.write_event = Event()
+        self.chop_samples = chop_samples
 
     def read(self, n=-1, timeout=None):
         if n == -1:
             n = len(self.buffer)
+        if 0 < self.chop_samples < len(self.buffer):
+            self.buffer = self.buffer[self.chop_samples:]
+        return_time = time.time() + (float('inf') if timeout is None else timeout)
         while len(self.buffer) < n:
             self.write_event.clear()
-            self.write_event.wait(timeout)
+            if not self.write_event.wait(return_time - time.time()):
+                return b''
         chunk = self.buffer[:n]
         self.buffer = self.buffer[n:]
         return chunk

runner/test/test_runner.py

@@ -0,0 +1,18 @@
+from precise_runner import ReadWriteStream
+
+
+class TestReadWriteStream:
+    def test_read_write(self):
+        s = ReadWriteStream(b'1234567890')
+        assert s.read(2) == b'12'
+        assert s.read(2) == b'34'
+        s.write(b'hi')
+        assert s.read() == b'567890hi'
+        s.write(b'hello')
+        assert s.read() == b'hello'
+        assert s.read(1, timeout=0.1) == b''
+
+    def test_chop(self):
+        s = ReadWriteStream(chop_samples=10)
+        s.write(b'1234567890hello')
+        assert s.read(5) == b'hello'