Open Media Library Platform

Darwin/lib/python2.7/site-packages/twisted/protocols/pcp.py

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+# -*- test-case-name: twisted.test.test_pcp -*-
+# Copyright (c) Twisted Matrix Laboratories.
+# See LICENSE for details.
+
+"""
+Producer-Consumer Proxy.
+"""
+
+from zope.interface import implements
+
+from twisted.internet import interfaces
+
+
+class BasicProducerConsumerProxy:
+    """
+    I can act as a man in the middle between any Producer and Consumer.
+
+    @ivar producer: the Producer I subscribe to.
+    @type producer: L{IProducer<interfaces.IProducer>}
+    @ivar consumer: the Consumer I publish to.
+    @type consumer: L{IConsumer<interfaces.IConsumer>}
+    @ivar paused: As a Producer, am I paused?
+    @type paused: bool
+    """
+    implements(interfaces.IProducer, interfaces.IConsumer)
+
+    consumer = None
+    producer = None
+    producerIsStreaming = None
+    iAmStreaming = True
+    outstandingPull = False
+    paused = False
+    stopped = False
+
+    def __init__(self, consumer):
+        self._buffer = []
+        if consumer is not None:
+            self.consumer = consumer
+            consumer.registerProducer(self, self.iAmStreaming)
+
+    # Producer methods:
+
+    def pauseProducing(self):
+        self.paused = True
+        if self.producer:
+            self.producer.pauseProducing()
+
+    def resumeProducing(self):
+        self.paused = False
+        if self._buffer:
+            # TODO: Check to see if consumer supports writeSeq.
+            self.consumer.write(''.join(self._buffer))
+            self._buffer[:] = []
+        else:
+            if not self.iAmStreaming:
+                self.outstandingPull = True
+
+        if self.producer is not None:
+            self.producer.resumeProducing()
+
+    def stopProducing(self):
+        if self.producer is not None:
+            self.producer.stopProducing()
+        if self.consumer is not None:
+            del self.consumer
+
+    # Consumer methods:
+
+    def write(self, data):
+        if self.paused or (not self.iAmStreaming and not self.outstandingPull):
+            # We could use that fifo queue here.
+            self._buffer.append(data)
+
+        elif self.consumer is not None:
+            self.consumer.write(data)
+            self.outstandingPull = False
+
+    def finish(self):
+        if self.consumer is not None:
+            self.consumer.finish()
+        self.unregisterProducer()
+
+    def registerProducer(self, producer, streaming):
+        self.producer = producer
+        self.producerIsStreaming = streaming
+
+    def unregisterProducer(self):
+        if self.producer is not None:
+            del self.producer
+            del self.producerIsStreaming
+        if self.consumer:
+            self.consumer.unregisterProducer()
+
+    def __repr__(self):
+        return '<%s@%x around %s>' % (self.__class__, id(self), self.consumer)
+
+
+class ProducerConsumerProxy(BasicProducerConsumerProxy):
+    """ProducerConsumerProxy with a finite buffer.
+
+    When my buffer fills up, I have my parent Producer pause until my buffer
+    has room in it again.
+    """
+    # Copies much from abstract.FileDescriptor
+    bufferSize = 2**2**2**2
+
+    producerPaused = False
+    unregistered = False
+
+    def pauseProducing(self):
+        # Does *not* call up to ProducerConsumerProxy to relay the pause
+        # message through to my parent Producer.
+        self.paused = True
+
+    def resumeProducing(self):
+        self.paused = False
+        if self._buffer:
+            data = ''.join(self._buffer)
+            bytesSent = self._writeSomeData(data)
+            if bytesSent < len(data):
+                unsent = data[bytesSent:]
+                assert not self.iAmStreaming, (
+                    "Streaming producer did not write all its data.")
+                self._buffer[:] = [unsent]
+            else:
+                self._buffer[:] = []
+        else:
+            bytesSent = 0
+
+        if (self.unregistered and bytesSent and not self._buffer and
+            self.consumer is not None):
+            self.consumer.unregisterProducer()
+
+        if not self.iAmStreaming:
+            self.outstandingPull = not bytesSent
+
+        if self.producer is not None:
+            bytesBuffered = sum([len(s) for s in self._buffer])
+            # TODO: You can see here the potential for high and low
+            # watermarks, where bufferSize would be the high mark when we
+            # ask the upstream producer to pause, and we wouldn't have
+            # it resume again until it hit the low mark.  Or if producer
+            # is Pull, maybe we'd like to pull from it as much as necessary
+            # to keep our buffer full to the low mark, so we're never caught
+            # without something to send.
+            if self.producerPaused and (bytesBuffered < self.bufferSize):
+                # Now that our buffer is empty,
+                self.producerPaused = False
+                self.producer.resumeProducing()
+            elif self.outstandingPull:
+                # I did not have any data to write in response to a pull,
+                # so I'd better pull some myself.
+                self.producer.resumeProducing()
+
+    def write(self, data):
+        if self.paused or (not self.iAmStreaming and not self.outstandingPull):
+            # We could use that fifo queue here.
+            self._buffer.append(data)
+
+        elif self.consumer is not None:
+            assert not self._buffer, (
+                "Writing fresh data to consumer before my buffer is empty!")
+            # I'm going to use _writeSomeData here so that there is only one
+            # path to self.consumer.write.  But it doesn't actually make sense,
+            # if I am streaming, for some data to not be all data.  But maybe I
+            # am not streaming, but I am writing here anyway, because there was
+            # an earlier request for data which was not answered.
+            bytesSent = self._writeSomeData(data)
+            self.outstandingPull = False
+            if not bytesSent == len(data):
+                assert not self.iAmStreaming, (
+                    "Streaming producer did not write all its data.")
+                self._buffer.append(data[bytesSent:])
+
+        if (self.producer is not None) and self.producerIsStreaming:
+            bytesBuffered = sum([len(s) for s in self._buffer])
+            if bytesBuffered >= self.bufferSize:
+
+                self.producer.pauseProducing()
+                self.producerPaused = True
+
+    def registerProducer(self, producer, streaming):
+        self.unregistered = False
+        BasicProducerConsumerProxy.registerProducer(self, producer, streaming)
+        if not streaming:
+            producer.resumeProducing()
+
+    def unregisterProducer(self):
+        if self.producer is not None:
+            del self.producer
+            del self.producerIsStreaming
+        self.unregistered = True
+        if self.consumer and not self._buffer:
+            self.consumer.unregisterProducer()
+
+    def _writeSomeData(self, data):
+        """Write as much of this data as possible.
+
+        @returns: The number of bytes written.
+        """
+        if self.consumer is None:
+            return 0
+        self.consumer.write(data)
+        return len(data)