Added delete option to database storage.

venv/Lib/site-packages/grpc/framework/foundation/stream_util.py

@@ -0,0 +1,148 @@
+# Copyright 2015 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Helpful utilities related to the stream module."""
+
+import logging
+import threading
+
+from grpc.framework.foundation import stream
+
+_NO_VALUE = object()
+_LOGGER = logging.getLogger(__name__)
+
+
+class TransformingConsumer(stream.Consumer):
+    """A stream.Consumer that passes a transformation of its input to another."""
+
+    def __init__(self, transformation, downstream):
+        self._transformation = transformation
+        self._downstream = downstream
+
+    def consume(self, value):
+        self._downstream.consume(self._transformation(value))
+
+    def terminate(self):
+        self._downstream.terminate()
+
+    def consume_and_terminate(self, value):
+        self._downstream.consume_and_terminate(self._transformation(value))
+
+
+class IterableConsumer(stream.Consumer):
+    """A Consumer that when iterated over emits the values it has consumed."""
+
+    def __init__(self):
+        self._condition = threading.Condition()
+        self._values = []
+        self._active = True
+
+    def consume(self, value):
+        with self._condition:
+            if self._active:
+                self._values.append(value)
+                self._condition.notify()
+
+    def terminate(self):
+        with self._condition:
+            self._active = False
+            self._condition.notify()
+
+    def consume_and_terminate(self, value):
+        with self._condition:
+            if self._active:
+                self._values.append(value)
+                self._active = False
+                self._condition.notify()
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return self.next()
+
+    def next(self):
+        with self._condition:
+            while self._active and not self._values:
+                self._condition.wait()
+            if self._values:
+                return self._values.pop(0)
+            else:
+                raise StopIteration()
+
+
+class ThreadSwitchingConsumer(stream.Consumer):
+    """A Consumer decorator that affords serialization and asynchrony."""
+
+    def __init__(self, sink, pool):
+        self._lock = threading.Lock()
+        self._sink = sink
+        self._pool = pool
+        # True if self._spin has been submitted to the pool to be called once and
+        # that call has not yet returned, False otherwise.
+        self._spinning = False
+        self._values = []
+        self._active = True
+
+    def _spin(self, sink, value, terminate):
+        while True:
+            try:
+                if value is _NO_VALUE:
+                    sink.terminate()
+                elif terminate:
+                    sink.consume_and_terminate(value)
+                else:
+                    sink.consume(value)
+            except Exception as e:  # pylint:disable=broad-except
+                _LOGGER.exception(e)
+
+            with self._lock:
+                if terminate:
+                    self._spinning = False
+                    return
+                elif self._values:
+                    value = self._values.pop(0)
+                    terminate = not self._values and not self._active
+                elif not self._active:
+                    value = _NO_VALUE
+                    terminate = True
+                else:
+                    self._spinning = False
+                    return
+
+    def consume(self, value):
+        with self._lock:
+            if self._active:
+                if self._spinning:
+                    self._values.append(value)
+                else:
+                    self._pool.submit(self._spin, self._sink, value, False)
+                    self._spinning = True
+
+    def terminate(self):
+        with self._lock:
+            if self._active:
+                self._active = False
+                if not self._spinning:
+                    self._pool.submit(self._spin, self._sink, _NO_VALUE, True)
+                    self._spinning = True
+
+    def consume_and_terminate(self, value):
+        with self._lock:
+            if self._active:
+                self._active = False
+                if self._spinning:
+                    self._values.append(value)
+                else:
+                    self._pool.submit(self._spin, self._sink, value, True)
+                    self._spinning = True