asyncio.transports: Make _ProactorBasePipeTransport use _FlowControlMixin
diff --git a/Lib/asyncio/transports.py b/Lib/asyncio/transports.py
index 67ae7fd..5b975aa 100644
--- a/Lib/asyncio/transports.py
+++ b/Lib/asyncio/transports.py
@@ -219,3 +219,73 @@
http://docs.python.org/3/library/subprocess#subprocess.Popen.kill
"""
raise NotImplementedError
+
+
+class _FlowControlMixin(Transport):
+ """All the logic for (write) flow control in a mix-in base class.
+
+ The subclass must implement get_write_buffer_size(). It must call
+ _maybe_pause_protocol() whenever the write buffer size increases,
+ and _maybe_resume_protocol() whenever it decreases. It may also
+ override set_write_buffer_limits() (e.g. to specify different
+ defaults).
+
+ The subclass constructor must call super().__init__(extra). This
+ will call set_write_buffer_limits().
+
+ The user may call set_write_buffer_limits() and
+ get_write_buffer_size(), and their protocol's pause_writing() and
+ resume_writing() may be called.
+ """
+
+ def __init__(self, extra=None):
+ super().__init__(extra)
+ self._protocol_paused = False
+ self.set_write_buffer_limits()
+
+ def _maybe_pause_protocol(self):
+ size = self.get_write_buffer_size()
+ if size <= self._high_water:
+ return
+ if not self._protocol_paused:
+ self._protocol_paused = True
+ try:
+ self._protocol.pause_writing()
+ except Exception as exc:
+ self._loop.call_exception_handler({
+ 'message': 'protocol.pause_writing() failed',
+ 'exception': exc,
+ 'transport': self,
+ 'protocol': self._protocol,
+ })
+
+ def _maybe_resume_protocol(self):
+ if (self._protocol_paused and
+ self.get_write_buffer_size() <= self._low_water):
+ self._protocol_paused = False
+ try:
+ self._protocol.resume_writing()
+ except Exception as exc:
+ self._loop.call_exception_handler({
+ 'message': 'protocol.resume_writing() failed',
+ 'exception': exc,
+ 'transport': self,
+ 'protocol': self._protocol,
+ })
+
+ def set_write_buffer_limits(self, high=None, low=None):
+ if high is None:
+ if low is None:
+ high = 64*1024
+ else:
+ high = 4*low
+ if low is None:
+ low = high // 4
+ if not high >= low >= 0:
+ raise ValueError('high (%r) must be >= low (%r) must be >= 0' %
+ (high, low))
+ self._high_water = high
+ self._low_water = low
+
+ def get_write_buffer_size(self):
+ raise NotImplementedError