1 files changed, 294 insertions, 0 deletions
diff --git a/Lib/asyncio/transports.py b/Lib/asyncio/transports.py
new file mode 100644
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--- /dev/null
+++ b/Lib/asyncio/transports.py
@@ -0,0 +1,294 @@
+"""Abstract Transport class."""
+
+from asyncio import compat
+
+__all__ = ['BaseTransport', 'ReadTransport', 'WriteTransport',
+           'Transport', 'DatagramTransport', 'SubprocessTransport',
+           ]
+
+
+class BaseTransport:
+    """Base class for transports."""
+
+    def __init__(self, extra=None):
+        if extra is None:
+            extra = {}
+        self._extra = extra
+
+    def get_extra_info(self, name, default=None):
+        """Get optional transport information."""
+        return self._extra.get(name, default)
+
+    def close(self):
+        """Close the transport.
+
+        Buffered data will be flushed asynchronously.  No more data
+        will be received.  After all buffered data is flushed, the
+        protocol's connection_lost() method will (eventually) called
+        with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class ReadTransport(BaseTransport):
+    """Interface for read-only transports."""
+
+    def pause_reading(self):
+        """Pause the receiving end.
+
+        No data will be passed to the protocol's data_received()
+        method until resume_reading() is called.
+        """
+        raise NotImplementedError
+
+    def resume_reading(self):
+        """Resume the receiving end.
+
+        Data received will once again be passed to the protocol's
+        data_received() method.
+        """
+        raise NotImplementedError
+
+
+class WriteTransport(BaseTransport):
+    """Interface for write-only transports."""
+
+    def set_write_buffer_limits(self, high=None, low=None):
+        """Set the high- and low-water limits for write flow control.
+
+        These two values control when to call the protocol's
+        pause_writing() and resume_writing() methods.  If specified,
+        the low-water limit must be less than or equal to the
+        high-water limit.  Neither value can be negative.
+
+        The defaults are implementation-specific.  If only the
+        high-water limit is given, the low-water limit defaults to a
+        implementation-specific value less than or equal to the
+        high-water limit.  Setting high to zero forces low to zero as
+        well, and causes pause_writing() to be called whenever the
+        buffer becomes non-empty.  Setting low to zero causes
+        resume_writing() to be called only once the buffer is empty.
+        Use of zero for either limit is generally sub-optimal as it
+        reduces opportunities for doing I/O and computation
+        concurrently.
+        """
+        raise NotImplementedError
+
+    def get_write_buffer_size(self):
+        """Return the current size of the write buffer."""
+        raise NotImplementedError
+
+    def write(self, data):
+        """Write some data bytes to the transport.
+
+        This does not block; it buffers the data and arranges for it
+        to be sent out asynchronously.
+        """
+        raise NotImplementedError
+
+    def writelines(self, list_of_data):
+        """Write a list (or any iterable) of data bytes to the transport.
+
+        The default implementation concatenates the arguments and
+        calls write() on the result.
+        """
+        data = compat.flatten_list_bytes(list_of_data)
+        self.write(data)
+
+    def write_eof(self):
+        """Close the write end after flushing buffered data.
+
+        (This is like typing ^D into a UNIX program reading from stdin.)
+
+        Data may still be received.
+        """
+        raise NotImplementedError
+
+    def can_write_eof(self):
+        """Return True if this transport supports write_eof(), False if not."""
+        raise NotImplementedError
+
+    def abort(self):
+        """Close the transport immediately.
+
+        Buffered data will be lost.  No more data will be received.
+        The protocol's connection_lost() method will (eventually) be
+        called with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class Transport(ReadTransport, WriteTransport):
+    """Interface representing a bidirectional transport.
+
+    There may be several implementations, but typically, the user does
+    not implement new transports; rather, the platform provides some
+    useful transports that are implemented using the platform's best
+    practices.
+
+    The user never instantiates a transport directly; they call a
+    utility function, passing it a protocol factory and other
+    information necessary to create the transport and protocol.  (E.g.
+    EventLoop.create_connection() or EventLoop.create_server().)
+
+    The utility function will asynchronously create a transport and a
+    protocol and hook them up by calling the protocol's
+    connection_made() method, passing it the transport.
+
+    The implementation here raises NotImplemented for every method
+    except writelines(), which calls write() in a loop.
+    """
+
+
+class DatagramTransport(BaseTransport):
+    """Interface for datagram (UDP) transports."""
+
+    def sendto(self, data, addr=None):
+        """Send data to the transport.
+
+        This does not block; it buffers the data and arranges for it
+        to be sent out asynchronously.
+        addr is target socket address.
+        If addr is None use target address pointed on transport creation.
+        """
+        raise NotImplementedError
+
+    def abort(self):
+        """Close the transport immediately.
+
+        Buffered data will be lost.  No more data will be received.
+        The protocol's connection_lost() method will (eventually) be
+        called with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class SubprocessTransport(BaseTransport):
+
+    def get_pid(self):
+        """Get subprocess id."""
+        raise NotImplementedError
+
+    def get_returncode(self):
+        """Get subprocess returncode.
+
+        See also
+        http://docs.python.org/3/library/subprocess#subprocess.Popen.returncode
+        """
+        raise NotImplementedError
+
+    def get_pipe_transport(self, fd):
+        """Get transport for pipe with number fd."""
+        raise NotImplementedError
+
+    def send_signal(self, signal):
+        """Send signal to subprocess.
+
+        See also:
+        docs.python.org/3/library/subprocess#subprocess.Popen.send_signal
+        """
+        raise NotImplementedError
+
+    def terminate(self):
+        """Stop the subprocess.
+
+        Alias for close() method.
+
+        On Posix OSs the method sends SIGTERM to the subprocess.
+        On Windows the Win32 API function TerminateProcess()
+         is called to stop the subprocess.
+
+        See also:
+        http://docs.python.org/3/library/subprocess#subprocess.Popen.terminate
+        """
+        raise NotImplementedError
+
+    def kill(self):
+        """Kill the subprocess.
+
+        On Posix OSs the function sends SIGKILL to the subprocess.
+        On Windows kill() is an alias for terminate().
+
+        See also:
+        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, loop=None):
+        super().__init__(extra)
+        assert loop is not None
+        self._loop = loop
+        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 get_write_buffer_limits(self):
+        return (self._low_water, self._high_water)
+
+    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 set_write_buffer_limits(self, high=None, low=None):
+        self._set_write_buffer_limits(high=high, low=low)
+        self._maybe_pause_protocol()
+
+    def get_write_buffer_size(self):
+        raise NotImplementedError