Python 3.6 does not have all of the goodies that Python 3.7 does, and I
need to support both. Add some compatibility wrappers needed for this
purpose.
(Note: Python 3.6 is EOL December 2021.)
Signed-off-by: John Snow <js...@redhat.com>
---
python/qemu/aqmp/util.py | 106 +++++++++++++++++++++++++++++++++++++++
1 file changed, 106 insertions(+)
create mode 100644 python/qemu/aqmp/util.py
diff --git a/python/qemu/aqmp/util.py b/python/qemu/aqmp/util.py
new file mode 100644
index 00000000000..7e7c2584d2b
--- /dev/null
+++ b/python/qemu/aqmp/util.py
@@ -0,0 +1,106 @@
+"""
+Miscellaneous Utilities
+
+This module provides asyncio utilities and compatibility wrappers for
+Python 3.6 to provide some features that otherwise become available in
+Python 3.7+.
+"""
+
+import asyncio
+import sys
+from typing import (
+ Any,
+ Coroutine,
+ Optional,
+ TypeVar,
+ cast,
+)
+
+
+T = TypeVar('T')
+
+
+# --------------------------
+# Section: Utility Functions
+# --------------------------
+
+
+async def flush(writer: asyncio.StreamWriter) -> None:
+ """
+ Utility function to ensure a StreamWriter is *fully* drained.
+
+ `asyncio.StreamWriter.drain` only promises we will return to below
+ the "high-water mark". This function ensures we flush the entire
+ buffer -- by setting the high water mark to 0 and then calling
+ drain. The flow control limits are restored after the call is
+ completed.
+ """
+ transport = cast(asyncio.WriteTransport, writer.transport)
+
+ # https://github.com/python/typeshed/issues/5779
+ low, high = transport.get_write_buffer_limits() # type: ignore
+ transport.set_write_buffer_limits(0, 0)
+ try:
+ await writer.drain()
+ finally:
+ transport.set_write_buffer_limits(high, low)
+
+
+# -------------------------------
+# Section: Compatibility Wrappers
+# -------------------------------
+
+
+def create_task(coro: Coroutine[Any, Any, T],
+ loop: Optional[asyncio.AbstractEventLoop] = None
+ ) -> 'asyncio.Future[T]':
+ """
+ Python 3.6-compatible `asyncio.create_task` wrapper.
+
+ :param coro: The coroutine to execute in a task.
+ :param loop: Optionally, the loop to create the task in.
+
+ :return: An `asyncio.Future` object.
+ """
+ if sys.version_info >= (3, 7):
+ if loop is not None:
+ return loop.create_task(coro)
+ return asyncio.create_task(coro) # pylint: disable=no-member
+
+ # Python 3.6:
+ return asyncio.ensure_future(coro, loop=loop)
+
+
+def is_closing(writer: asyncio.StreamWriter) -> bool:
+ """
+ Python 3.6-compatible `asyncio.StreamWriter.is_closing` wrapper.
+
+ :param writer: The `asyncio.StreamWriter` object.
+ :return: `True` if the writer is closing, or closed.
+ """
+ if sys.version_info >= (3, 7):
+ return writer.is_closing()
+
+ # Python 3.6:
+ transport = writer.transport
+ assert isinstance(transport, asyncio.WriteTransport)
+ return transport.is_closing()
+
+
+async def wait_closed(writer: asyncio.StreamWriter) -> None:
+ """
+ Python 3.6-compatible `asyncio.StreamWriter.wait_closed` wrapper.
+
+ :param writer: The `asyncio.StreamWriter` to wait on.
+ """
+ if sys.version_info >= (3, 7):
+ await writer.wait_closed()
+ return
+
+ # Python 3.6
+ transport = writer.transport
+ assert isinstance(transport, asyncio.WriteTransport)
+
+ while not transport.is_closing():
+ await asyncio.sleep(0)
+ await flush(writer)
--
2.31.1
