From a07616d612bebc6324b29d7ab0c9b84d4e9d7c42 Mon Sep 17 00:00:00 2001
From: John Snow
Date: Wed, 15 Sep 2021 12:29:32 -0400
Subject: python/aqmp: add asyncio compatibility wrappers

Python 3.6 does not have all of the goodies that Python 3.7 does, and we
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 <jsnow@redhat.com>
Message-id: 20210915162955.333025-5-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
---
 python/qemu/aqmp/util.py | 89 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 python/qemu/aqmp/util.py

(limited to 'python/qemu/aqmp/util.py')

diff --git a/python/qemu/aqmp/util.py b/python/qemu/aqmp/util.py
new file mode 100644
index 0000000000..28acd995db
--- /dev/null
+++ b/python/qemu/aqmp/util.py
@@ -0,0 +1,89 @@
+"""
+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,
+)
+
+
+T = TypeVar('T')
+
+
+# -------------------------------
+# 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)
+
+    # This is an ugly workaround, but it's the best I can come up with.
+    sock = transport.get_extra_info('socket')
+
+    if sock is None:
+        # Our transport doesn't have a socket? ...
+        # Nothing we can reasonably do.
+        return
+
+    while sock.fileno() != -1:
+        await asyncio.sleep(0)
-- 
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