[Pkg-mpd-commits] [python-mpd] 50/91: asyncio: Initial support

[Simon McVittie]

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smcv pushed a commit to branch debian/master
in repository python-mpd.

commit dcb2a00f1b5874dc1cebec3e15029c8cc8a80f35
Author: chrysn <chrysn at fsfe.org>
Date:   Thu Apr 6 21:57:10 2017 +0200

    asyncio: Initial support
---
 examples/asyncio_example.py |  31 +++++++++++
 mpd/asyncio.py              | 124 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 155 insertions(+)

diff --git a/examples/asyncio_example.py b/examples/asyncio_example.py
new file mode 100644
index 0000000..39d985d
--- /dev/null
+++ b/examples/asyncio_example.py
@@ -0,0 +1,31 @@
+import asyncio
+
+from mpd.asyncio import MPDClient
+
+async def main():
+    print("Create MPD client")
+    client = MPDClient()
+    try:
+        await client.connect('localhost', 6600)
+    except Exception as e:
+        print("Connection failed:", e)
+        return
+
+    print("Connected to MPD version", client.mpd_version)
+
+    try:
+        status = await client.status()
+    except Exception as e:
+        print("Status error:", e)
+        return
+    else:
+        print("Status success:", status)
+
+    for x in await client.decoders():
+        print("sync decoder:", x)
+
+    async for x in client.decoders():
+        print("async decoder:", x)
+
+if __name__ == '__main__':
+    asyncio.get_event_loop().run_until_complete(main())
diff --git a/mpd/asyncio.py b/mpd/asyncio.py
new file mode 100644
index 0000000..e5ac2cd
--- /dev/null
+++ b/mpd/asyncio.py
@@ -0,0 +1,124 @@
+import asyncio
+
+from mpd.base import HELLO_PREFIX, ERROR_PREFIX, SUCCESS
+from mpd.base import MPDClientBase
+from mpd.base import MPDClient as SyncMPDClient
+from mpd.base import ProtocolError, ConnectionError
+from mpd.base import mpd_command_provider
+
+ at mpd_command_provider
+class MPDClient(MPDClientBase):
+    __run_task = None # doubles as indicator for being connected
+
+    async def connect(self, host, port=6600, loop=None):
+        self.__loop = loop
+
+        if '/' in host:
+            r, w = await asyncio.open_unic_connection(path, loop=loop)
+        else:
+            r, w = await asyncio.open_connection(host, port, loop=loop)
+        self.__rfile, self.__wfile = r, w
+
+        self.__commandqueue = asyncio.Queue(loop=loop)
+
+        await self.__hello()
+
+        self.__run_task = asyncio.Task(self.__run())
+
+    def disconnect(self):
+        self.__run_task.cancel()
+        self.__rfile = self.__wfile = None
+        self.__run_task = self.__commandqueue = None
+
+    async def __run(self):
+        while True:
+            command, args, callback, result = await self.__commandqueue.get()
+            self._write_command(command, args)
+            responselines = await self.__read_full_output()
+            try:
+                result.set_result(callback(self, responselines))
+            except Exception as e:
+                result.set_error(e)
+
+    # helper methods
+
+    async def __readline(self):
+        """Wrapper around .__rfile.readline that handles encoding"""
+        data = await self.__rfile.readline()
+        try:
+            return data.decode('utf8')
+        except UnicodeDecodeError:
+            self.disconnect()
+            raise ProtocolError("Invalid UTF8 received")
+
+    def __write(self, text):
+        """Wrapper around .__wfile.write that handles encoding."""
+        self.__wfile.write(text.encode('utf8'))
+
+    # copied stuff from base
+
+    async def __hello(self):
+        # not catching the timeout error, it's actually pretty adaequate
+        try:
+            line = await asyncio.wait_for(self.__readline(), timeout=5)
+        except asyncio.TimeoutError:
+            self.disconnect()
+            raise ConnectionError("No response from server while reading MPD hello")
+
+        # FIXME this is copied from base.MPDClient._hello
+        if not line.endswith("\n"):
+            self.disconnect()
+            raise ConnectionError("Connection lost while reading MPD hello")
+        line = line.rstrip("\n")
+        if not line.startswith(HELLO_PREFIX):
+            raise ProtocolError("Got invalid MPD hello: '{}'".format(line))
+        self.mpd_version = line[len(HELLO_PREFIX):].strip()
+
+    # FIXME this is just a wrapper for the below
+    def _write_line(self, text):
+        self.__write(text + "\n")
+    # FIXME this code should be sharable
+    _write_command = SyncMPDClient._write_command
+
+
+    async def __read_output_line(self):
+        """Kind of like SyncMPDClient._read_line"""
+        line = await self.__readline()
+        if not line.endswith("\n"):
+            self.disconnect()
+            raise ConnectionError("Connection lost while reading line")
+        line = line.rstrip("\n")
+        if line.startswith(ERROR_PREFIX):
+            error = line[len(ERROR_PREFIX):].strip()
+            raise CommandError(error)
+        if line == SUCCESS:
+            return None
+        return line
+
+    async def __read_full_output(self):
+        """Kind of like SyncMPDClient._read_lines, but without the iteration"""
+        result = []
+        while True:
+            line = await self.__read_output_line()
+            if line is None:
+                return result
+            else:
+                result.append(line)
+
+    # command provider interface
+
+    @classmethod
+    def add_command(cls, name, callback):
+        if hasattr(cls, name):
+            # twisted silently ignores them; probably, i'll make an
+            # experience that'll make me take the same router at some point.
+            raise AttributeError("Refusing to override the %s command"%name)
+        def f(self, *args):
+            result = asyncio.Future()
+            self.__commandqueue.put_nowait(
+                    (name, args, callback, result)
+                    )
+            return result
+        escaped_name = name.replace(" ", "_")
+        f.__name__ = escaped_name
+        setattr(cls, escaped_name, f)

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