async_serial: support for asyncio serial devices

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

moonraker/utils/async_serial.py

@@ -0,0 +1,126 @@
+# Asyncio wrapper for serial communications
+#
+# Copyright (C) 2024 Eric Callahan <arksine.code@gmail.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+from __future__ import annotations
+import os
+import errno
+import logging
+import asyncio
+import contextlib
+from serial import Serial, SerialException
+from typing import TYPE_CHECKING, Optional, List, Tuple, Awaitable
+
+if TYPE_CHECKING:
+    from ..confighelper import ConfigHelper
+
+READER_LIMIT = 4*1024*1024
+
+
+class AsyncSerialConnection:
+    error = SerialException
+    def __init__(self, config: ConfigHelper, default_baud: int = 57600) -> None:
+        self.name = config.get_name()
+        self.eventloop = config.get_server().get_event_loop()
+        self.port: str = config.get("serial")
+        self.baud = config.getint("baud", default_baud)
+        self.ser: Optional[Serial] = None
+        self.send_task: Optional[asyncio.Task] = None
+        self.send_buffer: List[Tuple[asyncio.Future, bytes]] = []
+        self._reader = asyncio.StreamReader(limit=READER_LIMIT)
+
+    @property
+    def connected(self) -> bool:
+        return self.ser is not None
+
+    @property
+    def reader(self) -> asyncio.StreamReader:
+        return self._reader
+
+    def close(self) -> Awaitable:
+        if self.ser is not None:
+            self.eventloop.remove_reader(self.ser.fileno())
+            self.ser.close()
+            logging.info(f"{self.name}: Disconnected")
+        self.ser = None
+        for (fut, _) in self.send_buffer:
+            fut.set_exception(SerialException("Serial Device Closed"))
+        self.send_buffer.clear()
+        self._reader.feed_eof()
+        if self.send_task is not None and not self.send_task.done():
+            async def _cancel_send(send_task: asyncio.Task):
+                with contextlib.suppress(asyncio.TimeoutError):
+                    await asyncio.wait_for(send_task, 2.)
+            return self.eventloop.create_task(_cancel_send(self.send_task))
+        self.send_task = None
+        fut = self.eventloop.create_future()
+        fut.set_result(None)
+        return fut
+
+    def open(self, exclusive: bool = True) -> None:
+        if self.connected:
+            return
+        logging.info(f"{self.name} :Attempting to open serial device: {self.port}")
+        ser = Serial(self.port, self.baud, timeout=0, exclusive=exclusive)
+        self.ser = ser
+        fd = self.ser.fileno()
+        os.set_blocking(fd, False)
+        self.eventloop.add_reader(fd, self._handle_incoming)
+        self._reader = asyncio.StreamReader(limit=READER_LIMIT)
+        logging.info(f"{self.name} Connected")
+
+    def _handle_incoming(self) -> None:
+        # Process incoming data using same method as gcode.py
+        if self.ser is None:
+            return
+        try:
+            data = os.read(self.ser.fileno(), 4096)
+        except OSError:
+            return
+
+        if not data:
+            # possibly an error, disconnect
+            logging.info(f"{self.name}: No data received, disconnecting")
+            self.close()
+        else:
+            self._reader.feed_data(data)
+
+    def send(self, data: bytes) -> asyncio.Future:
+        fut = self.eventloop.create_future()
+        if not self.connected:
+            fut.set_exception(SerialException("Serial Device Closed"))
+            return fut
+        self.send_buffer.append((fut, data))
+        if self.send_task is None or self.send_task.done():
+            self.send_task = self.eventloop.create_task(self._do_send())
+        return fut
+
+    async def _do_send(self) -> None:
+        while self.send_buffer:
+            fut, data = self.send_buffer.pop()
+            while data:
+                if self.ser is None:
+                    sent = 0
+                else:
+                    try:
+                        sent = os.write(self.ser.fileno(), data)
+                    except OSError as e:
+                        if e.errno == errno.EBADF or e.errno == errno.EPIPE:
+                            sent = 0
+                        else:
+                            await asyncio.sleep(.001)
+                            continue
+                if sent:
+                    data = data[sent:]
+                else:
+                    logging.exception(
+                        f"{self.name}: Error writing data, closing serial connection"
+                    )
+                    fut.set_exception(SerialException("Serial Device Closed"))
+                    self.send_task = None
+                    self.close()
+                    return
+            fut.set_result(None)
+        self.send_task = None