amqtt/hbmqtt/adapters.py

# Copyright (c) 2015 Nicolas JOUANIN
#
# See the file license.txt for copying permission.

import io
from websockets.protocol import WebSocketCommonProtocol
from websockets.exceptions import ConnectionClosed
from asyncio import StreamReader, StreamWriter
import logging


class ReaderAdapter:
    """
    Base class for all network protocol reader adapter.

    Reader adapters are used to adapt read operations on the network depending on the
    protocol used
    """

    async def read(self, n=-1) -> bytes:
        """
        Read up to n bytes. If n is not provided, or set to -1, read until EOF and
        return all read bytes. If the EOF was received and the internal buffer is
        empty, return an empty bytes object. :return: packet read as bytes data
        """

    def feed_eof(self):
        """
        Acknowledge EOF
        """


class WriterAdapter:
    """
    Base class for all network protocol writer adapter.

    Writer adapters are used to adapt write operations on the network depending on
    the protocol used
    """

    def write(self, data):
        """
        write some data to the protocol layer
        """

    async def drain(self):
        """
        Let the write buffer of the underlying transport a chance to be flushed.
        """

    def get_peer_info(self):
        """
        Return peer socket info (remote address and remote port as tuple
        """

    async def close(self):
        """
        Close the protocol connection
        """


class WebSocketsReader(ReaderAdapter):
    """
    WebSockets API reader adapter
    This adapter relies on WebSocketCommonProtocol to read from a WebSocket.
    """

    def __init__(self, protocol: WebSocketCommonProtocol):
        self._protocol = protocol
        self._stream = io.BytesIO(b"")

    async def read(self, n=-1) -> bytes:
        await self._feed_buffer(n)
        data = self._stream.read(n)
        return data

    async def _feed_buffer(self, n=1):
        """
        Feed the data buffer by reading a Websocket message.
        :param n: if given, feed buffer until it contains at least n bytes
        """
        buffer = bytearray(self._stream.read())
        while len(buffer) < n:
            try:
                message = await self._protocol.recv()
            except ConnectionClosed:
                message = None
            if message is None:
                break
            if not isinstance(message, bytes):
                raise TypeError("message must be bytes")
            buffer.extend(message)
        self._stream = io.BytesIO(buffer)


class WebSocketsWriter(WriterAdapter):
    """
    WebSockets API writer adapter
    This adapter relies on WebSocketCommonProtocol to read from a WebSocket.
    """

    def __init__(self, protocol: WebSocketCommonProtocol):
        self._protocol = protocol
        self._stream = io.BytesIO(b"")

    def write(self, data):
        """
        write some data to the protocol layer
        """
        self._stream.write(data)

    async def drain(self):
        """
        Let the write buffer of the underlying transport a chance to be flushed.
        """
        data = self._stream.getvalue()
        if len(data):
            await self._protocol.send(data)
        self._stream = io.BytesIO(b"")

    def get_peer_info(self):
        # remote_address can be either a 4-tuple or 2-tuple depending on whether
        # it is an IPv6 or IPv4 address, so we take their shared (host, port)
        # prefix here to present a uniform return value.
        return self._protocol.remote_address[:2]

    async def close(self):
        await self._protocol.close()


class StreamReaderAdapter(ReaderAdapter):
    """
    Asyncio Streams API protocol adapter
    This adapter relies on StreamReader to read from a TCP socket.
    Because API is very close, this class is trivial
    """

    def __init__(self, reader: StreamReader):
        self._reader = reader

    async def read(self, n=-1) -> bytes:
        if n == -1:
            data = await self._reader.read(n)
        else:
            data = await self._reader.readexactly(n)
        return data

    def feed_eof(self):
        return self._reader.feed_eof()


class StreamWriterAdapter(WriterAdapter):
    """
    Asyncio Streams API protocol adapter
    This adapter relies on StreamWriter to write to a TCP socket.
    Because API is very close, this class is trivial
    """

    def __init__(self, writer: StreamWriter):
        self.logger = logging.getLogger(__name__)
        self._writer = writer
        self.is_closed = False  # StreamWriter has no test for closed...we use our own

    def write(self, data):
        if not self.is_closed:
            self._writer.write(data)

    async def drain(self):
        if not self.is_closed:
            await self._writer.drain()

    def get_peer_info(self):
        extra_info = self._writer.get_extra_info("peername")
        return extra_info[0], extra_info[1]

    async def close(self):
        if not self.is_closed:
            self.is_closed = True  # we first mark this closed so yields below don't cause races with waiting writes
            await self._writer.drain()
            if self._writer.can_write_eof():
                self._writer.write_eof()
            self._writer.close()
            try:
                await self._writer.wait_closed()  # py37+
            except AttributeError:
                pass


class BufferReader(ReaderAdapter):
    """
    Byte Buffer reader adapter
    This adapter simply adapt reading a byte buffer.
    """

    def __init__(self, buffer: bytes):
        self._stream = io.BytesIO(buffer)

    async def read(self, n=-1) -> bytes:
        return self._stream.read(n)


class BufferWriter(WriterAdapter):
    """
    ByteBuffer writer adapter
    This adapter simply adapt writing to a byte buffer
    """

    def __init__(self, buffer=b""):
        self._stream = io.BytesIO(buffer)

    def write(self, data):
        """
        write some data to the protocol layer
        """
        self._stream.write(data)

    async def drain(self):
        pass

    def get_buffer(self):
        return self._stream.getvalue()

    def get_peer_info(self):
        return "BufferWriter", 0

    async def close(self):
        self._stream.close()