Buffer: send and receive binary data over Channel

(also some minor fixes in channel)

Examples/Buffer.py

@@ -0,0 +1,323 @@
+##########################################################
+# This RNS example demonstrates how to set up a link to  #
+# a destination, and pass binary data over it using a    #
+# using a channel buffer.                                #
+##########################################################
+from __future__ import annotations
+import os
+import sys
+import time
+import argparse
+from datetime import datetime
+
+import RNS
+from RNS.vendor import umsgpack
+
+# Let's define an app name. We'll use this for all
+# destinations we create. Since this echo example
+# is part of a range of example utilities, we'll put
+# them all within the app namespace "example_utilities"
+APP_NAME = "example_utilities"
+
+
+##########################################################
+#### Server Part #########################################
+##########################################################
+
+# A reference to the latest client link that connected
+latest_client_link = None
+
+# A reference to the latest buffer object
+latest_buffer = None
+
+# This initialisation is executed when the users chooses
+# to run as a server
+def server(configpath):
+    # We must first initialise Reticulum
+    reticulum = RNS.Reticulum(configpath)
+    
+    # Randomly create a new identity for our link example
+    server_identity = RNS.Identity()
+
+    # We create a destination that clients can connect to. We
+    # want clients to create links to this destination, so we
+    # need to create a "single" destination type.
+    server_destination = RNS.Destination(
+        server_identity,
+        RNS.Destination.IN,
+        RNS.Destination.SINGLE,
+        APP_NAME,
+        "bufferexample"
+    )
+
+    # We configure a function that will get called every time
+    # a new client creates a link to this destination.
+    server_destination.set_link_established_callback(client_connected)
+
+    # Everything's ready!
+    # Let's Wait for client requests or user input
+    server_loop(server_destination)
+
+def server_loop(destination):
+    # Let the user know that everything is ready
+    RNS.log(
+        "Link example "+
+        RNS.prettyhexrep(destination.hash)+
+        " running, waiting for a connection."
+    )
+
+    RNS.log("Hit enter to manually send an announce (Ctrl-C to quit)")
+
+    # We enter a loop that runs until the users exits.
+    # If the user hits enter, we will announce our server
+    # destination on the network, which will let clients
+    # know how to create messages directed towards it.
+    while True:
+        entered = input()
+        destination.announce()
+        RNS.log("Sent announce from "+RNS.prettyhexrep(destination.hash))
+
+# When a client establishes a link to our server
+# destination, this function will be called with
+# a reference to the link.
+def client_connected(link):
+    global latest_client_link, latest_buffer
+    latest_client_link = link
+
+    RNS.log("Client connected")
+    link.set_link_closed_callback(client_disconnected)
+
+    # If a new connection is received, the old reader
+    # needs to be disconnected.
+    if latest_buffer:
+        latest_buffer.close()
+
+
+    # Create buffer objects.
+    #   The stream_id parameter to these functions is
+    #   a bit like a file descriptor, except that it
+    #   is unique to the *receiver*.
+    #
+    #   In this example, both the reader and the writer
+    #   use stream_id = 0, but there are actually two
+    #   separate unidirectional streams flowing in
+    #   opposite directions.
+    #
+    channel = link.get_channel()
+    latest_buffer = RNS.Buffer.create_bidirectional_buffer(0, 0, channel, server_buffer_ready)
+
+def client_disconnected(link):
+    RNS.log("Client disconnected")
+
+def server_buffer_ready(ready_bytes: int):
+    """
+    Callback from buffer when buffer has data available
+
+    :param ready_bytes: The number of bytes ready to read
+    """
+    global latest_buffer
+
+    data = latest_buffer.read(ready_bytes)
+    data = data.decode("utf-8")
+
+    RNS.log("Received data on the link: " + data)
+
+    reply_message = "I received \""+data+"\" over the buffer"
+    reply_message = reply_message.encode("utf-8")
+    latest_buffer.write(reply_message)
+    latest_buffer.flush()
+
+
+
+
+##########################################################
+#### Client Part #########################################
+##########################################################
+
+# A reference to the server link
+server_link = None
+
+# A reference to the buffer object, needed to share the
+# object from the link connected callback to the client
+# loop.
+buffer = None
+
+# This initialisation is executed when the users chooses
+# to run as a client
+def client(destination_hexhash, configpath):
+    # We need a binary representation of the destination
+    # hash that was entered on the command line
+    try:
+        dest_len = (RNS.Reticulum.TRUNCATED_HASHLENGTH//8)*2
+        if len(destination_hexhash) != dest_len:
+            raise ValueError(
+                "Destination length is invalid, must be {hex} hexadecimal characters ({byte} bytes).".format(hex=dest_len, byte=dest_len//2)
+            )
+            
+        destination_hash = bytes.fromhex(destination_hexhash)
+    except:
+        RNS.log("Invalid destination entered. Check your input!\n")
+        exit()
+
+    # We must first initialise Reticulum
+    reticulum = RNS.Reticulum(configpath)
+
+    # Check if we know a path to the destination
+    if not RNS.Transport.has_path(destination_hash):
+        RNS.log("Destination is not yet known. Requesting path and waiting for announce to arrive...")
+        RNS.Transport.request_path(destination_hash)
+        while not RNS.Transport.has_path(destination_hash):
+            time.sleep(0.1)
+
+    # Recall the server identity
+    server_identity = RNS.Identity.recall(destination_hash)
+
+    # Inform the user that we'll begin connecting
+    RNS.log("Establishing link with server...")
+
+    # When the server identity is known, we set
+    # up a destination
+    server_destination = RNS.Destination(
+        server_identity,
+        RNS.Destination.OUT,
+        RNS.Destination.SINGLE,
+        APP_NAME,
+        "bufferexample"
+    )
+
+    # And create a link
+    link = RNS.Link(server_destination)
+
+    # We'll also set up functions to inform the
+    # user when the link is established or closed
+    link.set_link_established_callback(link_established)
+    link.set_link_closed_callback(link_closed)
+
+    # Everything is set up, so let's enter a loop
+    # for the user to interact with the example
+    client_loop()
+
+def client_loop():
+    global server_link
+
+    # Wait for the link to become active
+    while not server_link:
+        time.sleep(0.1)
+
+    should_quit = False
+    while not should_quit:
+        try:
+            print("> ", end=" ")
+            text = input()
+
+            # Check if we should quit the example
+            if text == "quit" or text == "q" or text == "exit":
+                should_quit = True
+                server_link.teardown()
+            else:
+                # Otherwise, encode the text and write it to the buffer.
+                text = text.encode("utf-8")
+                buffer.write(text)
+                # Flush the buffer to force the data to be sent.
+                buffer.flush()
+
+
+        except Exception as e:
+            RNS.log("Error while sending data over the link: "+str(e))
+            should_quit = True
+            server_link.teardown()
+
+# This function is called when a link
+# has been established with the server
+def link_established(link):
+    # We store a reference to the link
+    # instance for later use
+    global server_link, buffer
+    server_link = link
+
+    # Create buffer, see server_client_connected() for
+    # more detail about setting up the buffer.
+    channel = link.get_channel()
+    buffer = RNS.Buffer.create_bidirectional_buffer(0, 0, channel, client_buffer_ready)
+
+    # Inform the user that the server is
+    # connected
+    RNS.log("Link established with server, enter some text to send, or \"quit\" to quit")
+
+# When a link is closed, we'll inform the
+# user, and exit the program
+def link_closed(link):
+    if link.teardown_reason == RNS.Link.TIMEOUT:
+        RNS.log("The link timed out, exiting now")
+    elif link.teardown_reason == RNS.Link.DESTINATION_CLOSED:
+        RNS.log("The link was closed by the server, exiting now")
+    else:
+        RNS.log("Link closed, exiting now")
+    
+    RNS.Reticulum.exit_handler()
+    time.sleep(1.5)
+    os._exit(0)
+
+# When the buffer has new data, read it and write it to the terminal.
+def client_buffer_ready(ready_bytes: int):
+    global buffer
+    data = buffer.read(ready_bytes)
+    RNS.log("Received data on the link: " + data.decode("utf-8"))
+    print("> ", end=" ")
+    sys.stdout.flush()
+
+
+##########################################################
+#### Program Startup #####################################
+##########################################################
+
+# This part of the program runs at startup,
+# and parses input of from the user, and then
+# starts up the desired program mode.
+if __name__ == "__main__":
+    try:
+        parser = argparse.ArgumentParser(description="Simple buffer example")
+
+        parser.add_argument(
+            "-s",
+            "--server",
+            action="store_true",
+            help="wait for incoming link requests from clients"
+        )
+
+        parser.add_argument(
+            "--config",
+            action="store",
+            default=None,
+            help="path to alternative Reticulum config directory",
+            type=str
+        )
+
+        parser.add_argument(
+            "destination",
+            nargs="?",
+            default=None,
+            help="hexadecimal hash of the server destination",
+            type=str
+        )
+
+        args = parser.parse_args()
+
+        if args.config:
+            configarg = args.config
+        else:
+            configarg = None
+
+        if args.server:
+            server(configarg)
+        else:
+            if (args.destination == None):
+                print("")
+                parser.print_help()
+                print("")
+            else:
+                client(args.destination, configarg)
+
+    except KeyboardInterrupt:
+        print("")
+        exit()

Examples/Channel.py

@@ -243,11 +243,6 @@ def client(destination_hexhash, configpath):
     # And create a link
     link = RNS.Link(server_destination)
 
-    # We set a callback that will get executed
-    # every time a packet is received over the
-    # link
-    link.set_packet_callback(client_message_received)
-
     # We'll also set up functions to inform the
     # user when the link is established or closed
     link.set_link_established_callback(link_established)
@@ -330,7 +325,7 @@ def link_closed(link):
     time.sleep(1.5)
     os._exit(0)
 
-# When a packet is received over the link, we
+# When a packet is received over the channel, we
 # simply print out the data.
 def client_message_received(message):
     if isinstance(message, StringMessage):
@@ -348,7 +343,7 @@ def client_message_received(message):
 # starts up the desired program mode.
 if __name__ == "__main__":
     try:
-        parser = argparse.ArgumentParser(description="Simple link example")
+        parser = argparse.ArgumentParser(description="Simple channel example")
 
         parser.add_argument(
             "-s",

RNS/Buffer.py

@@ -0,0 +1,305 @@
+from __future__ import annotations
+import sys
+from threading import RLock
+from RNS.vendor import umsgpack
+from RNS.Channel import Channel, MessageBase, SystemMessageTypes
+import RNS
+from io import RawIOBase, BufferedRWPair, BufferedReader, BufferedWriter
+from typing import Callable
+from contextlib import AbstractContextManager
+
+
+class StreamDataMessage(MessageBase):
+    MSGTYPE = SystemMessageTypes.SMT_STREAM_DATA
+    """
+    Message type for ``Channel``. ``StreamDataMessage``
+    uses a system-reserved message type.
+    """
+
+    STREAM_ID_MAX = 65535
+    """
+    While not essential for the current message packing
+    method (umsgpack), the stream id is clamped to the
+    size of a UInt16 for future struct packing.
+    """
+
+    OVERHEAD = 0
+    """
+    The number of bytes used by this messa
+    
+    When the Buffer package is imported, this value is
+    calculated based on the value of RNS.Link.MDU.
+    """
+
+    MAX_DATA_LEN = 0
+    """
+    When the Buffer package is imported, this value is
+    calculcated based on the value of OVERHEAD
+    """
+
+    def __init__(self, stream_id: int = None, data: bytes = None, eof: bool = False):
+        """
+        This class is used to encapsulate binary stream
+        data to be sent over a ``Channel``.
+
+        :param stream_id: id of stream relative to receiver
+        :param data: binary data
+        :param eof: set to True if signalling End of File
+        """
+        super().__init__()
+        if stream_id is not None and stream_id > self.STREAM_ID_MAX:
+            raise ValueError("stream_id must be 0-65535")
+        self.stream_id = stream_id
+        self.data = data or bytes()
+        self.eof = eof
+
+    def pack(self) -> bytes:
+        if self.stream_id is None:
+            raise ValueError("stream_id")
+        return umsgpack.packb((self.stream_id, self.eof, bytes(self.data)))
+
+    def unpack(self, raw):
+        self.stream_id, self.eof, self.data = umsgpack.unpackb(raw)
+
+
+_link_sized_bytes = ("\0"*RNS.Link.MDU).encode("utf-8")
+StreamDataMessage.OVERHEAD = len(StreamDataMessage(stream_id=StreamDataMessage.STREAM_ID_MAX,
+                                                   data=_link_sized_bytes,
+                                                   eof=True).pack()) - len(_link_sized_bytes) - 6  # 6 is envelope overhead
+StreamDataMessage.MAX_DATA_LEN = RNS.Link.MDU - StreamDataMessage.OVERHEAD
+_link_sized_bytes = None
+
+
+class RawChannelReader(RawIOBase, AbstractContextManager):
+    """
+    An implementation of RawIOBase that receives
+    binary stream data sent over a ``Channel``.
+
+      This class generally need not be instantiated directly.
+      Use :func:`RNS.Buffer.create_reader`,
+      :func:`RNS.Buffer.create_writer`, and
+      :func:`RNS.Buffer.create_bidirectional_buffer` functions
+      to create buffered streams with optional callbacks.
+
+      For additional information on the API of this
+      object, see the Python documentation for
+      ``RawIOBase``.
+    """
+    def __init__(self, stream_id: int, channel: Channel):
+        """
+        Create a raw channel reader.
+
+        :param stream_id: local stream id to receive at
+        :param channel: ``Channel`` object to receive from
+        """
+        self._stream_id = stream_id
+        self._channel = channel
+        self._lock = RLock()
+        self._buffer = bytearray()
+        self._eof = False
+        self._channel._register_message_type(StreamDataMessage, is_system_type=True)
+        self._channel.add_message_handler(self._handle_message)
+        self._listeners: [Callable[[int], None]] = []
+
+    def add_ready_callback(self, cb: Callable[[int], None]):
+        """
+        Add a function to be called when new data is available.
+        The function should have the signature ``(ready_bytes: int) -> None``
+
+        :param cb: function to call
+        """
+        with self._lock:
+            self._listeners.append(cb)
+
+    def remove_ready_callback(self, cb: Callable[[int], None]):
+        """
+        Remove a function added with :func:`RNS.RawChannelReader.add_ready_callback()`
+
+        :param cb: function to remove
+        """
+        with self._lock:
+            self._listeners.remove(cb)
+
+    def _handle_message(self, message: MessageBase):
+        if isinstance(message, StreamDataMessage):
+            if message.stream_id == self._stream_id:
+                with self._lock:
+                    if message.data is not None:
+                        self._buffer.extend(message.data)
+                    if message.eof:
+                        self._eof = True
+                    for listener in self._listeners:
+                        try:
+                            listener(len(self._buffer))
+                        except Exception as ex:
+                            RNS.log("Error calling RawChannelReader(" + str(self._stream_id) + ") callback: " + str(ex))
+                    return True
+        return False
+
+    def _read(self, __size: int) -> bytes | None:
+        with self._lock:
+            result = self._buffer[:__size]
+            self._buffer = self._buffer[__size:]
+            return result if len(result) > 0 or self._eof else None
+
+    def readinto(self, __buffer: bytearray) -> int | None:
+        ready = self._read(len(__buffer))
+        if ready:
+            __buffer[:len(ready)] = ready
+        return len(ready) if ready else None
+
+    def writable(self) -> bool:
+        return False
+
+    def seekable(self) -> bool:
+        return False
+
+    def readable(self) -> bool:
+        return True
+
+    def close(self):
+        with self._lock:
+            self._channel.remove_message_handler(self._handle_message)
+            self._listeners.clear()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+        return False
+
+
+class RawChannelWriter(RawIOBase, AbstractContextManager):
+    """
+    An implementation of RawIOBase that receives
+    binary stream data sent over a channel.
+
+      This class generally need not be instantiated directly.
+      Use :func:`RNS.Buffer.create_reader`,
+      :func:`RNS.Buffer.create_writer`, and
+      :func:`RNS.Buffer.create_bidirectional_buffer` functions
+      to create buffered streams with optional callbacks.
+
+      For additional information on the API of this
+      object, see the Python documentation for
+      ``RawIOBase``.
+    """
+    def __init__(self, stream_id: int, channel: Channel):
+        """
+        Create a raw channel writer.
+
+        :param stream_id: remote stream id to sent do
+        :param channel: ``Channel`` object to send on
+        """
+        self._stream_id = stream_id
+        self._channel = channel
+        self._eof = False
+
+    def write(self, __b: bytes) -> int | None:
+        try:
+            if self._channel.is_ready_to_send():
+                chunk = __b[:StreamDataMessage.MAX_DATA_LEN]
+                message = StreamDataMessage(self._stream_id, chunk, self._eof)
+                self._channel.send(message)
+                return len(chunk)
+        except RNS.Channel.ChannelException as cex:
+            if cex.type != RNS.Channel.CEType.ME_LINK_NOT_READY:
+                raise
+        return 0
+
+    def close(self):
+        self._eof = True
+        self.write(bytes())
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+        return False
+
+    def seekable(self) -> bool:
+        return False
+
+    def readable(self) -> bool:
+        return False
+
+    def writable(self) -> bool:
+        return True
+
+class Buffer:
+    """
+    Static functions for creating buffered streams that send
+    and receive over a ``Channel``.
+
+    These functions use ``BufferedReader``, ``BufferedWriter``,
+    and ``BufferedRWPair`` to add buffering to
+    ``RawChannelReader`` and ``RawChannelWriter``.
+    """
+    @staticmethod
+    def create_reader(stream_id: int, channel: Channel,
+                      ready_callback: Callable[[int], None] | None = None) -> BufferedReader:
+        """
+        Create a buffered reader that reads binary data sent
+        over a ``Channel``, with an optional callback when
+        new data is available.
+
+        Callback signature: ``(ready_bytes: int) -> None``
+
+        For more information on the reader-specific functions
+        of this object, see the Python documentation for
+        ``BufferedReader``
+
+        :param stream_id: the local stream id to receive from
+        :param channel: the channel to receive on
+        :param ready_callback: function to call when new data is available
+        :return: a BufferedReader object
+        """
+        reader = RawChannelReader(stream_id, channel)
+        if ready_callback:
+            reader.add_ready_callback(ready_callback)
+        return BufferedReader(reader)
+
+    @staticmethod
+    def create_writer(stream_id: int, channel: Channel) -> BufferedWriter:
+        """
+        Create a buffered writer that writes binary data over
+        a ``Channel``.
+
+        For more information on the writer-specific functions
+        of this object, see the Python documentation for
+        ``BufferedWriter``
+
+        :param stream_id: the remote stream id to send to
+        :param channel: the channel to send on
+        :return: a BufferedWriter object
+        """
+        writer = RawChannelWriter(stream_id, channel)
+        return BufferedWriter(writer)
+
+    @staticmethod
+    def create_bidirectional_buffer(receive_stream_id: int, send_stream_id: int, channel: Channel,
+                                    ready_callback: Callable[[int], None] | None = None) -> BufferedRWPair:
+        """
+        Create a buffered reader/writer pair that reads and
+        writes binary data over a ``Channel``, with an
+        optional callback when new data is available.
+
+        Callback signature: ``(ready_bytes: int) -> None``
+
+        For more information on the reader-specific functions
+        of this object, see the Python documentation for
+        ``BufferedRWPair``
+
+        :param receive_stream_id: the local stream id to receive at
+        :param send_stream_id:  the remote stream id to send to
+        :param channel: the channel to send and receive on
+        :param ready_callback: function to call when new data is available
+        :return: a BufferedRWPair object
+        """
+        reader = RawChannelReader(receive_stream_id, channel)
+        if ready_callback:
+            reader.add_ready_callback(ready_callback)
+        writer = RawChannelWriter(send_stream_id, channel)
+        return BufferedRWPair(reader, writer)

RNS/Channel.py

@@ -34,6 +34,8 @@ import RNS
 from abc import ABC, abstractmethod
 TPacket = TypeVar("TPacket")
 
+class SystemMessageTypes(enum.IntEnum):
+    SMT_STREAM_DATA = 0xff00
 
 class ChannelOutletBase(ABC, Generic[TPacket]):
     """

RNS/__init__.py

@@ -33,6 +33,7 @@ from .Reticulum import Reticulum
 from .Identity import Identity
 from .Link import Link, RequestReceipt
 from .Channel import MessageBase
+from .Buffer import Buffer, RawChannelReader, RawChannelWriter
 from .Transport import Transport
 from .Destination import Destination
 from .Packet import Packet

docs/source/reference.rst

@@ -149,6 +149,48 @@ This chapter lists and explains all classes exposed by the Reticulum Network Sta
 .. autoclass:: RNS.MessageBase()
    :members:
 
+.. _api-buffer:
+
+.. only:: html
+
+   |start-h3| Buffer |end-h3|
+
+.. only:: latex
+
+   Buffer
+   ------
+
+.. autoclass:: RNS.Buffer
+   :members:
+
+.. _api-rawchannelreader:
+
+.. only:: html
+
+   |start-h3| RawChannelReader |end-h3|
+
+.. only:: latex
+
+   RawChannelReader
+   ----------------
+
+.. autoclass:: RNS.RawChannelReader
+   :members: __init__, add_ready_callback, remove_ready_callback
+
+.. _api-rawchannelwriter:
+
+.. only:: html
+
+   |start-h3| RawChannelWriter |end-h3|
+
+.. only:: latex
+
+   RawChannelWriter
+   ----------------
+
+.. autoclass:: RNS.RawChannelWriter
+   :members: __init__
+
 .. _api-transport:
 
 .. only:: html

tests/channel.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 import threading
 import RNS
 from RNS.Channel import MessageState, ChannelOutletBase, Channel, MessageBase
+import RNS.Buffer
 from RNS.vendor import umsgpack
 from typing import Callable
 import contextlib
@@ -91,15 +92,18 @@ class ChannelOutletTest(ChannelOutletBase):
         self._rtt = rtt
         self._usable = True
         self.packets = []
+        self.lock = threading.RLock()
         self.packet_callback: Callable[[ChannelOutletBase, bytes], None] | None = None
 
     def send(self, raw: bytes) -> Packet:
+        with self.lock:
             packet = Packet(raw)
             packet.send()
             self.packets.append(packet)
             return packet
 
     def resend(self, packet: Packet) -> Packet:
+        with self.lock:
             packet.send()
             return packet
 
@@ -370,6 +374,105 @@ class TestChannel(unittest.TestCase):
 
         self.eat_own_dog_food(message, check)
 
+    def test_buffer_small_bidirectional(self):
+        data = "Hello\n"
+        with RNS.Buffer.create_bidirectional_buffer(0, 0, self.h.channel) as buffer:
+            count = buffer.write(data.encode("utf-8"))
+            buffer.flush()
+
+            self.assertEqual(len(data), count)
+            self.assertEqual(1, len(self.h.outlet.packets))
+
+            packet = self.h.outlet.packets[0]
+            self.h.channel._receive(packet.raw)
+            result = buffer.readline()
+
+            self.assertIsNotNone(result)
+            self.assertEqual(len(result), len(data))
+
+            decoded = result.decode("utf-8")
+
+            self.assertEqual(data, decoded)
+
+    def test_buffer_big(self):
+        writer = RNS.Buffer.create_writer(15, self.h.channel)
+        reader = RNS.Buffer.create_reader(15, self.h.channel)
+        data = "01234556789"*1024  # 10 KB
+        count = 0
+        write_finished = False
+
+        def write_thread():
+            nonlocal count, write_finished
+            count = writer.write(data.encode("utf-8"))
+            writer.flush()
+            writer.close()
+            write_finished = True
+        threading.Thread(target=write_thread, name="Write Thread", daemon=True).start()
+
+        while not write_finished or next(filter(lambda x: x.state != MessageState.MSGSTATE_DELIVERED,
+                                                self.h.outlet.packets), None) is not None:
+            with self.h.outlet.lock:
+                for packet in self.h.outlet.packets:
+                    if packet.state != MessageState.MSGSTATE_DELIVERED:
+                        self.h.channel._receive(packet.raw)
+                        packet.delivered()
+            time.sleep(0.0001)
+
+        self.assertEqual(len(data), count)
+
+        read_finished = False
+        result = bytes()
+
+        def read_thread():
+            nonlocal read_finished, result
+            result = reader.read()
+            read_finished = True
+        threading.Thread(target=read_thread, name="Read Thread", daemon=True).start()
+
+        timeout_at = time.time() + 7
+        while not read_finished and time.time() < timeout_at:
+            time.sleep(0.001)
+
+        self.assertTrue(read_finished)
+        self.assertEqual(len(data), len(result))
+
+        decoded = result.decode("utf-8")
+
+        self.assertSequenceEqual(data, decoded)
+
+    def test_buffer_small_with_callback(self):
+        callbacks = 0
+        last_cb_value = None
+
+        def callback(ready: int):
+            nonlocal callbacks, last_cb_value
+            callbacks += 1
+            last_cb_value = ready
+
+        data = "Hello\n"
+        with RNS.RawChannelWriter(0, self.h.channel) as writer, RNS.RawChannelReader(0, self.h.channel) as reader:
+            reader.add_ready_callback(callback)
+            count = writer.write(data.encode("utf-8"))
+            writer.flush()
+
+            self.assertEqual(len(data), count)
+            self.assertEqual(1, len(self.h.outlet.packets))
+
+            packet = self.h.outlet.packets[0]
+            self.h.channel._receive(packet.raw)
+
+            self.assertEqual(1, callbacks)
+            self.assertEqual(len(data), last_cb_value)
+
+            result = reader.readline()
+
+            self.assertIsNotNone(result)
+            self.assertEqual(len(result), len(data))
+
+            decoded = result.decode("utf-8")
+
+            self.assertEqual(data, decoded)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)

tests/link.py

@@ -396,6 +396,48 @@ class TestLink(unittest.TestCase):
         self.assertEqual(l1.status, RNS.Link.CLOSED)
         self.assertEqual(0, len(l1._channel._rx_ring))
 
+    def test_11_buffer_round_trip(self):
+        global c_rns
+        init_rns(self)
+        print("")
+        print("Buffer round trip test")
+
+        # TODO: Load this from public bytes only
+        id1 = RNS.Identity.from_bytes(bytes.fromhex(fixed_keys[0][0]))
+        self.assertEqual(id1.hash, bytes.fromhex(fixed_keys[0][1]))
+
+        dest = RNS.Destination(id1, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "link", "establish")
+
+        self.assertEqual(dest.hash, bytes.fromhex("fb48da0e82e6e01ba0c014513f74540d"))
+
+        l1 = RNS.Link(dest)
+        time.sleep(1)
+        self.assertEqual(l1.status, RNS.Link.ACTIVE)
+        buffer = None
+
+        received = []
+        def handle_data(ready_bytes: int):
+            data = buffer.read(ready_bytes)
+            received.append(data)
+
+        channel = l1.get_channel()
+        buffer = RNS.Buffer.create_bidirectional_buffer(0, 0, channel, handle_data)
+
+        buffer.write("Hi there".encode("utf-8"))
+        buffer.flush()
+
+        time.sleep(0.5)
+
+        self.assertEqual(1 , len(received))
+
+        rx_message = received[0].decode("utf-8")
+
+        self.assertEqual("Hi there back at you", rx_message)
+
+        l1.teardown()
+        time.sleep(0.5)
+        self.assertEqual(l1.status, RNS.Link.CLOSED)
+
 
     def size_str(self, num, suffix='B'):
         units = ['','K','M','G','T','P','E','Z']
@@ -462,6 +504,15 @@ def targets(yp=False):
         channel.register_message_type(MessageTest)
         channel.add_message_handler(handle_message)
 
+        buffer = None
+
+        def handle_buffer(ready_bytes: int):
+            data = buffer.read(ready_bytes)
+            buffer.write((data.decode("utf-8") + " back at you").encode("utf-8"))
+            buffer.flush()
+
+        buffer = RNS.Buffer.create_bidirectional_buffer(0, 0, channel, handle_buffer)
+
     m_rns = RNS.Reticulum("./tests/rnsconfig")
     id1 = RNS.Identity.from_bytes(bytes.fromhex(fixed_keys[0][0]))
     d1 = RNS.Destination(id1, RNS.Destination.IN, RNS.Destination.SINGLE, APP_NAME, "link", "establish")