Telethon/telethon/extensions/messagepacker.py

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import asyncio
import collections
import io
import struct
from ..tl import TLRequest
from ..tl.core.messagecontainer import MessageContainer
from ..tl.core.tlmessage import TLMessage
class MessagePacker:
"""
This class packs `RequestState` as outgoing `TLMessages`.
The purpose of this class is to support putting N `RequestState` into a
queue, and then awaiting for "packed" `TLMessage` in the other end. The
simplest case would be ``State -> TLMessage`` (1-to-1 relationship) but
for efficiency purposes it's ``States -> Container`` (N-to-1).
This addresses several needs: outgoing messages will be smaller, so the
encryption and network overhead also is smaller. It's also a central
point where outgoing requests are put, and where ready-messages are get.
"""
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def __init__(self, state, loggers):
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self._state = state
self._deque = collections.deque()
self._ready = asyncio.Event()
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self._log = loggers[__name__]
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def append(self, state):
self._deque.append(state)
self._ready.set()
def extend(self, states):
self._deque.extend(states)
self._ready.set()
async def get(self):
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"""
Returns (batch, data) if one or more items could be retrieved.
If the cancellation occurs or only invalid items were in the
queue, (None, None) will be returned instead.
"""
if not self._deque:
self._ready.clear()
await self._ready.wait()
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buffer = io.BytesIO()
batch = []
size = 0
# Fill a new batch to return while the size is small enough,
# as long as we don't exceed the maximum length of messages.
while self._deque and len(batch) <= MessageContainer.MAXIMUM_LENGTH:
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state = self._deque.popleft()
size += len(state.data) + TLMessage.SIZE_OVERHEAD
if size <= MessageContainer.MAXIMUM_SIZE:
state.msg_id = self._state.write_data_as_message(
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buffer, state.data, isinstance(state.request, TLRequest),
after_id=state.after.msg_id if state.after else None
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)
batch.append(state)
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self._log.debug('Assigned msg_id = %d to %s (%x)',
state.msg_id, state.request.__class__.__name__,
id(state.request))
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continue
if batch:
# Put the item back since it can't be sent in this batch
self._deque.appendleft(state)
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break
# If a single message exceeds the maximum size, then the
# message payload cannot be sent. Telegram would forcibly
# close the connection; message would never be confirmed.
#
# We don't put the item back because it can never be sent.
# If we did, we would loop again and reach this same path.
# Setting the exception twice results in `InvalidStateError`
# and this method should never return with error, which we
# really want to avoid.
self._log.warning(
'Message payload for %s is too long (%d) and cannot be sent',
state.request.__class__.__name__, len(state.data)
)
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state.future.set_exception(
ValueError('Request payload is too big'))
size = 0
continue
if not batch:
return None, None
if len(batch) > 1:
# Inlined code to pack several messages into a container
data = struct.pack(
'<Ii', MessageContainer.CONSTRUCTOR_ID, len(batch)
) + buffer.getvalue()
buffer = io.BytesIO()
container_id = self._state.write_data_as_message(
buffer, data, content_related=False
)
for s in batch:
s.container_id = container_id
data = buffer.getvalue()
return batch, data