Source code for bokeh.protocol.receiver

# Copyright (c) 2012 - 2022, Anaconda, Inc., and Bokeh Contributors.
# All rights reserved.
# The full license is in the file LICENSE.txt, distributed with this software.
''' Assemble WebSocket wire message fragments into complete Bokeh Server
message objects that can be processed.


# Boilerplate
from __future__ import annotations

import logging # isort:skip
log = logging.getLogger(__name__)

# Imports

# Standard library imports
import json
from typing import (

# Bokeh imports
from .exceptions import ValidationError
from .message import BufferHeader, Message

    from typing_extensions import TypeAlias

    from . import Protocol

# Globals and constants

__all__ = (

# General API

# Dev API

Fragment: TypeAlias = Union[str, bytes]

[docs]class Receiver: ''' Receive wire message fragments and assemble complete Bokeh server message objects. On ``MessageError`` or ``ValidationError``, the receiver will reset its state and attempt to consume a new message. The *fragment* received can be either bytes or unicode, depending on the transport's semantics (WebSocket allows both). .. code-block:: python [ # these are required b'{header}', # serialized header dict b'{metadata}', # serialized metadata dict b'{content}, # serialized content dict # these are optional, and come in pairs; header contains num_buffers b'{buf_header}', # serialized buffer header dict b'array' # raw buffer payload data ... ] The ``header`` fragment will have the form: .. code-block:: python header = { # these are required 'msgid' : <str> # a unique id for the message 'msgtype' : <str> # a message type, e.g. 'ACK', 'PATCH-DOC', etc # these are optional 'num_buffers' : <int> # the number of additional buffers, if any } The ``metadata`` fragment may contain any arbitrary information. It is not processed by Bokeh for any purpose, but may be useful for external monitoring or instrumentation tools. The ``content`` fragment is defined by the specific message type. ''' _current_consumer: Callable[[Fragment], None] _fragments: list[Fragment] _message: Message[Any] | None _buf_header: BufferHeader | None _partial: Message[Any] | None
[docs] def __init__(self, protocol: Protocol) -> None: ''' Configure a Receiver with a specific Bokeh protocol. Args: protocol (Protocol) : A Bokeh protocol object to use to assemble collected message fragments. ''' self._protocol = protocol self._current_consumer = self._HEADER self._message = None self._partial = None self._buf_header = None
[docs] async def consume(self, fragment: Fragment) -> Message[Any]|None: ''' Consume individual protocol message fragments. Args: fragment (``JSON``) : A message fragment to assemble. When a complete message is assembled, the receiver state will reset to begin consuming a new message. ''' self._current_consumer(fragment) return self._message
def _HEADER(self, fragment: Fragment) -> None: self._message = None self._partial = None self._fragments = [self._assume_text(fragment)] self._current_consumer = self._METADATA def _METADATA(self, fragment: Fragment) -> None: metadata = self._assume_text(fragment) self._fragments.append(metadata) self._current_consumer = self._CONTENT def _CONTENT(self, fragment: Fragment) -> None: content = self._assume_text(fragment) self._fragments.append(content) header_json, metadata_json, content_json = [self._assume_text(x) for x in self._fragments[:3]] self._partial = self._protocol.assemble(header_json, metadata_json, content_json) self._check_complete() def _BUFFER_HEADER(self, fragment: Fragment) -> None: header = json.loads(self._assume_text(fragment)) if set(header) != { "id" }: raise ValidationError(f"Malformed buffer header {header!r}") self._buf_header = header self._current_consumer = self._BUFFER_PAYLOAD def _BUFFER_PAYLOAD(self, fragment: Fragment) -> None: payload = self._assume_binary(fragment) if self._buf_header is None: raise ValidationError("Consuming a buffer payload, but current buffer header is None") header = BufferHeader(id=self._buf_header["id"]) cast(Message[Any], self._partial).assemble_buffer(header, payload) self._check_complete() def _check_complete(self) -> None: if self._partial and self._partial.complete: self._message = self._partial self._current_consumer = self._HEADER else: self._current_consumer = self._BUFFER_HEADER def _assume_text(self, fragment: Fragment) -> str: if not isinstance(fragment, str): raise ValidationError(f"expected text fragment but received binary fragment for {self._current_consumer.__name__}") return fragment def _assume_binary(self, fragment: Fragment) -> bytes: if not isinstance(fragment, bytes): raise ValidationError(f"expected binary fragment but received text fragment for {self._current_consumer.__name__}") return fragment
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