From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39746C433EF for ; Wed, 15 Sep 2021 16:46:00 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CE68D60FC0 for ; Wed, 15 Sep 2021 16:45:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org CE68D60FC0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:46122 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mQY2o-0006fV-La for qemu-devel@archiver.kernel.org; Wed, 15 Sep 2021 12:45:58 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59864) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQXoi-0004Si-RT for qemu-devel@nongnu.org; Wed, 15 Sep 2021 12:31:24 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:57123) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQXod-00050G-RX for qemu-devel@nongnu.org; Wed, 15 Sep 2021 12:31:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631723479; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=X3ZdB6zVPOaC5MPl+Q5FhyNGt37ubCDpIGjI5YszfCE=; b=BD6VkepLSmJx2diVGo56dskfPb81i5D09+qt/HA7EnN8HOU0uPP66cFPSyZTmXwSoebZb7 eW85pqHQ8+nl/0j3GWcQoHu0gVkdR2bcEnkGczT12ObQnsGFVSafOGK52prgAMx+E8itoN PGtxuotRg80KcRLGs7ds2e0E7frkMHE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-217-5pX12LYUO2qtq-SLxYD-jg-1; Wed, 15 Sep 2021 12:31:17 -0400 X-MC-Unique: 5pX12LYUO2qtq-SLxYD-jg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A25369126D; Wed, 15 Sep 2021 16:31:16 +0000 (UTC) Received: from scv.redhat.com (unknown [10.22.11.132]) by smtp.corp.redhat.com (Postfix) with ESMTP id 172D17771A; Wed, 15 Sep 2021 16:31:15 +0000 (UTC) From: John Snow To: qemu-devel@nongnu.org Subject: [PATCH v4 13/27] python/aqmp: add QMP Message format Date: Wed, 15 Sep 2021 12:29:41 -0400 Message-Id: <20210915162955.333025-14-jsnow@redhat.com> In-Reply-To: <20210915162955.333025-1-jsnow@redhat.com> References: <20210915162955.333025-1-jsnow@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" Received-SPF: pass client-ip=216.205.24.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.39, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , Eric Blake , Stefan Hajnoczi , Markus Armbruster , Wainer dos Santos Moschetta , "Niteesh G . S ." , Willian Rampazzo , Cleber Rosa , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The Message class is here primarily to serve as a solid type to use for mypy static typing for unambiguous annotation and documentation. We can also stuff JSON serialization and deserialization into this class itself so it can be re-used even outside this infrastructure. Signed-off-by: John Snow Reviewed-by: Eric Blake --- python/qemu/aqmp/__init__.py | 4 +- python/qemu/aqmp/message.py | 209 +++++++++++++++++++++++++++++++++++ 2 files changed, 212 insertions(+), 1 deletion(-) create mode 100644 python/qemu/aqmp/message.py diff --git a/python/qemu/aqmp/__init__.py b/python/qemu/aqmp/__init__.py index 88ead4c023..96fff1e5f3 100644 --- a/python/qemu/aqmp/__init__.py +++ b/python/qemu/aqmp/__init__.py @@ -22,12 +22,14 @@ # the COPYING file in the top-level directory. from .error import AQMPError +from .message import Message from .protocol import ConnectError, Runstate, StateError # The order of these fields impact the Sphinx documentation order. __all__ = ( - # Classes + # Classes, most to least important + 'Message', 'Runstate', # Exceptions, most generic to most explicit diff --git a/python/qemu/aqmp/message.py b/python/qemu/aqmp/message.py new file mode 100644 index 0000000000..f76ccc9074 --- /dev/null +++ b/python/qemu/aqmp/message.py @@ -0,0 +1,209 @@ +""" +QMP Message Format + +This module provides the `Message` class, which represents a single QMP +message sent to or from the server. +""" + +import json +from json import JSONDecodeError +from typing import ( + Dict, + Iterator, + Mapping, + MutableMapping, + Optional, + Union, +) + +from .error import ProtocolError + + +class Message(MutableMapping[str, object]): + """ + Represents a single QMP protocol message. + + QMP uses JSON objects as its basic communicative unit; so this + Python object is a :py:obj:`~collections.abc.MutableMapping`. It may + be instantiated from either another mapping (like a `dict`), or from + raw `bytes` that still need to be deserialized. + + Once instantiated, it may be treated like any other MutableMapping:: + + >>> msg = Message(b'{"hello": "world"}') + >>> assert msg['hello'] == 'world' + >>> msg['id'] = 'foobar' + >>> print(msg) + { + "hello": "world", + "id": "foobar" + } + + It can be converted to `bytes`:: + + >>> msg = Message({"hello": "world"}) + >>> print(bytes(msg)) + b'{"hello":"world","id":"foobar"}' + + Or back into a garden-variety `dict`:: + + >>> dict(msg) + {'hello': 'world'} + + + :param value: Initial value, if any. + :param eager: + When `True`, attempt to serialize or deserialize the initial value + immediately, so that conversion exceptions are raised during + the call to ``__init__()``. + """ + # pylint: disable=too-many-ancestors + + def __init__(self, + value: Union[bytes, Mapping[str, object]] = b'{}', *, + eager: bool = True): + self._data: Optional[bytes] = None + self._obj: Optional[Dict[str, object]] = None + + if isinstance(value, bytes): + self._data = value + if eager: + self._obj = self._deserialize(self._data) + else: + self._obj = dict(value) + if eager: + self._data = self._serialize(self._obj) + + # Methods necessary to implement the MutableMapping interface, see: + # https://docs.python.org/3/library/collections.abc.html#collections.abc.MutableMapping + + # We get pop, popitem, clear, update, setdefault, __contains__, + # keys, items, values, get, __eq__ and __ne__ for free. + + def __getitem__(self, key: str) -> object: + return self._object[key] + + def __setitem__(self, key: str, value: object) -> None: + self._object[key] = value + self._data = None + + def __delitem__(self, key: str) -> None: + del self._object[key] + self._data = None + + def __iter__(self) -> Iterator[str]: + return iter(self._object) + + def __len__(self) -> int: + return len(self._object) + + # Dunder methods not related to MutableMapping: + + def __repr__(self) -> str: + if self._obj is not None: + return f"Message({self._object!r})" + return f"Message({bytes(self)!r})" + + def __str__(self) -> str: + """Pretty-printed representation of this QMP message.""" + return json.dumps(self._object, indent=2) + + def __bytes__(self) -> bytes: + """bytes representing this QMP message.""" + if self._data is None: + self._data = self._serialize(self._obj or {}) + return self._data + + # Conversion Methods + + @property + def _object(self) -> Dict[str, object]: + """ + A `dict` representing this QMP message. + + Generated on-demand, if required. This property is private + because it returns an object that could be used to invalidate + the internal state of the `Message` object. + """ + if self._obj is None: + self._obj = self._deserialize(self._data or b'{}') + return self._obj + + @classmethod + def _serialize(cls, value: object) -> bytes: + """ + Serialize a JSON object as `bytes`. + + :raise ValueError: When the object cannot be serialized. + :raise TypeError: When the object cannot be serialized. + + :return: `bytes` ready to be sent over the wire. + """ + return json.dumps(value, separators=(',', ':')).encode('utf-8') + + @classmethod + def _deserialize(cls, data: bytes) -> Dict[str, object]: + """ + Deserialize JSON `bytes` into a native Python `dict`. + + :raise DeserializationError: + If JSON deserialization fails for any reason. + :raise UnexpectedTypeError: + If the data does not represent a JSON object. + + :return: A `dict` representing this QMP message. + """ + try: + obj = json.loads(data) + except JSONDecodeError as err: + emsg = "Failed to deserialize QMP message." + raise DeserializationError(emsg, data) from err + if not isinstance(obj, dict): + raise UnexpectedTypeError( + "QMP message is not a JSON object.", + obj + ) + return obj + + +class DeserializationError(ProtocolError): + """ + A QMP message was not understood as JSON. + + When this Exception is raised, ``__cause__`` will be set to the + `json.JSONDecodeError` Exception, which can be interrogated for + further details. + + :param error_message: Human-readable string describing the error. + :param raw: The raw `bytes` that prompted the failure. + """ + def __init__(self, error_message: str, raw: bytes): + super().__init__(error_message) + #: The raw `bytes` that were not understood as JSON. + self.raw: bytes = raw + + def __str__(self) -> str: + return "\n".join([ + super().__str__(), + f" raw bytes were: {str(self.raw)}", + ]) + + +class UnexpectedTypeError(ProtocolError): + """ + A QMP message was JSON, but not a JSON object. + + :param error_message: Human-readable string describing the error. + :param value: The deserialized JSON value that wasn't an object. + """ + def __init__(self, error_message: str, value: object): + super().__init__(error_message) + #: The JSON value that was expected to be an object. + self.value: object = value + + def __str__(self) -> str: + strval = json.dumps(self.value, indent=2) + return "\n".join([ + super().__str__(), + f" json value was: {strval}", + ]) -- 2.31.1