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# -*- coding: utf-8 -*-
"""
pyxs._internal
~~~~~~~~~~~~~~
A place for secret stuff, not available in the public API.
:copyright: (c) 2011 by Selectel.
:copyright: (c) 2016 by pyxs authors and contributors, see AUTHORS
for more details.
:license: LGPL, see LICENSE for more details.
"""
from __future__ import absolute_import
__all__ = ["NUL", "Event", "Op", "Packet", "next_rq_id"]
import struct
import sys
from collections import namedtuple
from .exceptions import InvalidOperation, InvalidPayload
#: NUL byte.
NUL = b"\x00"
#: Operations supported by XenStore.
Operations = Op = namedtuple("Operations", [
"DEBUG", # 0
"DIRECTORY", # 1
"READ", # 2
"GET_PERMS", # 3
"WATCH", # 4
"UNWATCH", # 5
"TRANSACTION_START", # 6
"TRANSACTION_END", # 7
"INTRODUCE", # 8
"RELEASE", # 9
"GET_DOMAIN_PATH", # 10
"WRITE", # 11
"MKDIR", # 12
"RM", # 13
"SET_PERMS", # 14
"WATCH_EVENT", # 15
"ERROR", # 16
"IS_DOMAIN_INTRODUCED", # 17
"RESUME", # 18
"SET_TARGET", # 19
"RESTRICT" # 128
])(*(list(range(20)) + [128]))
Event = namedtuple("Event", "path token")
class Packet(namedtuple("_Packet", "op rq_id tx_id size payload")):
"""A message to or from XenStore.
:param int op: an item from :data:`~pyxs._internal.Op`, representing
operation, performed by this packet.
:param bytes payload: packet payload, should be a valid ASCII-string
with characters between ``[0x20; 0x7f]``.
:param int rq_id: request id -- hopefully a **unique** identifier
for this packet, XenStore simply echoes this value
back in response.
:param int tx_id: transaction id, defaults to ``0`` , which means
no transaction is running.
.. versionchanged:: 0.4.0
``rq_id`` no longer defaults to ``0`` and should be provided
explicitly.
"""
#: ``xsd_sockmsg`` struct see ``xen/include/public/io/xs_wire.h``
#: for details.
_struct = struct.Struct(b"IIII")
def __new__(cls, op, payload, rq_id, tx_id=None):
# Checking restrictions:
# a) payload is limited to 4096 bytes.
if len(payload) > 4096:
raise InvalidPayload(payload)
# b) operation requested is present in ``xsd_sockmsg_type``.
if op not in Op:
raise InvalidOperation(op)
return super(Packet, cls).__new__(
cls, op, rq_id, tx_id or 0, len(payload), payload)
_rq_id = -1
def next_rq_id():
"""Returns the next available request id."""
# XXX we don't need a mutex because of the GIL.
global _rq_id
_rq_id += 1
_rq_id %= sys.maxsize
return _rq_id
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