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Defer decoding known answers until needed #983

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Merged
bdraco merged 2 commits into from
Sep 16, 2021
Merged

Defer decoding known answers until needed #983

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43d42e8
Defer decoding known answers until needed
bdraco Sep 16, 2021
eed76d9
Dry
bdraco Sep 16, 2021
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2 changes: 1 addition & 1 deletion zeroconf/_handlers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -348,7 +348,7 @@ def async_response( # pylint: disable=unused-argument
threadsafe.
"""
known_answers = DNSRRSet(
itertools.chain(*(msg.answers for msg in msgs if not _message_is_probe(msg)))
itertools.chain.from_iterable(msg.answers for msg in msgs if not _message_is_probe(msg))
)
query_res = _QueryResponse(self.cache, msgs)

Expand Down
33 changes: 25 additions & 8 deletions zeroconf/_protocol.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@

import enum
import struct
from typing import Any, Dict, List, Optional, Sequence, Set, TYPE_CHECKING, Tuple, Union, cast
from typing import Any, Callable, Dict, List, Optional, Sequence, Set, TYPE_CHECKING, Tuple, Union, cast


from ._dns import DNSAddress, DNSHinfo, DNSNsec, DNSPointer, DNSQuestion, DNSRecord, DNSService, DNSText
Expand Down Expand Up @@ -96,23 +96,39 @@ def __init__(self, data: bytes, scope_id: Optional[int] = None, now: Optional[fl
self.name_cache: Dict[int, List[str]] = {}
self.seen_pointers: Set[int] = set()
self.questions: List[DNSQuestion] = []
self.answers: List[DNSRecord] = []
self._answers: List[DNSRecord] = []
self.id = 0
self.num_questions = 0
self.num_answers = 0
self.num_authorities = 0
self.num_additionals = 0
self.valid = False
self._read_others = False
self.now = now or current_time_millis()
self.scope_id = scope_id
self._parse_data(self._initial_parse)

try:
self.read_header()
self.read_questions()
def _initial_parse(self) -> None:
"""Parse the data needed to initalize the packet object."""
self.read_header()
self.read_questions()
if not self.num_questions:
self.read_others()
self.valid = True
self.valid = True

def _parse_data(self, parser_call: Callable) -> None:
"""Parse part of the packet and catch exceptions."""
try:
parser_call()
except DECODE_EXCEPTIONS:
self.log_exception_warning('Choked at offset %d while unpacking %r', self.offset, data)
self.log_exception_warning('Choked at offset %d while unpacking %r', self.offset, self.data)

@property
def answers(self) -> List[DNSRecord]:
"""Answers in the packet."""
if not self._read_others:
self._parse_data(self.read_others)
return self._answers

def __repr__(self) -> str:
return '<DNSIncoming:{%s}>' % ', '.join(
Expand Down Expand Up @@ -170,6 +186,7 @@ def read_unsigned_short(self) -> int:
def read_others(self) -> None:
"""Reads the answers, authorities and additionals section of the
packet"""
self._read_others = True
n = self.num_answers + self.num_authorities + self.num_additionals
for _ in range(n):
domain = self.read_name()
Expand All @@ -192,7 +209,7 @@ def read_others(self) -> None:
exc_info=True,
)
if rec is not None:
self.answers.append(rec)
self._answers.append(rec)

def read_record(self, domain: str, type_: int, class_: int, ttl: int, length: int) -> Optional[DNSRecord]:
"""Read known records types and skip unknown ones."""
Expand Down