mirror of https://github.com/morpheus65535/bazarr
90 lines
2.8 KiB
Python
90 lines
2.8 KiB
Python
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
|
|
|
|
import contextlib
|
|
import struct
|
|
from typing import Iterator, Optional, Tuple
|
|
|
|
import dns.exception
|
|
import dns.name
|
|
|
|
|
|
class Parser:
|
|
def __init__(self, wire: bytes, current: int = 0):
|
|
self.wire = wire
|
|
self.current = 0
|
|
self.end = len(self.wire)
|
|
if current:
|
|
self.seek(current)
|
|
self.furthest = current
|
|
|
|
def remaining(self) -> int:
|
|
return self.end - self.current
|
|
|
|
def get_bytes(self, size: int) -> bytes:
|
|
assert size >= 0
|
|
if size > self.remaining():
|
|
raise dns.exception.FormError
|
|
output = self.wire[self.current : self.current + size]
|
|
self.current += size
|
|
self.furthest = max(self.furthest, self.current)
|
|
return output
|
|
|
|
def get_counted_bytes(self, length_size: int = 1) -> bytes:
|
|
length = int.from_bytes(self.get_bytes(length_size), "big")
|
|
return self.get_bytes(length)
|
|
|
|
def get_remaining(self) -> bytes:
|
|
return self.get_bytes(self.remaining())
|
|
|
|
def get_uint8(self) -> int:
|
|
return struct.unpack("!B", self.get_bytes(1))[0]
|
|
|
|
def get_uint16(self) -> int:
|
|
return struct.unpack("!H", self.get_bytes(2))[0]
|
|
|
|
def get_uint32(self) -> int:
|
|
return struct.unpack("!I", self.get_bytes(4))[0]
|
|
|
|
def get_uint48(self) -> int:
|
|
return int.from_bytes(self.get_bytes(6), "big")
|
|
|
|
def get_struct(self, format: str) -> Tuple:
|
|
return struct.unpack(format, self.get_bytes(struct.calcsize(format)))
|
|
|
|
def get_name(self, origin: Optional["dns.name.Name"] = None) -> "dns.name.Name":
|
|
name = dns.name.from_wire_parser(self)
|
|
if origin:
|
|
name = name.relativize(origin)
|
|
return name
|
|
|
|
def seek(self, where: int) -> None:
|
|
# Note that seeking to the end is OK! (If you try to read
|
|
# after such a seek, you'll get an exception as expected.)
|
|
if where < 0 or where > self.end:
|
|
raise dns.exception.FormError
|
|
self.current = where
|
|
|
|
@contextlib.contextmanager
|
|
def restrict_to(self, size: int) -> Iterator:
|
|
assert size >= 0
|
|
if size > self.remaining():
|
|
raise dns.exception.FormError
|
|
saved_end = self.end
|
|
try:
|
|
self.end = self.current + size
|
|
yield
|
|
# We make this check here and not in the finally as we
|
|
# don't want to raise if we're already raising for some
|
|
# other reason.
|
|
if self.current != self.end:
|
|
raise dns.exception.FormError
|
|
finally:
|
|
self.end = saved_end
|
|
|
|
@contextlib.contextmanager
|
|
def restore_furthest(self) -> Iterator:
|
|
try:
|
|
yield None
|
|
finally:
|
|
self.current = self.furthest
|