feat: improve unmarshaller performance (#43)
This commit is contained in:
J. Nick Koston
GitHub
parent
cb34059849
commit
c4b4a038f8
@ -42,6 +42,11 @@ DBUS_TO_CTYPE = {
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"h": ("I", 4), # uint32
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}
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UINT32_UNPACK_BY_ENDIAN = {
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LITTLE_ENDIAN: Struct("<I").unpack_from,
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BIG_ENDIAN: Struct(">I").unpack_from,
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}
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HEADER_SIGNATURE_SIZE = 16
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HEADER_ARRAY_OF_STRUCT_SIGNATURE_POSITION = 12
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@ -53,15 +58,44 @@ HEADER_ERROR_NAME = HeaderField.ERROR_NAME.name
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HEADER_REPLY_SERIAL = HeaderField.REPLY_SERIAL.name
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HEADER_SENDER = HeaderField.SENDER.name
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READER_TYPE = Dict[
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str,
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Tuple[
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Optional[Callable[["Unmarshaller", SignatureType], Any]],
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Optional[str],
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Optional[int],
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Optional[Struct],
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],
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]
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READER_TYPE = Callable[["Unmarshaller", SignatureType], Any]
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def cast_parser_factory(ctype: str, size: int) -> READER_TYPE:
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"""Build a parser that casts the bytes to the given ctype."""
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def _cast_parser(self: "Unmarshaller", signature: SignatureType) -> Any:
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self.pos += size + (-self.pos & (size - 1)) # align
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return self.view[self.pos - size : self.pos].cast(ctype)[0]
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return _cast_parser
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def unpack_parser_factory(unpack_from: Callable, size: int) -> READER_TYPE:
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"""Build a parser that unpacks the bytes using the given unpack_from function."""
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def _unpack_from_parser(self: "Unmarshaller", signature: SignatureType) -> Any:
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self.pos += size + (-self.pos & (size - 1)) # align
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return unpack_from(self.view, self.pos - size)[0]
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return _unpack_from_parser
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def build_simple_parsers(
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endian: int, can_cast: bool
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) -> Dict[str, Callable[["Unmarshaller", SignatureType], Any]]:
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"""Build a dict of parsers for simple types."""
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parsers: Dict[str, Callable[["Unmarshaller", SignatureType], Any]] = {}
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for dbus_type, ctype_size in DBUS_TO_CTYPE.items():
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ctype, size = ctype_size
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size = ctype_size[1]
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if can_cast:
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parsers[dbus_type] = cast_parser_factory(ctype, size)
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else:
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parsers[dbus_type] = unpack_parser_factory(
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Struct(f"{UNPACK_SYMBOL[endian]}{ctype}").unpack_from, size
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)
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return parsers
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class MarshallerStreamEndError(Exception):
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@ -186,7 +220,7 @@ class Unmarshaller:
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raise MarshallerStreamEndError()
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def read_boolean(self, _=None):
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return bool(self.read_argument(UINT32_SIGNATURE))
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return bool(self.readers[UINT32_SIGNATURE.token](self, UINT32_SIGNATURE))
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def read_string_cast(self, _=None):
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"""Read a string using cast."""
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@ -216,17 +250,22 @@ class Unmarshaller:
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def read_variant(self, _=None):
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tree = SignatureTree._get(self.read_signature())
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# verify in Variant is only useful on construction not unmarshalling
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return Variant(tree, self.read_argument(tree.types[0]), verify=False)
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return Variant(
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tree, self.readers[tree.types[0].token](self, tree.types[0]), verify=False
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)
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def read_struct(self, type_: SignatureType):
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self.pos += -self.pos & 7 # align 8
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return [self.read_argument(child_type) for child_type in type_.children]
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return [
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self.readers[child_type.token](self, child_type)
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for child_type in type_.children
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]
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def read_dict_entry(self, type_: SignatureType):
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self.pos += -self.pos & 7 # align 8
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return self.read_argument(type_.children[0]), self.read_argument(
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type_.children[1]
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)
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return self.readers[type_.children[0].token](
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self, type_.children[0]
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), self.readers[type_.children[1].token](self, type_.children[1])
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def read_array(self, type_: SignatureType):
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self.pos += -self.pos & 3 # align 4 for the array
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@ -255,25 +294,19 @@ class Unmarshaller:
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result_dict = {}
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while self.pos - beginning_pos < array_length:
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self.pos += -self.pos & 7 # align 8
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key = self.read_argument(child_type.children[0])
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result_dict[key] = self.read_argument(child_type.children[1])
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key = self.readers[child_type.children[0].token](
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self, child_type.children[0]
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)
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result_dict[key] = self.readers[child_type.children[1].token](
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self, child_type.children[1]
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)
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return result_dict
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result_list = []
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while self.pos - beginning_pos < array_length:
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result_list.append(self.read_argument(child_type))
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result_list.append(self.readers[child_type.token](self, child_type))
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return result_list
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def read_argument(self, type_: SignatureType) -> Any:
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"""Dispatch to an argument reader or cast/unpack a C type."""
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reader, ctype, size, struct = self.readers[type_.token]
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if reader: # complex type
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return reader(self, type_)
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self.pos += size + (-self.pos & (size - 1)) # align
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if struct: # struct only set if we cannot cast
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return struct(self.view, self.pos - size)[0]
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return self.view[self.pos - size : self.pos].cast(ctype)[0]
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def header_fields(self, header_length):
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"""Header fields are always a(yv)."""
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beginning_pos = self.pos
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@ -288,7 +321,9 @@ class Unmarshaller:
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o = self.pos + 1
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self.pos += signature_len + 2 # one for the byte, one for the '\0'
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tree = SignatureTree._get(self.buf[o : o + signature_len].decode())
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headers[HEADER_NAME_MAP[field_0]] = self.read_argument(tree.types[0])
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headers[HEADER_NAME_MAP[field_0]] = self.readers[tree.types[0].token](
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self, tree.types[0]
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)
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return headers
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def _read_header(self):
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@ -323,7 +358,7 @@ class Unmarshaller:
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)
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self.readers = self._readers_by_type[(endian, can_cast)]
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if not can_cast:
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self._uint32_unpack = self.readers[UINT32_DBUS_TYPE][3]
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self._uint32_unpack = UINT32_UNPACK_BY_ENDIAN[endian]
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def _read_body(self):
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"""Read the body of the message."""
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@ -345,7 +380,9 @@ class Unmarshaller:
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sender=header_fields.get(HEADER_SENDER),
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unix_fds=self.unix_fds,
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signature=tree.signature,
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body=[self.read_argument(t) for t in tree.types] if self.body_len else [],
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body=[self.readers[t.token](self, t) for t in tree.types]
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if self.body_len
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else [],
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serial=self.serial,
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# The D-Bus implementation already validates the message,
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# so we don't need to do it again.
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@ -368,46 +405,33 @@ class Unmarshaller:
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return self.message
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_complex_parsers_unpack: Dict[
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str, Tuple[Callable[["Unmarshaller", SignatureType], Any], None, None, None]
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str, Callable[["Unmarshaller", SignatureType], Any]
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] = {
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"b": (read_boolean, None, None, None),
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"o": (read_string_unpack, None, None, None),
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"s": (read_string_unpack, None, None, None),
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"g": (read_signature, None, None, None),
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"a": (read_array, None, None, None),
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"(": (read_struct, None, None, None),
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"{": (read_dict_entry, None, None, None),
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"v": (read_variant, None, None, None),
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"b": read_boolean,
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"o": read_string_unpack,
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"s": read_string_unpack,
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"g": read_signature,
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"a": read_array,
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"(": read_struct,
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"{": read_dict_entry,
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"v": read_variant,
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}
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_complex_parsers_cast: Dict[
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str, Tuple[Callable[["Unmarshaller", SignatureType], Any], None, None, None]
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] = {
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"b": (read_boolean, None, None, None),
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"o": (read_string_cast, None, None, None),
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"s": (read_string_cast, None, None, None),
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"g": (read_signature, None, None, None),
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"a": (read_array, None, None, None),
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"(": (read_struct, None, None, None),
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"{": (read_dict_entry, None, None, None),
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"v": (read_variant, None, None, None),
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_complex_parsers_cast: Dict[str, Callable[["Unmarshaller", SignatureType], Any]] = {
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"b": read_boolean,
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"o": read_string_cast,
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"s": read_string_cast,
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"g": read_signature,
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"a": read_array,
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"(": read_struct,
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"{": read_dict_entry,
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"v": read_variant,
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}
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_ctype_by_endian: Dict[
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Tuple[int, bool], Dict[str, Tuple[None, str, int, Callable]]
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] = {
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endian_can_cast: {
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dbus_type: (
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None,
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*ctype_size,
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None
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if endian_can_cast[1]
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else Struct(
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f"{UNPACK_SYMBOL[endian_can_cast[0]]}{ctype_size[0]}"
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).unpack_from,
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)
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for dbus_type, ctype_size in DBUS_TO_CTYPE.items()
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}
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endian_can_cast: build_simple_parsers(*endian_can_cast)
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for endian_can_cast in [
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(LITTLE_ENDIAN, True),
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(LITTLE_ENDIAN, False),
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@ -32,6 +32,7 @@ class SignatureType:
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"""
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_tokens = "ybnqiuxtdsogavh({"
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__slots__ = ("token", "children", "_signature")
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def __init__(self, token: str) -> None:
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self.token = token
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