mirror of
https://github.com/DarkflameUniverse/DarkflameServer.git
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427 lines
13 KiB
Python
427 lines
13 KiB
Python
"""
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Module for sequential reading (ReadStream) and writing (WriteStream) from/to bytes.
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Also includes objects for converting datatypes from/to bytes, similar to the standard library struct module.
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"""
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# https://github.com/lcdr/bitstream/blob/master/bitstream/__init__.py
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import math
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import struct
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from abc import ABC, abstractmethod
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from typing import AnyStr, ByteString, cast, Generic, overload, SupportsBytes, Type, TypeVar
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T = TypeVar('T')
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class _Struct(Generic[T]):
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_struct: struct.Struct
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def __new__(cls, value: T) -> bytes:
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return cls._struct.pack(value)
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def __str__(self) -> str:
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return "<Struct %s>" % _Struct._struct.format
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@classmethod
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def deserialize(cls, stream: "ReadStream") -> T:
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return cast(T, cls._struct.unpack(stream.read(bytes, length=cls._struct.size))[0])
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class IntStruct(_Struct[int]):
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pass
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class UnsignedIntStruct(IntStruct):
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@classmethod
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def deserialize_compressed(cls, stream: "ReadStream") -> int:
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number_of_bytes = cls._struct.size
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current_byte = number_of_bytes - 1
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while current_byte > 0:
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if stream.read(c_bit):
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current_byte -= 1
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else:
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# Read the rest of the bytes
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read = stream.read(bytes, length=current_byte + 1) + bytes(number_of_bytes - current_byte - 1)
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return cast(int, cls._struct.unpack(read)[0])
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# All but the first bytes are 0. If the upper half of the last byte is a 0 (positive) or 16 (negative) then what we read will be a 1 and the remaining 4 bits.
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# Otherwise we read a 0 and the 8 bits
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if stream.read(c_bit):
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start = bytes([stream.read_bits(4)])
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else:
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start = stream.read(bytes, length=1)
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read = start + bytes(number_of_bytes - current_byte - 1)
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return cast(int, cls._struct.unpack(read)[0])
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class SignedIntStruct(IntStruct):
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pass
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class c_bool(_Struct[bool]):
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_struct = struct.Struct("<?")
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class c_float(_Struct[float]):
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_struct = struct.Struct("<f")
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class c_double(_Struct[float]):
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_struct = struct.Struct("<d")
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class c_int(SignedIntStruct):
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_struct = struct.Struct("<i")
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class c_uint(UnsignedIntStruct):
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_struct = struct.Struct("<I")
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class c_byte(SignedIntStruct):
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_struct = struct.Struct("<b")
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class c_ubyte(UnsignedIntStruct):
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_struct = struct.Struct("<B")
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class c_short(SignedIntStruct):
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_struct = struct.Struct("<h")
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class c_ushort(UnsignedIntStruct):
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_struct = struct.Struct("<H")
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class c_long(SignedIntStruct):
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_struct = struct.Struct("<l")
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class c_ulong(UnsignedIntStruct):
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_struct = struct.Struct("<L")
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class c_longlong(SignedIntStruct):
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_struct = struct.Struct("<q")
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class c_ulonglong(UnsignedIntStruct):
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_struct = struct.Struct("<Q")
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c_int8 = c_byte
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c_uint8 = c_ubyte
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c_int16 = c_short
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c_uint16 = c_ushort
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c_int32 = c_long
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c_uint32 = c_ulong
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c_int64 = c_longlong
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c_uint64 = c_ulonglong
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class c_bit:
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def __init__(self, boolean: bool):
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self.value = boolean
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class Serializable(ABC):
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"""By inheriting from this class you can create types which you can pass to the read/write bitstream functions."""
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@abstractmethod
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def serialize(self, stream: "WriteStream") -> None:
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"""Write this object to the bitstream."""
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pass
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@classmethod
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@abstractmethod
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def deserialize(cls, stream: "ReadStream") -> "Serializable":
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"""Create a new object from the bitstream."""
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pass
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S = TypeVar('S', bound=Serializable)
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class ReadStream:
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"""Allows simple sequential reading from bytes."""
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_data: bytes
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def __init__(self, data: bytes, unlocked: bool=False):
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self._data = data
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self._unlocked = unlocked
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self._read_offset = 0
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@property
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def read_offset(self) -> int:
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if not self._unlocked:
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raise RuntimeError("access to read offset on locked stream")
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return self._read_offset
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@read_offset.setter
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def read_offset(self, value: int) -> None:
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if not self._unlocked:
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raise RuntimeError("access to read offset on locked stream")
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self._read_offset = value
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def skip_read(self, byte_length: int) -> None:
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"""Skips reading byte_length number of bytes."""
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self._read_offset += byte_length * 8
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@overload
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def read(self, arg_type: Type[_Struct[T]]) -> T:
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pass
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@overload
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def read(self, arg_type: Type[c_bit]) -> bool:
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pass
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@overload
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def read(self, arg_type: Type[S]) -> S:
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pass
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@overload
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def read(self, arg_type: Type[bytes], length: int) -> bytes:
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pass
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@overload
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def read(self, arg_type: Type[bytes], allocated_length: int=None, length_type: Type[UnsignedIntStruct]=None) -> bytes:
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pass
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@overload
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def read(self, arg_type: Type[str], allocated_length: int=None, length_type: Type[UnsignedIntStruct]=None) -> str:
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pass
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def read(self, arg_type, length=None, allocated_length=None, length_type=None):
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"""
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Read a value of type arg_type from the bitstream.
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allocated_length is for fixed-length strings.
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length_type is for variable-length strings.
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"""
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if issubclass(arg_type, _Struct):
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return arg_type.deserialize(self)
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if issubclass(arg_type, c_bit):
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return self._read_bit()
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if issubclass(arg_type, Serializable):
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return arg_type.deserialize(self)
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if allocated_length is not None or length_type is not None:
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return self._read_str(arg_type, allocated_length, length_type)
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if issubclass(arg_type, bytes):
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return self._read_bytes(length)
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raise TypeError(arg_type)
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def _read_str(self, arg_type: Type[AnyStr], allocated_length: int=None, length_type: Type[UnsignedIntStruct]=None) -> AnyStr:
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if issubclass(arg_type, str):
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char_size = 2
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else:
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char_size = 1
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if length_type is not None:
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# Variable-length string
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length = self.read(length_type)
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value = self._read_bytes(length*char_size)
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elif allocated_length is not None:
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# Fixed-length string
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value = self._read_bytes(allocated_length*char_size)
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# find null terminator
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for i in range(len(value)):
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char = value[i*char_size:(i+1)*char_size]
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if char == bytes(char_size):
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value = value[:i*char_size]
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break
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else:
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raise RuntimeError("String doesn't have null terminator")
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else:
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raise ValueError
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if issubclass(arg_type, str):
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return value.decode("utf-16-le")
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return value
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def _read_bit(self) -> bool:
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bit = self._data[self._read_offset // 8] & 0x80 >> self._read_offset % 8 != 0
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self._read_offset += 1
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return bit
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def read_bits(self, number_of_bits: int) -> int:
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assert 0 < number_of_bits < 8
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output = (self._data[self._read_offset // 8] << self._read_offset % 8) & 0xff # First half
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if self._read_offset % 8 != 0 and number_of_bits > 8 - self._read_offset % 8: # If we have a second half, we didn't read enough bytes in the first half
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output |= self._data[self._read_offset // 8 + 1] >> 8 - self._read_offset % 8 # Second half (overlaps byte boundary)
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output >>= 8 - number_of_bits
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self._read_offset += number_of_bits
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return output
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def _read_bytes(self, length: int) -> bytes:
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if self._read_offset % 8 == 0:
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num_bytes_read = length
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else:
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num_bytes_read = length+1
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# check whether there is enough left to read
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if len(self._data) - self._read_offset//8 < num_bytes_read:
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raise EOFError("Trying to read %i bytes but only %i remain" % (num_bytes_read, len(self._data) - self._read_offset // 8))
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if self._read_offset % 8 == 0:
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output = self._data[self._read_offset // 8:self._read_offset // 8 + num_bytes_read]
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else:
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# data is shifted
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# clear the part before the struct
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firstbyte = self._data[self._read_offset // 8] & ((1 << 8 - self._read_offset % 8) - 1)
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output = firstbyte.to_bytes(1, "big") + self._data[self._read_offset // 8 + 1:self._read_offset // 8 + num_bytes_read]
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# shift back
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output = (int.from_bytes(output, "big") >> (8 - self._read_offset % 8)).to_bytes(length, "big")
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self._read_offset += length * 8
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return output
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def read_compressed(self, arg_type: Type[UnsignedIntStruct]) -> int:
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return arg_type.deserialize_compressed(self)
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def read_remaining(self) -> bytes:
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return self._read_bytes(len(self._data) - int(math.ceil(self._read_offset / 8)))
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def align_read(self) -> None:
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if self._read_offset % 8 != 0:
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self._read_offset += 8 - self._read_offset % 8
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def all_read(self) -> bool:
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# This is not accurate to the bit, just to the byte
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return math.ceil(self._read_offset / 8) == len(self._data)
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# Note: a ton of the logic here assumes that the write offset is never moved back, that is, that you never overwrite things
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# Doing so may break everything
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class WriteStream(SupportsBytes):
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"""Allows simple sequential writing to bytes."""
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_data: bytearray
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def __init__(self) -> None:
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self._data = bytearray()
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self._write_offset = 0
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self._was_cast_to_bytes = False
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def __bytes__(self) -> bytes:
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if self._was_cast_to_bytes:
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raise RuntimeError("WriteStream can only be cast to bytes once")
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self._was_cast_to_bytes = True
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return bytes(self._data)
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@overload
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def write(self, arg: ByteString) -> None:
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pass
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@overload
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def write(self, arg: _Struct) -> None:
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pass
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@overload
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def write(self, arg: c_bit) -> None:
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pass
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@overload
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def write(self, arg: Serializable) -> None:
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pass
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@overload
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def write(self, arg: AnyStr, allocated_length: int=None, length_type: Type[UnsignedIntStruct]=None) -> None:
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pass
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def write(self, arg, allocated_length=None, length_type=None):
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"""
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Write a value to the bitstream.
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allocated_length is for fixed-length strings.
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length_type is for variable-length strings.
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"""
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if isinstance(arg, c_bit):
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self._write_bit(arg.value)
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return
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if isinstance(arg, Serializable):
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arg.serialize(self)
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return
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if allocated_length is not None or length_type is not None:
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self._write_str(arg, allocated_length, length_type)
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return
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if isinstance(arg, (bytes, bytearray)):
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self._write_bytes(arg)
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return
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raise TypeError(arg)
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def _write_str(self, str_: AnyStr, allocated_length: int=None, length_type: Type[UnsignedIntStruct]=None) -> None:
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# possibly include default encoded length for non-variable-length strings (seems to be 33)
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if isinstance(str_, str):
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encoded_str = str_.encode("utf-16-le")
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else:
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encoded_str = str_
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if length_type is not None:
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# Variable-length string
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self.write(length_type(len(str_))) # note: there's also a version that uses the length of the encoded string, should that be used?
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elif allocated_length is not None:
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# Fixed-length string
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# null terminator
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if isinstance(str_, str):
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char_size = 2
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else:
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char_size = 1
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if len(str_)+1 > allocated_length:
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raise ValueError("String too long!")
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encoded_str += bytes(allocated_length*char_size-len(encoded_str))
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self._write_bytes(encoded_str)
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def _write_bit(self, bit: bool) -> None:
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self._alloc_bits(1)
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if bit: # we don't actually have to do anything if the bit is 0
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self._data[self._write_offset//8] |= 0x80 >> self._write_offset % 8
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self._write_offset += 1
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def write_bits(self, value: int, number_of_bits: int) -> None:
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assert 0 < number_of_bits < 8
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self._alloc_bits(number_of_bits)
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if number_of_bits < 8: # In the case of a partial byte, the bits are aligned from the right (bit 0) rather than the left (as in the normal internal representation)
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value = value << (8 - number_of_bits) & 0xff # Shift left to get the bits on the left, as in our internal representation
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if self._write_offset % 8 == 0:
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self._data[self._write_offset//8] = value
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else:
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self._data[self._write_offset//8] |= value >> self._write_offset % 8 # First half
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if 8 - self._write_offset % 8 < number_of_bits: # If we didn't write it all out in the first half (8 - self._write_offset % 8 is the number we wrote in the first half)
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self._data[self._write_offset//8 + 1] = (value << 8 - self._write_offset % 8) & 0xff # Second half (overlaps byte boundary)
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self._write_offset += number_of_bits
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def _write_bytes(self, byte_arg: bytes) -> None:
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if self._write_offset % 8 == 0:
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self._data[self._write_offset//8:self._write_offset//8+len(byte_arg)] = byte_arg
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else:
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# shift new input to current shift
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new = (int.from_bytes(byte_arg, "big") << (8 - self._write_offset % 8)).to_bytes(len(byte_arg)+1, "big")
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# update current byte
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self._data[self._write_offset//8] |= new[0]
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# add rest
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self._data[self._write_offset//8+1:self._write_offset//8+1+len(byte_arg)] = new[1:]
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self._write_offset += len(byte_arg)*8
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@overload
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def write_compressed(self, byte_arg: UnsignedIntStruct) -> None:
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pass
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@overload
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def write_compressed(self, byte_arg: bytes) -> None:
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pass
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def write_compressed(self, byte_arg) -> None:
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current_byte = len(byte_arg) - 1
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# Write upper bytes with a single 1
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# From high byte to low byte, if high byte is 0 then write 1. Otherwise write 0 and the remaining bytes
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while current_byte > 0:
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is_zero = byte_arg[current_byte] == 0
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self._write_bit(is_zero)
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if not is_zero:
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# Write the remainder of the data
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self._write_bytes(byte_arg[:current_byte + 1])
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return
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current_byte -= 1
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# If the upper half of the last byte is 0 then write 1 and the remaining 4 bits. Otherwise write 0 and the 8 bits.
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is_zero = byte_arg[0] & 0xF0 == 0x00
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self._write_bit(is_zero)
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if is_zero:
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self.write_bits(byte_arg[0], 4)
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else:
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self._write_bytes(byte_arg[:1])
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def align_write(self) -> None:
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"""Align the write offset to the byte boundary."""
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if self._write_offset % 8 != 0:
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self._alloc_bits(8 - self._write_offset % 8)
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self._write_offset += 8 - self._write_offset % 8
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def _alloc_bits(self, number_of_bits: int) -> None:
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bytes_to_allocate: int = math.ceil((self._write_offset + number_of_bits) / 8) - len(self._data)
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if bytes_to_allocate > 0:
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self._data += bytes(bytes_to_allocate) |