Telethon/telethon/extensions/binaryreader.py

197 lines
5.9 KiB
Python

"""
This module contains the BinaryReader utility class.
"""
import os
from datetime import datetime, timezone, timedelta
from io import BufferedReader, BytesIO
from struct import unpack
import time
from ..errors import TypeNotFoundError
from ..tl.alltlobjects import tlobjects
from ..tl.core import core_objects
_EPOCH_NAIVE = datetime(*time.gmtime(0)[:6])
_EPOCH = _EPOCH_NAIVE.replace(tzinfo=timezone.utc)
class BinaryReader:
"""
Small utility class to read binary data.
Also creates a "Memory Stream" if necessary
"""
def __init__(self, data=None, stream=None):
if data:
self.stream = BytesIO(data)
elif stream:
self.stream = stream
else:
raise ValueError('Either bytes or a stream must be provided')
self.reader = BufferedReader(self.stream)
self._last = None # Should come in handy to spot -404 errors
# region Reading
# "All numbers are written as little endian."
# https://core.telegram.org/mtproto
def read_byte(self):
"""Reads a single byte value."""
return self.read(1)[0]
def read_int(self, signed=True):
"""Reads an integer (4 bytes) value."""
return int.from_bytes(self.read(4), byteorder='little', signed=signed)
def read_long(self, signed=True):
"""Reads a long integer (8 bytes) value."""
return int.from_bytes(self.read(8), byteorder='little', signed=signed)
def read_float(self):
"""Reads a real floating point (4 bytes) value."""
return unpack('<f', self.read(4))[0]
def read_double(self):
"""Reads a real floating point (8 bytes) value."""
return unpack('<d', self.read(8))[0]
def read_large_int(self, bits, signed=True):
"""Reads a n-bits long integer value."""
return int.from_bytes(
self.read(bits // 8), byteorder='little', signed=signed)
def read(self, length=None):
"""Read the given amount of bytes."""
if length is None:
return self.reader.read()
result = self.reader.read(length)
if len(result) != length:
raise BufferError(
'No more data left to read (need {}, got {}: {}); last read {}'
.format(length, len(result), repr(result), repr(self._last))
)
self._last = result
return result
def get_bytes(self):
"""Gets the byte array representing the current buffer as a whole."""
return self.stream.getvalue()
# endregion
# region Telegram custom reading
def tgread_bytes(self):
"""
Reads a Telegram-encoded byte array, without the need of
specifying its length.
"""
first_byte = self.read_byte()
if first_byte == 254:
length = self.read_byte() | (self.read_byte() << 8) | (
self.read_byte() << 16)
padding = length % 4
else:
length = first_byte
padding = (length + 1) % 4
data = self.read(length)
if padding > 0:
padding = 4 - padding
self.read(padding)
return data
def tgread_string(self):
"""Reads a Telegram-encoded string."""
return str(self.tgread_bytes(), encoding='utf-8', errors='replace')
def tgread_bool(self):
"""Reads a Telegram boolean value."""
value = self.read_int(signed=False)
if value == 0x997275b5: # boolTrue
return True
elif value == 0xbc799737: # boolFalse
return False
else:
raise RuntimeError('Invalid boolean code {}'.format(hex(value)))
def tgread_date(self):
"""Reads and converts Unix time (used by Telegram)
into a Python datetime object.
"""
value = self.read_int()
return _EPOCH + timedelta(seconds=value)
def tgread_object(self):
"""Reads a Telegram object."""
constructor_id = self.read_int(signed=False)
clazz = tlobjects.get(constructor_id, None)
if clazz is None:
# The class was None, but there's still a
# chance of it being a manually parsed value like bool!
value = constructor_id
if value == 0x997275b5: # boolTrue
return True
elif value == 0xbc799737: # boolFalse
return False
elif value == 0x1cb5c415: # Vector
return [self.tgread_object() for _ in range(self.read_int())]
clazz = core_objects.get(constructor_id, None)
if clazz is None:
# If there was still no luck, give up
self.seek(-4) # Go back
pos = self.tell_position()
error = TypeNotFoundError(constructor_id, self.read())
self.set_position(pos)
raise error
return clazz.from_reader(self)
def tgread_vector(self):
"""Reads a vector (a list) of Telegram objects."""
if 0x1cb5c415 != self.read_int(signed=False):
raise RuntimeError('Invalid constructor code, vector was expected')
count = self.read_int()
return [self.tgread_object() for _ in range(count)]
# endregion
def close(self):
"""Closes the reader, freeing the BytesIO stream."""
self.reader.close()
# region Position related
def tell_position(self):
"""Tells the current position on the stream."""
return self.reader.tell()
def set_position(self, position):
"""Sets the current position on the stream."""
self.reader.seek(position)
def seek(self, offset):
"""
Seeks the stream position given an offset from the current position.
The offset may be negative.
"""
self.reader.seek(offset, os.SEEK_CUR)
# endregion
# region with block
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.close()
# endregion