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236 lines
7.2 KiB
236 lines
7.2 KiB
# -*- coding: utf-8 -*-
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from ...compat import bytes
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from ...exceptions import ReadError, SizeError
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from datetime import datetime, timedelta
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from io import BytesIO
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from struct import unpack
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__all__ = ['read_element_id', 'read_element_size', 'read_element_integer', 'read_element_uinteger',
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'read_element_float', 'read_element_string', 'read_element_unicode', 'read_element_date',
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'read_element_binary']
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def _read(stream, size):
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"""Read the `stream` for *exactly* `size` bytes and raise an exception if
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less than `size` bytes are actually read
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:param stream: file-like object from which to read
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:param int size: number of bytes to read
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:raise ReadError: when less than `size` bytes are actually read
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:return: read data from the `stream`
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:rtype: bytes
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"""
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data = stream.read(size)
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if len(data) < size:
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raise ReadError('Less than %d bytes read (%d)' % (size, len(data)))
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return data
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def read_element_id(stream):
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"""Read the Element ID
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:param stream: file-like object from which to read
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:raise ReadError: when not all the required bytes could be read
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:return: the id of the element
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:rtype: int
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"""
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char = _read(stream, 1)
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byte = ord(char)
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if byte & 0x80:
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return byte
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elif byte & 0x40:
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return unpack('>H', char + _read(stream, 1))[0]
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elif byte & 0x20:
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b, h = unpack('>BH', char + _read(stream, 2))
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return b * 2 ** 16 + h
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elif byte & 0x10:
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return unpack('>L', char + _read(stream, 3))[0]
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else:
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ValueError('Not an Element ID')
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def read_element_size(stream):
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"""Read the Element Size
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:param stream: file-like object from which to read
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:raise ReadError: when not all the required bytes could be read
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:return: the size of element's data
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:rtype: int
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"""
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char = _read(stream, 1)
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byte = ord(char)
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if byte & 0x80:
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return unpack('>B', bytes((byte ^ 0x80,)))[0]
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elif byte & 0x40:
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return unpack('>H', bytes((byte ^ 0x40,)) + _read(stream, 1))[0]
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elif byte & 0x20:
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b, h = unpack('>BH', bytes((byte ^ 0x20,)) + _read(stream, 2))
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return b * 2 ** 16 + h
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elif byte & 0x10:
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return unpack('>L', bytes((byte ^ 0x10,)) + _read(stream, 3))[0]
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elif byte & 0x08:
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b, l = unpack('>BL', bytes((byte ^ 0x08,)) + _read(stream, 4))
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return b * 2 ** 32 + l
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elif byte & 0x04:
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h, l = unpack('>HL', bytes((byte ^ 0x04,)) + _read(stream, 5))
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return h * 2 ** 32 + l
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elif byte & 0x02:
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b, h, l = unpack('>BHL', bytes((byte ^ 0x02,)) + _read(stream, 6))
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return b * 2 ** 48 + h * 2 ** 32 + l
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elif byte & 0x01:
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return unpack('>Q', bytes((byte ^ 0x01,)) + _read(stream, 7))[0]
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else:
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ValueError('Not an Element Size')
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def read_element_integer(stream, size):
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"""Read the Element Data of type :data:`INTEGER`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read integer
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:rtype: int
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"""
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if size == 1:
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return unpack('>b', _read(stream, 1))[0]
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elif size == 2:
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return unpack('>h', _read(stream, 2))[0]
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elif size == 3:
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b, h = unpack('>bH', _read(stream, 3))
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return b * 2 ** 16 + h
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elif size == 4:
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return unpack('>l', _read(stream, 4))[0]
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elif size == 5:
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b, l = unpack('>bL', _read(stream, 5))
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return b * 2 ** 32 + l
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elif size == 6:
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h, l = unpack('>hL', _read(stream, 6))
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return h * 2 ** 32 + l
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elif size == 7:
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b, h, l = unpack('>bHL', _read(stream, 7))
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return b * 2 ** 48 + h * 2 ** 32 + l
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elif size == 8:
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return unpack('>q', _read(stream, 8))[0]
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else:
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raise SizeError(size)
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def read_element_uinteger(stream, size):
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"""Read the Element Data of type :data:`UINTEGER`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read unsigned integer
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:rtype: int
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"""
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if size == 1:
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return unpack('>B', _read(stream, 1))[0]
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elif size == 2:
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return unpack('>H', _read(stream, 2))[0]
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elif size == 3:
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b, h = unpack('>BH', _read(stream, 3))
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return b * 2 ** 16 + h
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elif size == 4:
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return unpack('>L', _read(stream, 4))[0]
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elif size == 5:
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b, l = unpack('>BL', _read(stream, 5))
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return b * 2 ** 32 + l
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elif size == 6:
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h, l = unpack('>HL', _read(stream, 6))
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return h * 2 ** 32 + l
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elif size == 7:
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b, h, l = unpack('>BHL', _read(stream, 7))
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return b * 2 ** 48 + h * 2 ** 32 + l
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elif size == 8:
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return unpack('>Q', _read(stream, 8))[0]
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else:
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raise SizeError(size)
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def read_element_float(stream, size):
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"""Read the Element Data of type :data:`FLOAT`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read float
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:rtype: float
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"""
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if size == 4:
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return unpack('>f', _read(stream, 4))[0]
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elif size == 8:
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return unpack('>d', _read(stream, 8))[0]
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else:
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raise SizeError(size)
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def read_element_string(stream, size):
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"""Read the Element Data of type :data:`STRING`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read ascii-decoded string
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:rtype: unicode
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"""
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return _read(stream, size).decode('ascii')
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def read_element_unicode(stream, size):
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"""Read the Element Data of type :data:`UNICODE`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read utf-8-decoded string
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:rtype: unicode
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"""
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return _read(stream, size).decode('utf-8')
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def read_element_date(stream, size):
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"""Read the Element Data of type :data:`DATE`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: the read date
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:rtype: datetime
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"""
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if size != 8:
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raise SizeError(size)
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nanoseconds = unpack('>q', _read(stream, 8))[0]
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return datetime(2001, 1, 1, 0, 0, 0, 0, None) + timedelta(microseconds=nanoseconds // 1000)
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def read_element_binary(stream, size):
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"""Read the Element Data of type :data:`BINARY`
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:param stream: file-like object from which to read
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:param int size: size of element's data
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:raise ReadError: when not all the required bytes could be read
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:raise SizeError: if size is incorrect
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:return: raw binary data
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:rtype: bytes
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"""
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return BytesIO(stream.read(size))
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