def _read_unpack(self,
size=1,
*,
signed=False,
lilendian=False,
quiet=False):
"""Read bytes and unpack for integers.
Positional arguments:
* size -- int, buffer size (default is 1)
Keyword arguments:
* signed -- bool, signed flag (default is False)
<keyword> True / False
* lilendian -- bool, little-endian flag (default is False)
<keyword> True / False
* quiet -- bool, quiet (no exception) flag (default is False)
<keyword> True / False
Returns:
* int -- unpacked data upon success
"""
endian = '<' if lilendian else '>'
if size == 8: # unpack to 8-byte integer (long long)
kind = 'q' if signed else 'Q'
elif size == 4: # unpack to 4-byte integer (int / long)
kind = 'i' if signed else 'I'
elif size == 2: # unpack to 2-byte integer (short)
kind = 'h' if signed else 'H'
elif size == 1: # unpack to 1-byte integer (char)
kind = 'b' if signed else 'B'
else: # do not unpack
kind = None
if kind is None:
mem = self._file.read(size)
end = 'little' if lilendian else 'big'
buf = int.from_bytes(mem, end, signed=signed)
else:
try:
fmt = f'{endian}{kind}'
mem = self._file.read(size)
buf = struct.unpack(fmt, mem)[0]
except struct.error:
if quiet:
return None
else:
raise StructError(
f'{self.__class__.__name__}: unpack failed') from None
return buf
def _read_unpack(self,
size=1,
*,
signed=False,
lilendian=False,
quiet=False):
"""Read bytes and unpack for integers.
Arguments:
size (int): buffer size
Keyword Arguments:
signed (bool): signed flag
lilendian (bool): little-endian flag
quiet (bool): quiet (no exception) flag
Returns:
Optional[int]: unpacked data upon success
Raises:
StructError: If unpack (:func:`struct.pack`) failed, and :exc:`struct.error` raised.
"""
endian = '<' if lilendian else '>'
if size == 8: # unpack to 8-byte integer (long long)
kind = 'q' if signed else 'Q'
elif size == 4: # unpack to 4-byte integer (int / long)
kind = 'i' if signed else 'I'
elif size == 2: # unpack to 2-byte integer (short)
kind = 'h' if signed else 'H'
elif size == 1: # unpack to 1-byte integer (char)
kind = 'b' if signed else 'B'
else: # do not unpack
kind = None
if kind is None:
mem = self._file.read(size)
end = 'little' if lilendian else 'big'
buf = int.from_bytes(mem, end, signed=signed)
else:
try:
fmt = f'{endian}{kind}'
mem = self._file.read(size)
buf = struct.unpack(fmt, mem)[0]
except struct.error:
if quiet:
return None
raise StructError(f'{self.__class__.__name__}: unpack failed')
return buf
def _make_pack(cls, integer, *, size=1, signed=False, lilendian=False):
"""Pack integers to bytes.
Arguments:
integer (int) integer to be packed
Keyword arguments:
size (int): buffer size
signed (bool): signed flag
lilendian (bool): little-endian flag
Returns:
bytes: Packed data upon success.
Raises:
StructError: If failed to pack the integer.
"""
endian = '<' if lilendian else '>'
if size == 8: # unpack to 8-byte integer (long long)
kind = 'q' if signed else 'Q'
elif size == 4: # unpack to 4-byte integer (int / long)
kind = 'i' if signed else 'I'
elif size == 2: # unpack to 2-byte integer (short)
kind = 'h' if signed else 'H'
elif size == 1: # unpack to 1-byte integer (char)
kind = 'b' if signed else 'B'
else: # do not unpack
kind = None
if kind is None:
end = 'little' if lilendian else 'big'
buf = integer.to_bytes(size, end, signed=signed)
else:
try:
fmt = f'{endian}{kind}'
buf = struct.pack(fmt, integer)
except struct.error:
raise StructError(f'{cls.__name__}: pack failed') from None
return buf
def pack(cls, integer, *, size=1, signed=False, lilendian=False):
"""Pack integers to bytes.
Positional arguments:
* integer -- int, integer to be packed
Keyword arguments:
* size -- int, buffer size (default is 1)
* signed -- bool, signed flag (default is False)
<keyword> True / False
* lilendian -- bool, little-endian flag (default is False)
<keyword> True / False
Returns:
* bytes -- packed data upon success
"""
endian = '<' if lilendian else '>'
if size == 8: # unpack to 8-byte integer (long long)
kind = 'q' if signed else 'Q'
elif size == 4: # unpack to 4-byte integer (int / long)
kind = 'i' if signed else 'I'
elif size == 2: # unpack to 2-byte integer (short)
kind = 'h' if signed else 'H'
elif size == 1: # unpack to 1-byte integer (char)
kind = 'b' if signed else 'B'
else: # do not unpack
kind = None
if kind is None:
end = 'little' if lilendian else 'big'
buf = integer.to_bytes(size, end, signed=signed)
else:
try:
fmt = f'{endian}{kind}'
buf = struct.pack(fmt, integer)
except struct.error:
raise StructError(f'{cls.__name__}: pack failed') from None
return buf