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""" |
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The basic StarStruct element class. |
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""" |
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import re |
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import struct |
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from typing import Optional |
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from starstruct.element import register, Element |
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from starstruct.modes import Mode |
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@register |
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class ElementBase(Element): |
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""" |
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Initialize a StarStruct element object. |
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:param field: The fields passed into the constructor of the element |
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:param mode: The mode for the Element |
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:param alignment: The number of bytes to align objects with. |
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""" |
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def __init__(self, field: tuple, mode: Optional[Mode]=Mode.Native, alignment: Optional[int]=1): |
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# All of the type checks have already been performed by the class |
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# factory |
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self.name = field[0] |
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# The ref attribute is required for all elements, but the base element |
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# type does not have one |
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self.ref = None |
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self._mode = mode |
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self._alignment = alignment |
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# Validate that the format specifiers are valid struct formats, this |
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# doesn't have to be done now because the format will be checked when |
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# any struct functions are called, but it's better to inform the user of |
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# any errors earlier. |
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# The easiest way to perform this check is to create a "Struct" class |
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# instance, this will also increase the efficiency of all struct related |
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# functions called. |
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self.format = mode.value + field[1] |
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self._struct = struct.Struct(self.format) |
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@staticmethod |
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def valid(field: tuple) -> bool: |
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""" |
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Validation function to determine if a field tuple represents a valid |
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base element type. |
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The basics have already been validated by the Element factory class, |
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validate the specific struct format now. |
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Basic elements don't support numeric modifiers, since that requires a |
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list of values. |
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""" |
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return len(field) == 2 \ |
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and isinstance(field[1], str) \ |
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and re.match(r'[?nNfdP]', field[1]) |
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def validate(self, msg): |
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""" |
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Ensure that the supplied message contains the required information for |
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this element object to operate. |
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The "base" element requires no further validation. |
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""" |
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pass |
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def update(self, mode=None, alignment=None): |
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"""change the mode of the struct format""" |
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if alignment: |
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self._alignment = alignment |
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if mode: |
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self._mode = mode |
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self.format = mode.value + self.format[1:] |
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# recreate the struct with the new format |
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self._struct = struct.Struct(self.format) |
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1 |
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def pack(self, msg): |
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"""Pack the provided values into the supplied buffer.""" |
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data = self._struct.pack(msg[self.name]) |
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86
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# If the data does not meet the alignment, add some padding |
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missing_bytes = len(data) % self._alignment |
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if missing_bytes: |
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data += b'\x00' * missing_bytes |
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return data |
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1 |
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def unpack(self, msg, buf): |
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"""Unpack data from the supplied buffer using the initialized format.""" |
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ret = self._struct.unpack_from(buf, 0) |
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# Remember to remove any alignment-based padding |
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extra_bytes = self._alignment - 1 - (struct.calcsize(self.format) % |
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self._alignment) |
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unused = buf[struct.calcsize(self.format) + extra_bytes:] |
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return (ret[0], unused) |
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102
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1 |
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def make(self, msg): |
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"""Return the "transformed" value for this element""" |
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return msg[self.name] |
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sprout42 /
StarStruct
This can be caused by one of the following:
1. Missing Dependencies
This error could indicate a configuration issue of Pylint. Make sure that your libraries are available by adding the necessary commands.
2. Missing __init__.py files
This error could also result from missing
__init__.pyfiles in your module folders. Make sure that you place one file in each sub-folder.