1
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""" |
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The constant element class for StarStruct |
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To be used in the following way: |
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6
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ExampleMessage = Message('constant_message', [ |
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('regular', 'B'), # Two regular messages |
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('fill_in_later', 'H'), |
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('ending_sequence', 'II', (0xAA, 0xBB)), # An ending sequence to a message |
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# that's always the same |
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]) |
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:todo: Not sure if alignment is working correctly here, or if it needs to do anything |
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""" |
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import struct |
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from typing import Optional, Tuple |
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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 ElementConstant(Element): |
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def __init__(self, field, mode=Mode.Native, alignment=1): |
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self.name = field[0] |
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self.format = field[1] |
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self.values = field[2] |
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self._mode = mode |
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self._alignment = alignment |
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@property |
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def _struct(self): |
36
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return struct.Struct(self._mode.value + self.format) |
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38
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@property |
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def _packed(self): |
40
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return self._struct.pack(*self.values) |
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42
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@staticmethod |
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def valid(field: list) -> bool: |
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""" |
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Validate whether this field could supply this element with the corect values |
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""" |
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return len(field) == 3 \ |
48
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and isinstance(field[0], str) \ |
49
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and isinstance(field[1], str) \ |
50
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and struct.calcsize(field[1]) \ |
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and isinstance(field[2], tuple) |
52
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53
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def validate(self, msg): |
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""" |
55
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Ensure that the supplied message contains the required information for |
56
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this element object to operate. |
57
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58
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Constants will alawys be valid |
59
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""" |
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return True |
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62
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def update(self, mode: Optional[Tuple]=None, alignment: Optional[int]=1) -> None: |
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"""change the mode of the struct format""" |
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if mode: |
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self._mode = mode |
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67
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if alignment: |
68
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self._alignment = alignment |
69
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70
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def pack(self, msg: dict) -> bytes: |
71
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""" |
72
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Pack the provided values into the supplied buffer. |
73
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74
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:param msg: The message specifying the values to pack |
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""" |
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return self._packed |
77
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78
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def unpack(self, msg: dict, buf: bytes) -> Tuple[bytes, bytes]: |
79
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"""Unpack data from the supplied buffer using the initialized format.""" |
80
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return (self._struct.unpack_from(buf), buf[self._struct.size:]) |
81
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82
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def make(self, msg: dict): |
83
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""" |
84
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Return the expected "made" value |
85
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86
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:param msg: The values to make |
87
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""" |
88
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return self.values |
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__init__.py
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