Mercurial > hgrepos > Python > apps > py-cutils

annotate cutils/util/crc32.py @ 331:9ee84624587f

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treesum: move the handling of base64 digest output into the writers completely
author Franz Glasner <fzglas.hg@dom66.de>
date Fri, 28 Mar 2025 15:16:12 +0100
parents 48430941c18c
children
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1 # -*- coding: utf-8 -*-
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2 # :-
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3 # SPDX-FileCopyrightText: © 2025 Franz Glasner
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4 # SPDX-License-Identifier: BSD-3-Clause
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5 # :-
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6 r"""Wrap :func:`zlib.crc32` into a :mod:`hashlib` compatible interface.
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7
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8 """
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9
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10 from __future__ import print_function, absolute_import
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11
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12
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13 __all__ = ["crc32"]
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14
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15
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16 import struct
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17 import zlib
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18
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19 from . import PY2
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20
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21
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22 try:
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23 long
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24 except NameError:
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25 INT_TYPES = (int, )
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26 else:
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27 INT_TYPES = (int, long) # noqa: F821 long is undefined
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28
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29
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30 class crc32(object):
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31
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32 __slots__ = ["_crc"]
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33
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34 zlib_crc32 = zlib.crc32
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35
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36 def __init__(self, data=b""):
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37 self._crc = self.zlib_crc32(data)
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38
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39 def update(self, data):
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40 self._crc = self.zlib_crc32(data, self._crc)
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41
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42 def digest(self):
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43 return struct.pack(">I", self._get_crc_as_uint32())
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44
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45 def hexdigest(self):
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46 return "{:08X}".format(self._get_crc_as_uint32())
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47
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48 def copy(self):
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49 copied_crc = crc32()
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50 copied_crc._crc = self._crc
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51 return copied_crc
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52
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53 def __eq__(self, other):
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54 if isinstance(other, crc32):
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55 return self._crc == other._crc
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56 elif isinstance(other, INT_TYPES):
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57 try:
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58 return self._get_crc_as_uint32() == self.as_uint32(other)
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59 except OverflowError:
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60 return False
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61 else:
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62 return NotImplemented
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63
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64 def __ne__(self, other):
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65 equal = self.__eq__(other)
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66 return equal if equal is NotImplemented else not equal
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67
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68 def _get_crc_as_uint32(self):
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69 """Get the current CRC always as positive number with the same bit
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70 pattern because Python2 yields negative numbers also.
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71
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72 :return: The current CRC value as positive number on all Python
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73 versions
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74 :rtype: int
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75
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76 """
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77 if PY2:
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78 if self._crc < 0:
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79 # Return the bitpattern as unsigned 32-bit number
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80 return (~self._crc ^ 0xFFFFFFFF)
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81 else:
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82 return self._crc
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83 else:
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84 return self._crc
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85
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86 @staticmethod
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87 def as_uint32(i):
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88 if i < 0:
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89 if i < -2147483648:
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90 raise OverflowError("invalid number for a 32-bit CRC")
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91 return (~i ^ 0xFFFFFFFF)
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92 else:
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93 return i