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https://github.com/PiBrewing/craftbeerpi4.git
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137 lines
4.2 KiB
Python
137 lines
4.2 KiB
Python
""" Concise UUID generation. """
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import binascii
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import math
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import os
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import uuid as _uu
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def int_to_string(number, alphabet, padding=None):
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"""
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Convert a number to a string, using the given alphabet.
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The output has the most significant digit first.
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"""
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output = ""
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alpha_len = len(alphabet)
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while number:
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number, digit = divmod(number, alpha_len)
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output += alphabet[digit]
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if padding:
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remainder = max(padding - len(output), 0)
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output = output + alphabet[0] * remainder
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return output[::-1]
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def string_to_int(string, alphabet):
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"""
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Convert a string to a number, using the given alphabet.
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The input is assumed to have the most significant digit first.
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"""
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number = 0
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alpha_len = len(alphabet)
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for char in string:
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number = number * alpha_len + alphabet.index(char)
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return number
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class ShortUUID(object):
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def __init__(self, alphabet=None):
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if alphabet is None:
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alphabet = list("23456789ABCDEFGHJKLMNPQRSTUVWXYZ" "abcdefghijkmnopqrstuvwxyz")
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self.set_alphabet(alphabet)
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@property
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def _length(self):
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"""
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Return the necessary length to fit the entire UUID given
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the current alphabet.
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"""
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return int(math.ceil(math.log(2 ** 128, self._alpha_len)))
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def encode(self, uuid, pad_length=None):
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"""
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Encode a UUID into a string (LSB first) according to the alphabet
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If leftmost (MSB) bits are 0, the string might be shorter.
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"""
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if pad_length is None:
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pad_length = self._length
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return int_to_string(uuid.int, self._alphabet, padding=pad_length)
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def decode(self, string, legacy=False):
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"""
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Decode a string according to the current alphabet into a UUID
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Raises ValueError when encountering illegal characters
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or a too-long string.
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If string too short, fills leftmost (MSB) bits with 0.
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Pass `legacy=True` if your UUID was encoded with a ShortUUID version
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prior to 1.0.0.
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"""
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if legacy:
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string = string[::-1]
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return _uu.UUID(int=string_to_int(string, self._alphabet))
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def uuid(self, name=None, pad_length=None):
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"""
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Generate and return a UUID.
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If the name parameter is provided, set the namespace to the provided
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name and generate a UUID.
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"""
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if pad_length is None:
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pad_length = self._length
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# If no name is given, generate a random UUID.
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if name is None:
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u = _uu.uuid4()
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elif name.lower().startswith(("http://", "https://")):
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u = _uu.uuid5(_uu.NAMESPACE_URL, name)
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else:
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u = _uu.uuid5(_uu.NAMESPACE_DNS, name)
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return self.encode(u, pad_length)
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def random(self, length=None):
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"""
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Generate and return a cryptographically-secure short random string
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of the specified length.
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"""
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if length is None:
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length = self._length
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random_num = int(binascii.b2a_hex(os.urandom(length)), 16)
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return int_to_string(random_num, self._alphabet, padding=length)[:length]
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def get_alphabet(self):
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"""Return the current alphabet used for new UUIDs."""
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return "".join(self._alphabet)
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def set_alphabet(self, alphabet):
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"""Set the alphabet to be used for new UUIDs."""
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# Turn the alphabet into a set and sort it to prevent duplicates
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# and ensure reproducibility.
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new_alphabet = list(sorted(set(alphabet)))
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if len(new_alphabet) > 1:
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self._alphabet = new_alphabet
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self._alpha_len = len(self._alphabet)
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else:
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raise ValueError("Alphabet with more than " "one unique symbols required.")
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def encoded_length(self, num_bytes=16):
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"""
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Returns the string length of the shortened UUID.
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"""
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factor = math.log(256) / math.log(self._alpha_len)
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return int(math.ceil(factor * num_bytes))
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# For backwards compatibility
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_global_instance = ShortUUID()
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encode = _global_instance.encode
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decode = _global_instance.decode
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uuid = _global_instance.uuid
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random = _global_instance.random
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get_alphabet = _global_instance.get_alphabet
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set_alphabet = _global_instance.set_alphabet
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