48 lines
1.3 KiB
Python
48 lines
1.3 KiB
Python
"""
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Provides facilities for covertion from/to base91
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"""
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from math import log
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from re import findall
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def to_decimal(text):
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"""
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Takes a base91 char string and returns decimal
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"""
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if not isinstance(text, str):
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raise TypeError("expected str")
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if findall(r"[\x00-\x20\x7c-\xff]", text):
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raise ValueError("invalid character in sequence")
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decimal = 0
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length = len(text) - 1
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for i, char in enumerate(text):
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decimal += (ord(char) - 33) * (91 ** (length - i))
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return decimal if text != '' else 0
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def from_decimal(number, padding=1):
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"""
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Takes a decimal and returns base91 char string.
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With optional padding to a specific length.
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"""
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text = []
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if not isinstance(number, (int, long)) is not int or number < 0:
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raise ValueError("non-positive integer error")
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elif not isinstance(number, (int, long)) or padding < 1:
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raise ValueError("padding must be integer and >0")
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elif number > 0:
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for divisor in [91**e for e in reversed(range(int(log(number) / log(91)) + 1))]:
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quotient = number / divisor
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number = number % divisor
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text.append(chr(33 + quotient))
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# add padding if necessary
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text = ['!'] * (padding-len(text)) + text
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return "".join(text)
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