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https://github.com/Sneed-Group/Poodletooth-iLand
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119 lines
4 KiB
Python
119 lines
4 KiB
Python
# -*- coding: ascii -*-
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#
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# Util/_number_new.py : utility functions
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#
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# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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## NOTE: Do not import this module directly. Import these functions from Crypto.Util.number.
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__revision__ = "$Id$"
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__all__ = ['ceil_shift', 'ceil_div', 'floor_div', 'exact_log2', 'exact_div']
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import sys
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if sys.version_info[0] == 2 and sys.version_info[1] == 1:
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from Crypto.Util.py21compat import *
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def ceil_shift(n, b):
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"""Return ceil(n / 2**b) without performing any floating-point or division operations.
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This is done by right-shifting n by b bits and incrementing the result by 1
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if any '1' bits were shifted out.
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"""
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if not isinstance(n, (int, long)) or not isinstance(b, (int, long)):
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raise TypeError("unsupported operand type(s): %r and %r" % (type(n).__name__, type(b).__name__))
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assert n >= 0 and b >= 0 # I haven't tested or even thought about negative values
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mask = (1L << b) - 1
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if n & mask:
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return (n >> b) + 1
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else:
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return n >> b
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def ceil_div(a, b):
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"""Return ceil(a / b) without performing any floating-point operations."""
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if not isinstance(a, (int, long)) or not isinstance(b, (int, long)):
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raise TypeError("unsupported operand type(s): %r and %r" % (type(a).__name__, type(b).__name__))
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(q, r) = divmod(a, b)
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if r:
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return q + 1
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else:
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return q
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def floor_div(a, b):
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if not isinstance(a, (int, long)) or not isinstance(b, (int, long)):
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raise TypeError("unsupported operand type(s): %r and %r" % (type(a).__name__, type(b).__name__))
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(q, r) = divmod(a, b)
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return q
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def exact_log2(num):
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"""Find and return an integer i >= 0 such that num == 2**i.
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If no such integer exists, this function raises ValueError.
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"""
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if not isinstance(num, (int, long)):
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raise TypeError("unsupported operand type: %r" % (type(num).__name__,))
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n = long(num)
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if n <= 0:
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raise ValueError("cannot compute logarithm of non-positive number")
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i = 0
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while n != 0:
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if (n & 1) and n != 1:
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raise ValueError("No solution could be found")
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i += 1
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n >>= 1
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i -= 1
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assert num == (1L << i)
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return i
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def exact_div(p, d, allow_divzero=False):
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"""Find and return an integer n such that p == n * d
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If no such integer exists, this function raises ValueError.
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Both operands must be integers.
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If the second operand is zero, this function will raise ZeroDivisionError
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unless allow_divzero is true (default: False).
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"""
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if not isinstance(p, (int, long)) or not isinstance(d, (int, long)):
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raise TypeError("unsupported operand type(s): %r and %r" % (type(p).__name__, type(d).__name__))
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if d == 0 and allow_divzero:
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n = 0
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if p != n * d:
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raise ValueError("No solution could be found")
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else:
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(n, r) = divmod(p, d)
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if r != 0:
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raise ValueError("No solution could be found")
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assert p == n * d
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return n
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# vim:set ts=4 sw=4 sts=4 expandtab:
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