aboutsummaryrefslogtreecommitdiff
path: root/frozen_deps/Crypto/Util/_number_new.py
diff options
context:
space:
mode:
Diffstat (limited to 'frozen_deps/Crypto/Util/_number_new.py')
-rw-r--r--frozen_deps/Crypto/Util/_number_new.py119
1 files changed, 119 insertions, 0 deletions
diff --git a/frozen_deps/Crypto/Util/_number_new.py b/frozen_deps/Crypto/Util/_number_new.py
new file mode 100644
index 0000000..5f29176
--- /dev/null
+++ b/frozen_deps/Crypto/Util/_number_new.py
@@ -0,0 +1,119 @@
+# -*- coding: ascii -*-
+#
+# Util/_number_new.py : utility functions
+#
+# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain. To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+## NOTE: Do not import this module directly. Import these functions from Crypto.Util.number.
+
+__revision__ = "$Id$"
+__all__ = ['ceil_shift', 'ceil_div', 'floor_div', 'exact_log2', 'exact_div']
+
+import sys
+if sys.version_info[0] == 2 and sys.version_info[1] == 1:
+ from Crypto.Util.py21compat import *
+
+def ceil_shift(n, b):
+ """Return ceil(n / 2**b) without performing any floating-point or division operations.
+
+ This is done by right-shifting n by b bits and incrementing the result by 1
+ if any '1' bits were shifted out.
+ """
+ if not isinstance(n, int) or not isinstance(b, int):
+ raise TypeError("unsupported operand type(s): %r and %r" % (type(n).__name__, type(b).__name__))
+
+ assert n >= 0 and b >= 0 # I haven't tested or even thought about negative values
+ mask = (1 << b) - 1
+ if n & mask:
+ return (n >> b) + 1
+ else:
+ return n >> b
+
+def ceil_div(a, b):
+ """Return ceil(a / b) without performing any floating-point operations."""
+
+ if not isinstance(a, int) or not isinstance(b, int):
+ raise TypeError("unsupported operand type(s): %r and %r" % (type(a).__name__, type(b).__name__))
+
+ (q, r) = divmod(a, b)
+ if r:
+ return q + 1
+ else:
+ return q
+
+def floor_div(a, b):
+ if not isinstance(a, int) or not isinstance(b, int):
+ raise TypeError("unsupported operand type(s): %r and %r" % (type(a).__name__, type(b).__name__))
+
+ (q, r) = divmod(a, b)
+ return q
+
+def exact_log2(num):
+ """Find and return an integer i >= 0 such that num == 2**i.
+
+ If no such integer exists, this function raises ValueError.
+ """
+
+ if not isinstance(num, int):
+ raise TypeError("unsupported operand type: %r" % (type(num).__name__,))
+
+ n = int(num)
+ if n <= 0:
+ raise ValueError("cannot compute logarithm of non-positive number")
+
+ i = 0
+ while n != 0:
+ if (n & 1) and n != 1:
+ raise ValueError("No solution could be found")
+ i += 1
+ n >>= 1
+ i -= 1
+
+ assert num == (1 << i)
+ return i
+
+def exact_div(p, d, allow_divzero=False):
+ """Find and return an integer n such that p == n * d
+
+ If no such integer exists, this function raises ValueError.
+
+ Both operands must be integers.
+
+ If the second operand is zero, this function will raise ZeroDivisionError
+ unless allow_divzero is true (default: False).
+ """
+
+ if not isinstance(p, int) or not isinstance(d, int):
+ raise TypeError("unsupported operand type(s): %r and %r" % (type(p).__name__, type(d).__name__))
+
+ if d == 0 and allow_divzero:
+ n = 0
+ if p != n * d:
+ raise ValueError("No solution could be found")
+ else:
+ (n, r) = divmod(p, d)
+ if r != 0:
+ raise ValueError("No solution could be found")
+
+ assert p == n * d
+ return n
+
+# vim:set ts=4 sw=4 sts=4 expandtab: