[Jython-checkins] SF.net SVN: jython:[5303] trunk/jython/Lib/random.py

[<le...@us...>]

Revision: 5303
          http://jython.svn.sourceforge.net/jython/?rev=5303&view=rev
Author:   leosoto
Date:     2008-09-08 17:48:28 +0000 (Mon, 08 Sep 2008)

Log Message:
-----------
SystemRandom implementation taken from CPython. It depends on urandom(), which seems supported now through jna-posix

Modified Paths:
--------------
    trunk/jython/Lib/random.py

Modified: trunk/jython/Lib/random.py
===================================================================
--- trunk/jython/Lib/random.py	2008-09-08 14:41:41 UTC (rev 5302)
+++ trunk/jython/Lib/random.py	2008-09-08 17:48:28 UTC (rev 5303)
@@ -43,7 +43,10 @@
 from math import log as _log, exp as _exp, pi as _pi, e as _e
 from math import sqrt as _sqrt, acos as _acos, cos as _cos, sin as _sin
 from math import floor as _floor
+from os import urandom as _urandom
+from binascii import hexlify as _hexlify
 
+
 __all__ = ["Random","seed","random","uniform","randint","choice","sample",
            "randrange","shuffle","normalvariate","lognormvariate",
            "cunifvariate","expovariate","vonmisesvariate","gammavariate",
@@ -55,6 +58,7 @@
 LOG4 = _log(4.0)
 SG_MAGICCONST = 1.0 + _log(4.5)
 BPF = 53        # Number of bits in a float
+RECIP_BPF = 2**-BPF
 
 # Translated by Guido van Rossum from C source provided by
 # Adrian Baddeley.  Adapted by Raymond Hettinger for use with
@@ -768,24 +772,37 @@
 ## --------------- Operating System Random Source  ------------------
 
 class SystemRandom(Random):
+    """Alternate random number generator using sources provided
+    by the operating system (such as /dev/urandom on Unix or
+    CryptGenRandom on Windows).
+
+     Not available on all systems (see os.urandom() for details).
     """
-    XXX: throw NotImplementedError for any attemt to use this for now.
-    """
 
     def random(self):
-        self._notimplemented()
+        """Get the next random number in the range [0.0, 1.0)."""
+        return (long(_hexlify(_urandom(7)), 16) >> 3) * RECIP_BPF
 
     def getrandbits(self, k):
-        self._notimplemented()
+        """getrandbits(k) -> x.  Generates a long int with k random bits."""
+        if k <= 0:
+            raise ValueError('number of bits must be greater than zero')
+        if k != int(k):
+            raise TypeError('number of bits should be an integer')
+        bytes = (k + 7) // 8                    # bits / 8 and rounded up
+        x = long(_hexlify(_urandom(bytes)), 16)
+        return x >> (bytes * 8 - k)             # trim excess bits
 
     def _stub(self, *args, **kwds):
-        self._notimplemented()
+        "Stub method.  Not used for a system random number generator."
+        return None
+    seed = jumpahead = _stub
 
     def _notimplemented(self, *args, **kwds):
-        raise NotImplementedError('SystemRandom not implemented on Jython.')
+        "Method should not be called for a system random number generator."
+        raise NotImplementedError('System entropy source does not have state.')
     getstate = setstate = _notimplemented
 
-
 ## -------------------- test program --------------------
 
 def _test_generator(n, funccall):


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