Added a Python implementation

lfsr.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+# @file /home/mfukar/src/lfsr/lfsr.py
+# @author Michael Foukarakis
+# @version 1.0
+# @date Created: Thu Feb 03, 2011 08:19 GTB Standard Time
+# Last Update: Thu Feb 03, 2011 16:26 GTB Standard Time
+#------------------------------------------------------------------------
+# Description: Implementation of a Galois LFSR 
+# The bitstream is provided by the generator function
+# GLFSR.states(). The 'repeat' flag controls whether the
+# generator stops once the LFSR overflows or whether it
+# continues perpetually.
+#------------------------------------------------------------------------
+# History: None yet
+# TODO: Nothing yet
+#------------------------------------------------------------------------
+class GLFSR:
+ def __init__(self, polynomial, seed):
+ self.polynomial = polynomial | 1
+ self.seed = seed
+ self.data = seed
+ self.mask = 1
+
+ temp_mask = polynomial
+ while temp_mask != 0:
+ if temp_mask & self.mask != 0:
+ temp_mask = temp_mask ^ self.mask
+ if temp_mask == 0: break
+ self.mask = self.mask << 1
+
+ def states(self, repeat=False):
+ while True:
+ self.data = self.data << 1
+ if self.data & self.mask != 0:
+ self.data = self.data ^ self.polynomial
+ yield 1
+ else:
+ yield 0
+ if repeat == False and self.data == self.seed:
+ return