Simplify _rand_exp

[jvoisin]

The current _rand_exp is currently looking suboptimal:

 # Exp2 generates n with probability 1/2^(n+1). 
 @staticmethod 
 def _rand_exp(): 
 rand_bin = bin(int(random.random() * 2**32-1))[2:] 
 rand_bin = '0'*(32 - len(rand_bin)) + rand_bin 
 count = 0 
 for i in rand_bin: 
 if i == '0': 
 count +=1 
 else: 
 break 
 return count

Am I misreading the code and the comment, or is it equivalent to int(random.expovariate(0.5))?

[yevgenypats]

_rand_exp generates a number from 0-32 I'm don't see how it's equivalent to int(random.expovariate(0.5)) but maybe I'm missing something. I also searched a better way to implement this when I ported this part from go-fuzz but didn't find anything "built-in"

[jvoisin]

Then the comment above the function should be fixed/improved I think :)