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# Copyright 2002 by Katharine Lindner. All rights reserved.
# This code is part of the Biopython distribution and governed by its
# license. Please see the LICENSE file that should have been included
# as part of this package.
"""handles true random numbers supplied from the the web server of fourmilab. Based on
atmospheric noise. The motivation is to support biosimulations that rely on random numbers.
"""
import os
import sys
import string
from urllib import FancyURLopener
from urllib import urlencode
from Bio.SGMLExtractor import SGMLExtractorHandle
def hex_convert( text ):
num_val = 0L
text = text.lower()
for letter in text:
hex_digit = string.hexdigits.find( letter )
if( hex_digit < 0 ):
raise ValueError
num_val = ( num_val * 16 ) + hex_digit
return num_val
def byte_concat( text ):
val = 0
numbytes = len( text )
for i in range( 0, numbytes ):
val = val * 256
val = val + ord( text[ i ] )
return val
class HotCache:
def __init__( self ):
# self.url = 'http://www.fourmilab.ch/cgi-bin/uncgi/Hotbits?num=5000&min=1&max=6&col=1'
self.url = 'http://www.random.org/cgi-bin/randbyte?'
self.query = { 'nbytes' : 128, 'fmt' : 'h' }
self.fill_hot_cache()
def fill_hot_cache( self ):
bases = [ 'a', 'g', 'c', 't' ]
url = self.url + urlencode( self.query )
url_opener = FancyURLopener( )
fh = url_opener.open( url )
hot_rand_handle = SGMLExtractorHandle( fh, [ 'pre', ] )
hot_cache = fh.read()
self.hot_cache = hot_cache
fh.close()
return self.hot_cache
def next_num( self, num_digits = 4 ):
cache = self.hot_cache
numbytes = num_digits / 2
if( len( cache ) % numbytes != 0 ):
print 'len_cache is %d' % len( cache )
raise ValueError
if( cache == '' ):
self.fill_hot_cache()
cache = self.hot_cache
hexdigits = cache[ :numbytes ]
self.hot_cache = cache[ numbytes: ]
return byte_concat( hexdigits )
class HotRandom:
def __init__( self ):
self.hot_cache = HotCache( )
def hot_rand( self, high, low = 0 ):
span = high - low
val = self.hot_cache.next_num()
val = ( span * val ) >> 16
val = val + low
return val
if( __name__ == '__main__' ):
hot_random = HotRandom()
for j in range ( 0, 130 ):
print hot_random.hot_rand( 25 )
nums = [ '0000', 'abcd', '1234', '5555', '4321', 'aaaa', 'ffff' ]
for num in nums:
print hex_convert( num )
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