# Copyright (C) 2009 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

import time

class EntropyPool(object):
    def __init__(self, seed=None):
        self.pool_index = 0
        self.digest = None
        self.next_byte = 0
        if seed is None:
            try:
                r = file('/dev/random')
                try:
                    seed = r.read(16)
                finally:
                    r.close()
            except:
                seed = str(time.time())
        try:
            import hashlib
            self.hash = hashlib.sha1()
            self.hash_len = 20
        except:
            try:
                import sha
                self.hash = sha.new()
                self.hash_len = 20
            except:
                import md5
                self.hash = md5.new()
                self.hash_len = 16
        self.pool = '\0' * self.hash_len
        self.stir(seed)

    def stir(self, entropy):
        bytes = [ord(c) for c in self.pool]
        for c in entropy:
            if self.pool_index == self.hash_len or self.pool_index >= len(bytes):
                self.pool_index = 0
            b = ord(c) & 0xff
            try:
                bytes[self.pool_index] ^= b
            except IndexError:
                pass
#                print "[stir] pool index: %s len bytes: %s" % (self.pool_index, len(bytes))
            self.pool_index += 1
        self.pool = ''.join([chr(c) for c in bytes])

    def random_8(self):
        if self.digest is None or self.next_byte == self.hash_len or self.next_byte >= len(self.digest):
            self.hash.update(self.pool)
            self.digest = self.hash.digest()
            self.stir(self.digest)
            self.next_byte = 0

	# I'm not sure why the if statement above isn't triggering here.
	try:
            value = ord(self.digest[self.next_byte])
	except IndexError:
#	    print "forcing stir [dlen=%s next=%s]" % (len(self.digest), self.next_byte)
            self.hash.update(self.pool)
            self.digest = self.hash.digest()
            self.stir(self.digest)
            self.next_byte = 0
            value = ord(self.digest[self.next_byte])
	    
        self.next_byte += 1
        return value

    def random_16(self):
        return self.random_8() * 256 + self.random_8()

    def random_32(self):
        return self.random_16() * 65536 + self.random_16()

    def random_between(self, first, last):
        size = last - first + 1
        if size > 4294967296L:
            raise ValueError, 'too big'
        if size > 65536:
            rand = self.random_32
            max = 4294967295L
        elif size > 256:
            rand = self.random_16
            max = 65535
        else:
            rand = self.random_8
            max = 255
	return (first + size * rand() // (max + 1))

pool = EntropyPool()

def random_16():
    return pool.random_16()

def between(first, last):
    return pool.random_between(first, last)

@@ -1785,16 +1785,18 @@
 n(bytes)
+-1
 :%0A      
@@ -1855,37 +1855,16 @@
  & 0xff%0A
-            try:%0A    
         
@@ -1899,153 +1899,8 @@
 = b%0A
-            except IndexError:%0A                pass%0A#                print %22%5Bstir%5D pool index: %25s len bytes: %25s%22 %25 (self.pool_index, len(bytes))%0A
     
@@ -2113,388 +2113,11 @@
 est)
-:%0A            self.hash.update(self.pool)%0A            self.digest = self.hash.digest()%0A            self.stir(self.digest)%0A            self.next_byte = 0%0A%0A%09# I'm not sure why the if statement above isn't triggering here.%0A%09try:%0A            value = ord(self.digest%5Bself.next_byte%5D)%0A%09except IndexError:%0A#%09    print %22forcing stir %5Bdlen=%25s next=%25s%5D%22 %25 (len(self.digest), self.next_byte)
+-1:
 %0A   
@@ -2268,24 +2268,29 @@
 = 0%0A        
+%0A    
     value = 
@@ -2326,14 +2326,8 @@
 e%5D)%0A
-%09    %0A
     

Improve our entropy.py patch in preparation for submission