Source code for pytomo.dns.entropy

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import os
import time
try:
    import threading as _threading
except ImportError:
    import dummy_threading as _threading

[docs]class EntropyPool(object): def __init__(self, seed=None): self.pool_index = 0 self.digest = None self.next_byte = 0 self.lock = _threading.Lock() 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 if not seed is None: self.stir(seed) self.seeded = True else: self.seeded = False
[docs] def stir(self, entropy, already_locked=False): if not already_locked: self.lock.acquire() try: bytes = [ord(c) for c in self.pool] for c in entropy: if self.pool_index == self.hash_len: self.pool_index = 0 b = ord(c) & 0xff bytes[self.pool_index] ^= b self.pool_index += 1 self.pool = ''.join([chr(c) for c in bytes]) finally: if not already_locked: self.lock.release()
def _maybe_seed(self): if not self.seeded: try: seed = os.urandom(16) except: try: r = file('/dev/urandom', 'r', 0) try: seed = r.read(16) finally: r.close() except: seed = str(time.time()) self.seeded = True self.stir(seed, True)
[docs] def random_8(self): self.lock.acquire() self._maybe_seed() try: if self.digest is None or self.next_byte == self.hash_len: self.hash.update(self.pool) self.digest = self.hash.digest() self.stir(self.digest, True) self.next_byte = 0 value = ord(self.digest[self.next_byte]) self.next_byte += 1 finally: self.lock.release() return value
[docs] def random_16(self): return self.random_8() * 256 + self.random_8()
[docs] def random_32(self): return self.random_16() * 65536 + self.random_16()
[docs] 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()
[docs]def random_16(): return pool.random_16()
[docs]def between(first, last): return pool.random_between(first, last)