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"""prngd module
This module interfaces with PRNGD - Pseudo Random Number Generator
Daemon for platforms without /dev/random or /dev/urandom.
It is based on code from Stuart D. Gathman stuart at bmsi.com and is
Public Domain. The original code is available from
http://mail.python.org/pipermail/python-list/2002-November/170737.html"""
import socket
from struct import unpack,pack
class PRNGD:
"Provide access to the Portable Random Number Generator Daemon"
def __init__(self,sockname="/var/run/egd-pool"):
self.randfile = socket.socket(socket.AF_UNIX,socket.SOCK_STREAM)
self.randfile.connect(sockname)
def _readall(self,n):
s = self.randfile.recv(n)
while len(s) < n:
s = s + self.randfile.recv(n - len(s))
return s
def get(self):
"Return number of available bytes of entropy."
self.randfile.sendall('\x00')
return unpack(">i",self._readall(4))[0]
def read(self,cnt):
"Return available entropy, up to cnt bytes."
if cnt > 255: cnt = 255
self.randfile.sendall(pack("BB",0x01,cnt))
buf = self._readall(1)
assert len(buf) == 1
count = unpack("B",buf)[0]
buf = self._readall(count)
assert len(buf) == count, "didn't get all the entropy"
return buf
def readall(self,cnt):
"Return all entropy bytes requested"
if cnt < 256:
self.randfile.sendall(pack("BB",0x02,cnt))
return self._readall(cnt)
buf = readall(self,255)
cnt -= len(buf)
while cnt > 255:
buf += readall(self,255)
cnt -= len(buf)
return buf + readall(self,cnt)
def getpid(self):
"Return the process id string of the prngd"
self.randfile.sendall('\x04')
buf = self._readall(1)
assert len(buf) == 1
count = unpack("B",buf)[0]
buf = self._readall(count)
assert len(buf) == count, "didn't get whole PID string"
return buf
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