BSD::arc4random(3p)

NAME
BSD::arc4random - Perl interface to the arc4 random number generator

SYNOPSIS
  use BSD::arc4random qw(:all);
  $v = arc4random();
  $v = arc4random_uniform($hz);
  if (!BSD::arc4random::have_kintf()) {
    $v = arc4random_addrandom("entropy to pass to the system");
  } else {
    $v = arc4random_pushb("entropy to pass to the system");
    $v = arc4random_pushk("entropy to pass to the kernel");
  }
  $s = arc4random_bytes(16, "entropy to pass to libc");
  arc4random_stir();
  $s = arc4random_bytes(16);
  print $RANDOM;

DESCRIPTION
This set of functions maps the arc4random(3) family of libc functions into Perl code. All functions listed below are ithreads-safe. The internal XS functions are not, but you are not supposed to call them, either.

On module load, perl's internal PRNG is re-seeded, as a bonus, using srand with an argument calculated from using arc4random_pushb on some entropy returned from rand's previous state.

  LOW-LEVEL FUNCTIONS

arc4random()
    This function returns an unsigned 32-bit integer random value.

arc4random_addrandom(pbuf)
    This function adds the entropy from pbuf into the libc pool and returns an unsigned 32-bit integer random value from it.

arc4random_pushb(pbuf)
    This function first pushes the pbuf argument to the kernel if possible, then the entropy returned by the kernel into the libc pool, then returns an unsigned 32-bit integer random value from it.

arc4random_pushk(pbuf)
    This function first pushes the pbuf argument to the kernel if possible, then returns an unsigned 32-bit integer random value from the kernel.

    This function is deprecated. Use arc4random_pushb instead.

arc4random_stir()
    This procedure attempts to retrieve new entropy from the kernel and add it to the libc pool. Usually, this means you must have access to the urandom(4) device; create it inside chroot(2) jails first if you use them.

have_kintf()
    This constant function returns 1 if arc4random_pushb and/or arc4random_pushk actually call the kernel interfaces, 0 if they merely map to arc4random_addrandom instead.

  HIGH-LEVEL FUNCTIONS

arc4random_bytes(num[, pbuf])
    This function returns a string containing as many random bytes as requested by the integral argument num. An optional pbuf argument is passed to the system first.

arc4random_uniform(upper_bound)
    Calculate a uniformly distributed random number less than upper_bound avoiding "modulo bias".

  PACKAGE VARIABLES

$RANDOM
    The $RANDOM returns a random value in the range [0; 32767] on each read attempt and pushes any value it is assigned to the kernel. It is tied at module load time.

tie variable, 'BSD::arc4random'[, max]
    You can tie any scalar variable to this package; the max argument is the maximum number returned; if undefined, 0 or >= 0xFFFFFFFF, no bound is used, and values in the range [0; 2**32-1] are returned. They will behave like $RANDOM.

AUTHOR
Thorsten Glaser <tg@mirbsd.de>

SEE ALSO
The arc4random(3) manual page, available online at: <https://www.mirbsd.org/man/arc4random.3>

Perl's rand and srand functions via perlfunc and perlfaq4.

The randex.pl plugin for Irssi, implementing the MirOS RANDEX protocol (entropy exchange over IRC), with CVSweb at: <http://cvs.mirbsd.de/ports/net/irssi/files/randex.pl>

<https://www.mirbsd.org/a4rp5bsd.htm> when it's done being written.

COPYRIGHT AND LICENSE
Copyright (c) 2008, 2009 Thorsten "mirabilos" Glaser Copyright (c) 2009 Benny Siegert

This module is covered by the MirOS Licence: http://mirbsd.de/MirOS-Licence <http://mirbsd.de/MirOS-Licence>

The original C implementation of arc4random_uniform was contributed by Damien Miller from OpenBSD, with simplifications by Jinmei Tatuya.