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);
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, then 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.

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: http://www.mirbsd.org/man/arc4random.3

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

COPYRIGHT AND LICENSE

Copyright (c) 2008 Thorsten "mirabilos" Glaser

This module is covered by the 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.