1 files changed, 186 insertions, 0 deletions

diff --git a/src/lib/libc/stdlib/random.3 b/src/lib/libc/stdlib/random.3
new file mode 100644
index 0000000000..f43f06420d
--- /dev/null
+++ b/src/lib/libc/stdlib/random.3
@@ -0,0 +1,186 @@
+.\" Copyright (c) 1983, 1991 The Regents of the University of California.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     $OpenBSD: random.3,v 1.17 2003/06/02 20:18:38 millert Exp $
+.\"
+.Dd April 19, 1991
+.Dt RANDOM 3
+.Os
+.Sh NAME
+.Nm random ,
+.Nm srandom ,
+.Nm srandomdev ,
+.Nm initstate ,
+.Nm setstate
+.Nd better random number generator; routines for changing generators
+.Sh SYNOPSIS
+.Fd #include <stdlib.h>
+.Ft long
+.Fn random void
+.Ft void
+.Fn srandom "unsigned int seed"
+.Ft void
+.Fn srandomdev void
+.Ft char *
+.Fn initstate "unsigned int seed" "char *state" "size_t n"
+.Ft char *
+.Fn setstate "const char *state"
+.Sh DESCRIPTION
+The
+.Fn random
+function uses a non-linear additive feedback random number generator employing
+a default table of size 31 long integers to return successive pseudo-random
+numbers in the range from 0 to (2**31)\-1.
+The period of this random number generator is very large, approximately
+16*((2**31)\-1).
+.Pp
+The
+.Fn random
+and
+.Fn srandom
+functions have (almost) the same calling sequence and initialization
+properties as
+.Xr rand 3 Ns / Ns Xr srand 3 .
+The difference is that
+.Xr rand
+produces a much less random sequence \(em in fact, the low dozen bits
+generated by rand go through a cyclic pattern.
+All the bits generated by
+.Fn random
+are usable.
+For example,
+.Sq Li random()&01
+will produce a random binary
+value.
+.Pp
+Like
+.Xr rand 3 ,
+.Fn random
+will by default produce a sequence of numbers that can be duplicated
+by calling
+.Fn srandom
+with
+.Ql 1
+as the seed.
+.Pp
+The
+.Fn srandomdev
+routine initializes a state array using the
+.Xr arandom 4
+random number device which returns good random numbers,
+suitable for cryptographic use.
+Note that this particular seeding procedure can generate
+states which are impossible to reproduce by calling
+.Fn srandom
+with any value, since the succeeding terms in the
+state buffer are no longer derived from the LC algorithm applied to
+a fixed seed.
+.Pp
+The
+.Fn initstate
+routine allows a state array, passed in as an argument, to be initialized
+for future use.
+The size of the state array (in bytes) is used by
+.Fn initstate
+to decide how sophisticated a random number generator it should use \(em the
+more state, the better the random numbers will be.
+(Current "optimal" values for the amount of state information are
+8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to
+the nearest known amount.
+Using less than 8 bytes will cause an error.)
+The seed for the initialization (which specifies a starting point for
+the random number sequence, and provides for restarting at the same
+point) is also an argument.
+The
+.Fn initstate
+function returns a pointer to the previous state information array.
+.Pp
+Once a state has been initialized, the
+.Fn setstate
+routine provides for rapid switching between states.
+The
+.Fn setstate
+function returns a pointer to the previous state array; its
+argument state array is used for further random number generation
+until the next call to
+.Fn initstate
+or
+.Fn setstate .
+.Pp
+Once a state array has been initialized, it may be restarted at a
+different point either by calling
+.Fn initstate
+(with the desired seed, the state array, and its size) or by calling
+both
+.Fn setstate
+(with the state array) and
+.Fn srandom
+(with the desired seed).
+The advantage of calling both
+.Fn setstate
+and
+.Fn srandom
+is that the size of the state array does not have to be remembered after
+it is initialized.
+.Pp
+With 256 bytes of state information, the period of the random number
+generator is greater than 2**69
+which should be sufficient for most purposes.
+.Sh DIAGNOSTICS
+If
+.Fn initstate
+is called with less than 8 bytes of state information, or if
+.Fn setstate
+detects that the state information has been garbled, error
+messages are printed on the standard error output.
+.Sh SEE ALSO
+.Xr arc4random 3 ,
+.Xr drand48 3 ,
+.Xr rand 3 ,
+.Xr random 4
+.Sh STANDARDS
+The
+.Fn random ,
+.Fn srandom ,
+.Fn initstate ,
+and
+.Fn setstate
+functions conform to
+.St -xpg4.2 .
+.Pp
+The
+.Fn srandomdev
+function is an extension.
+.Sh HISTORY
+These
+functions appeared in
+.Bx 4.2 .
+.Sh AUTHORS
+.An Earl T. Cohen
+.Sh BUGS
+About 2/3 the speed of
+.Xr rand 3 .