.\" 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. All advertising materials mentioning features or use of this software
-.\" must display the following acknowledgement:
-.\" This product includes software developed by the University of
-.\" California, Berkeley and its contributors.
.\" 4. 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.
.\" SUCH DAMAGE.
.\"
.\" @(#)random.3 8.1 (Berkeley) 6/4/93
-.\" $FreeBSD: src/lib/libc/stdlib/random.3,v 1.17 2001/09/07 14:46:36 asmodai Exp $
+.\" $FreeBSD: src/lib/libc/stdlib/random.3,v 1.22 2007/01/09 00:28:10 imp Exp $
.\"
.Dd June 4, 1993
.Dt RANDOM 3
.Os
.Sh NAME
+.Nm initstate ,
.Nm random ,
+.Nm setstate ,
.Nm srandom ,
-.Nm srandomdev ,
-.Nm initstate ,
-.Nm setstate
+.Nm srandomdev
.Nd better random number generator; routines for changing generators
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
+.Ft char *
+.Fo initstate
+.Fa "unsigned seed"
+.Fa "char *state"
+.Fa "size_t size"
+.Fc
.Ft long
-.Fn random void
+.Fo random
+.Fa void
+.Fc
+.Ft char *
+.Fo setstate
+.Fa "const char *state"
+.Fc
.Ft void
-.Fn srandom "unsigned long seed"
+.Fo srandom
+.Fa "unsigned seed"
+.Fc
.Ft void
-.Fn srandomdev void
-.Ft char *
-.Fn initstate "unsigned long seed" "char *state" "long n"
-.Ft char *
-.Fn setstate "char *state"
+.Fo srandomdev
+.Fa void
+.Fc
.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
+uses a non-linear, additive feedback, random number generator, employing a
+default table of size 31 long integers.
+It returns successive pseudo-random
numbers in the range from 0 to
.if t 2\u\s731\s10\d\(mi1.
.if n (2**31)\(mi1.
The difference is that
.Xr rand 3
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
+generated by rand go through a cyclic pattern.
+All of the bits generated by
.Fn random
-are usable. For example,
+are usable.
+For example,
.Sq Li random()&01
will produce a random binary
value.
.Pp
Like
+.Xr srand 3 ,
+.Fn srandom
+sets the initial seed value for future calls to
+.Fn random .
+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.
+with the same seed.
.Pp
The
.Fn srandomdev
-routine initialize a state array using
+routine initializes a state array, using the
.Xr random 4
random number device which returns good random numbers,
suitable for cryptographic use.
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
+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 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
+the random number sequence and provides for restarting at the same
point) is also an argument.
The
.Fn initstate
With 256 bytes of state information, the period of the random number
generator is greater than
.if t 2\u\s769\s10\d,
-.if n 2**69
+.if n 2**69 ,
which should be sufficient for most purposes.
-.Sh AUTHORS
-.An Earl T. Cohen
.Sh DIAGNOSTICS
If
.Fn initstate
.Fn setstate
detects that the state information has been garbled, error
messages are printed on the standard error output.
+.Sh LEGACY SYNOPSIS
+.Fd #include <stdlib.h>
+.Pp
+.Ft char *
+.br
+.Fo initstate
+.Fa "unsigned long seed"
+.Fa "char *state"
+.Fa "long size"
+.Fc ;
+.Pp
+.Ft char *
+.br
+.Fo setstate
+.Fa "char *state"
+.Fc ;
+.Pp
+.Ft void
+.br
+.Fo srandom
+.Fa "unsigned long seed"
+.Fc ;
+.Pp
+The type of each parameter is different in the legacy version.
.Sh SEE ALSO
+.Xr arc4random 3 ,
.Xr rand 3 ,
.Xr srand 3 ,
-.Xr random 4
+.Xr random 4 ,
+.Xr compat 5
.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 .
random sequence did not vary much with the seed.
The current implementation employs a better pseudo-random number
generator for the initial state calculation.
+.Pp
+Applications requiring cryptographic quality randomness should use
+.Xr arc4random 3 .
projects / apple / libc.git / blobdiff