[apple/libc.git] / gen / FreeBSD / arc4random.c

/*
 * Copyright (c) 1996, David Mazieres <dm@uun.org>
 * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Arc4 random number generator for OpenBSD.
 *
 * This code is derived from section 17.1 of Applied Cryptography,
 * second edition, which describes a stream cipher allegedly
 * compatible with RSA Labs "RC4" cipher (the actual description of
 * which is a trade secret).  The same algorithm is used as a stream
 * cipher called "arcfour" in Tatu Ylonen's ssh package.
 *
 * Here the stream cipher has been modified always to include the time
 * when initializing the state.  That makes it impossible to
 * regenerate the same random sequence twice, so this can't be used
 * for encryption, but will generate good random numbers.
 *
 * RC4 is a registered trademark of RSA Laboratories.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/lib/libc/gen/arc4random.c,v 1.25 2008/09/09 09:46:36 ache Exp $");

#include "namespace.h"
#include <sys/types.h>
#include <sys/time.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>

#include "libc_private.h"
#include "un-namespace.h"

struct arc4_stream {
	u_int8_t i;
	u_int8_t j;
	u_int8_t s[256];
};

static int lock = 0;
extern void spin_lock(int*);
extern void spin_unlock(int*);

#define	RANDOMDEV	"/dev/random"
#define KEYSIZE		128
#define	THREAD_LOCK()						\
	do {							\
		if (__isthreaded)				\
			spin_lock(&lock);			\
	} while (0)

#define	THREAD_UNLOCK()						\
	do {							\
		if (__isthreaded)				\
			spin_unlock(&lock);			\
	} while (0)

static struct arc4_stream rs = {
	.i = 0,
	.j = 0,
	.s = {
		  0,   1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,
		 16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,  30,  31,
		 32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,
		 48,  49,  50,  51,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  62,  63,
		 64,  65,  66,  67,  68,  69,  70,  71,  72,  73,  74,  75,  76,  77,  78,  79,
		 80,  81,  82,  83,  84,  85,  86,  87,  88,  89,  90,  91,  92,  93,  94,  95,
		 96,  97,  98,  99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
		112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
		128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143,
		144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
		160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
		176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
		192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
		208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
		224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239,
		240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255
	}
};
static int rs_initialized;
static int rs_stired;
static int arc4_count;

static inline u_int8_t arc4_getbyte(void);
static void arc4_stir(void);

static struct {
	struct timeval	tv;
	pid_t		pid;
	u_int8_t	rnd[KEYSIZE];
} rdat;
static volatile int rs_data_available = 0;

static inline void
arc4_addrandom(u_char *dat, int datlen)
{
	int     n;
	u_int8_t si;

	rs.i--;
	for (n = 0; n < 256; n++) {
		rs.i = (rs.i + 1);
		si = rs.s[rs.i];
		rs.j = (rs.j + si + dat[n % datlen]);
		rs.s[rs.i] = rs.s[rs.j];
		rs.s[rs.j] = si;
	}
	rs.j = rs.i;
}

static void
arc4_fetch(void)
{
	int done, fd;
	fd = _open(RANDOMDEV, O_RDONLY, 0);
	done = 0;
	if (fd >= 0) {
		if (_read(fd, &rdat, KEYSIZE) == KEYSIZE)
			done = 1;
		(void)_close(fd);
	} 
	if (!done) {
		(void)gettimeofday(&rdat.tv, NULL);
		rdat.pid = getpid();
		/* We'll just take whatever was on the stack too... */
	}
}

static void
arc4_stir(void)
{
	int n;
	/*
	 * If we don't have data, we need some now before we can integrate
	 * it into the static buffers
	 */
	if (!rs_data_available)
	{
		arc4_fetch();
	}
	rs_data_available = 0;
	__sync_synchronize();

	arc4_addrandom((u_char *)&rdat, KEYSIZE);

	/*
	 * Throw away the first N bytes of output, as suggested in the
	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
	 * by Fluher, Mantin, and Shamir.  N=1024 is based on
	 * suggestions in the paper "(Not So) Random Shuffles of RC4"
	 * by Ilya Mironov.
	 */
	for (n = 0; n < 1024; n++)
		(void) arc4_getbyte();
	arc4_count = 1600000;
	rs_stired = 1;
}

static inline u_int8_t
arc4_getbyte(void)
{
	u_int8_t si, sj;

	rs.i = (rs.i + 1);
	si = rs.s[rs.i];
	rs.j = (rs.j + si);
	sj = rs.s[rs.j];
	rs.s[rs.i] = sj;
	rs.s[rs.j] = si;

	return (rs.s[(si + sj) & 0xff]);
}

static inline u_int32_t
arc4_getword(void)
{
	u_int32_t val;

	val = arc4_getbyte() << 24;
	val |= arc4_getbyte() << 16;
	val |= arc4_getbyte() << 8;
	val |= arc4_getbyte();

	return (val);
}

/* 7944700: force restir in child */
__private_extern__ void
_arc4_fork_child(void)
{
	rs_stired = 0;
	rs_data_available = 0;
}

static inline int
arc4_check_stir(void)
{
	if (!rs_stired || arc4_count <= 0) {
		arc4_stir();
		return 1;
	}
	return 0;
}

void
arc4random_stir(void)
{
	THREAD_LOCK();
	arc4_stir();
	THREAD_UNLOCK();
}

void
arc4random_addrandom(u_char *dat, int datlen)
{
	THREAD_LOCK();
	arc4_check_stir();
	arc4_addrandom(dat, datlen);
	THREAD_UNLOCK();
}

u_int32_t
arc4random(void)
{
	u_int32_t rnd;

	THREAD_LOCK();

	int did_stir = arc4_check_stir();
	rnd = arc4_getword();
	arc4_count -= 4;

	THREAD_UNLOCK();
	if (did_stir)
	{
		/* stirring used up our data pool, we need to read in new data outside of the lock */
		arc4_fetch();
		rs_data_available = 1;
		__sync_synchronize();
	}

	return (rnd);
}

void
arc4random_buf(void *_buf, size_t n)
{
	u_char *buf = (u_char *)_buf;
	int did_stir = 0;

	THREAD_LOCK();

	while (n--) {
		if (arc4_check_stir())
		{
			did_stir = 1;
		}
		buf[n] = arc4_getbyte();
		arc4_count--;
	}
	
	THREAD_UNLOCK();
	if (did_stir)
	{
		/* stirring used up our data pool, we need to read in new data outside of the lock */
		arc4_fetch();
		rs_data_available = 1;
		__sync_synchronize();
	}
}

/*
 * Calculate a uniformly distributed random number less than upper_bound
 * avoiding "modulo bias".
 *
 * Uniformity is achieved by generating new random numbers until the one
 * returned is outside the range [0, 2**32 % upper_bound).  This
 * guarantees the selected random number will be inside
 * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
 * after reduction modulo upper_bound.
 */
u_int32_t
arc4random_uniform(u_int32_t upper_bound)
{
	u_int32_t r, min;

	if (upper_bound < 2)
		return (0);

#if (ULONG_MAX > 0xffffffffUL)
	min = 0x100000000UL % upper_bound;
#else
	/* Calculate (2**32 % upper_bound) avoiding 64-bit math */
	if (upper_bound > 0x80000000)
		min = 1 + ~upper_bound;		/* 2**32 - upper_bound */
	else {
		/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
		min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
	}
#endif

	/*
	 * This could theoretically loop forever but each retry has
	 * p > 0.5 (worst case, usually far better) of selecting a
	 * number inside the range we need, so it should rarely need
	 * to re-roll.
	 */
	for (;;) {
		r = arc4random();
		if (r >= min)
			break;
	}

	return (r % upper_bound);
}

#if 0
/*-------- Test code for i386 --------*/
#include <stdio.h>
#include <machine/pctr.h>
int
main(int argc, char **argv)
{
	const int iter = 1000000;
	int     i;
	pctrval v;

	v = rdtsc();
	for (i = 0; i < iter; i++)
		arc4random();
	v = rdtsc() - v;
	v /= iter;

	printf("%qd cycles\n", v);
}
#endif
Commit	Line	Data
5b2abdfb	1	/*
1f2f436a A	2	* Copyright (c) 1996, David Mazieres <dm@uun.org>
	3	* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
	4	*
	5	* Permission to use, copy, modify, and distribute this software for any
	6	* purpose with or without fee is hereby granted, provided that the above
	7	* copyright notice and this permission notice appear in all copies.
5b2abdfb	8	*
1f2f436a A	9	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	15	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
5b2abdfb A	16	*/
	17
	18	/*
1f2f436a A	19	* Arc4 random number generator for OpenBSD.
1f2f436a A	20	*
5b2abdfb A	21	* This code is derived from section 17.1 of Applied Cryptography,
	22	* second edition, which describes a stream cipher allegedly
	23	* compatible with RSA Labs "RC4" cipher (the actual description of
	24	* which is a trade secret). The same algorithm is used as a stream
	25	* cipher called "arcfour" in Tatu Ylonen's ssh package.
	26	*
	27	* Here the stream cipher has been modified always to include the time
	28	* when initializing the state. That makes it impossible to
	29	* regenerate the same random sequence twice, so this can't be used
	30	* for encryption, but will generate good random numbers.
	31	*
	32	* RC4 is a registered trademark of RSA Laboratories.
	33	*/
	34
224c7076	35	#include <sys/cdefs.h>
1f2f436a	36	__FBSDID("$FreeBSD: src/lib/libc/gen/arc4random.c,v 1.25 2008/09/09 09:46:36 ache Exp $");
224c7076 A	37
	38	#include "namespace.h"
	39	#include <sys/types.h>
	40	#include <sys/time.h>
5b2abdfb A	41	#include <stdlib.h>
	42	#include <fcntl.h>
	43	#include <unistd.h>
224c7076 A	44	#include <pthread.h>
	45
	46	#include "libc_private.h"
	47	#include "un-namespace.h"
5b2abdfb A	48
	49	struct arc4_stream {
	50	u_int8_t i;
	51	u_int8_t j;
	52	u_int8_t s[256];
	53	};
	54
1f2f436a A	55	static int lock = 0;
	56	extern void spin_lock(int*);
	57	extern void spin_unlock(int*);
224c7076	58
1f2f436a A	59	#define RANDOMDEV "/dev/random"
1f2f436a A	60	#define KEYSIZE 128
224c7076 A	61	#define THREAD_LOCK() \
	62	do { \
	63	if (__isthreaded) \
1f2f436a	64	spin_lock(&lock); \
224c7076 A	65	} while (0)
	66
	67	#define THREAD_UNLOCK() \
	68	do { \
	69	if (__isthreaded) \
1f2f436a	70	spin_unlock(&lock); \
224c7076 A	71	} while (0)
224c7076 A	72
1f2f436a A	73	static struct arc4_stream rs = {
	74	.i = 0,
	75	.j = 0,
	76	.s = {
	77	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
	78	16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
	79	32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
	80	48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
	81	64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
	82	80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,
	83	96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
	84	112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
	85	128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143,
	86	144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
	87	160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
	88	176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
	89	192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
	90	208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
	91	224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239,
	92	240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255
	93	}
	94	};
5b2abdfb	95	static int rs_initialized;
224c7076	96	static int rs_stired;
1f2f436a	97	static int arc4_count;
224c7076	98
1f2f436a A	99	static inline u_int8_t arc4_getbyte(void);
1f2f436a A	100	static void arc4_stir(void);
5b2abdfb	101
1f2f436a A	102	static struct {
	103	struct timeval tv;
	104	pid_t pid;
	105	u_int8_t rnd[KEYSIZE];
	106	} rdat;
	107	static volatile int rs_data_available = 0;
5b2abdfb A	108
5b2abdfb A	109	static inline void
1f2f436a	110	arc4_addrandom(u_char *dat, int datlen)
5b2abdfb A	111	{
	112	int n;
	113	u_int8_t si;
	114
1f2f436a	115	rs.i--;
5b2abdfb	116	for (n = 0; n < 256; n++) {
1f2f436a A	117	rs.i = (rs.i + 1);
	118	si = rs.s[rs.i];
	119	rs.j = (rs.j + si + dat[n % datlen]);
	120	rs.s[rs.i] = rs.s[rs.j];
	121	rs.s[rs.j] = si;
5b2abdfb	122	}
1f2f436a	123	rs.j = rs.i;
5b2abdfb A	124	}
	125
	126	static void
1f2f436a	127	arc4_fetch(void)
5b2abdfb	128	{
1f2f436a	129	int done, fd;
224c7076	130	fd = _open(RANDOMDEV, O_RDONLY, 0);
1f2f436a	131	done = 0;
5b2abdfb	132	if (fd >= 0) {
1f2f436a A	133	if (_read(fd, &rdat, KEYSIZE) == KEYSIZE)
	134	done = 1;
	135	(void)_close(fd);
224c7076	136	}
1f2f436a A	137	if (!done) {
	138	(void)gettimeofday(&rdat.tv, NULL);
	139	rdat.pid = getpid();
	140	/* We'll just take whatever was on the stack too... */
	141	}
	142	}
5b2abdfb	143
1f2f436a A	144	static void
	145	arc4_stir(void)
	146	{
	147	int n;
	148	/*
	149	* If we don't have data, we need some now before we can integrate
	150	* it into the static buffers
	151	*/
	152	if (!rs_data_available)
	153	{
	154	arc4_fetch();
	155	}
	156	rs_data_available = 0;
	157	__sync_synchronize();
	158
	159	arc4_addrandom((u_char *)&rdat, KEYSIZE);
224c7076 A	160
	161	/*
	162	* Throw away the first N bytes of output, as suggested in the
	163	* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
	164	* by Fluher, Mantin, and Shamir. N=1024 is based on
	165	* suggestions in the paper "(Not So) Random Shuffles of RC4"
	166	* by Ilya Mironov.
	167	*/
	168	for (n = 0; n < 1024; n++)
1f2f436a A	169	(void) arc4_getbyte();
	170	arc4_count = 1600000;
	171	rs_stired = 1;
5b2abdfb A	172	}
	173
	174	static inline u_int8_t
1f2f436a	175	arc4_getbyte(void)
5b2abdfb A	176	{
	177	u_int8_t si, sj;
	178
1f2f436a A	179	rs.i = (rs.i + 1);
	180	si = rs.s[rs.i];
	181	rs.j = (rs.j + si);
	182	sj = rs.s[rs.j];
	183	rs.s[rs.i] = sj;
	184	rs.s[rs.j] = si;
224c7076	185
1f2f436a	186	return (rs.s[(si + sj) & 0xff]);
5b2abdfb A	187	}
	188
	189	static inline u_int32_t
1f2f436a	190	arc4_getword(void)
5b2abdfb A	191	{
5b2abdfb A	192	u_int32_t val;
224c7076	193
1f2f436a A	194	val = arc4_getbyte() << 24;
	195	val \|= arc4_getbyte() << 16;
	196	val \|= arc4_getbyte() << 8;
	197	val \|= arc4_getbyte();
224c7076 A	198
224c7076 A	199	return (val);
5b2abdfb A	200	}
5b2abdfb A	201
1f2f436a A	202	/* 7944700: force restir in child */
	203	__private_extern__ void
	204	_arc4_fork_child(void)
5b2abdfb	205	{
1f2f436a A	206	rs_stired = 0;
1f2f436a A	207	rs_data_available = 0;
224c7076 A	208	}
224c7076 A	209
1f2f436a	210	static inline int
224c7076 A	211	arc4_check_stir(void)
224c7076 A	212	{
1f2f436a A	213	if (!rs_stired \|\| arc4_count <= 0) {
	214	arc4_stir();
	215	return 1;
224c7076	216	}
1f2f436a	217	return 0;
224c7076 A	218	}
	219
	220	void
1f2f436a	221	arc4random_stir(void)
224c7076 A	222	{
224c7076 A	223	THREAD_LOCK();
1f2f436a	224	arc4_stir();
224c7076	225	THREAD_UNLOCK();
5b2abdfb A	226	}
	227
	228	void
1f2f436a	229	arc4random_addrandom(u_char *dat, int datlen)
5b2abdfb	230	{
224c7076	231	THREAD_LOCK();
224c7076	232	arc4_check_stir();
1f2f436a	233	arc4_addrandom(dat, datlen);
224c7076	234	THREAD_UNLOCK();
5b2abdfb A	235	}
	236
	237	u_int32_t
1f2f436a	238	arc4random(void)
5b2abdfb	239	{
224c7076 A	240	u_int32_t rnd;
	241
	242	THREAD_LOCK();
1f2f436a A	243
	244	int did_stir = arc4_check_stir();
	245	rnd = arc4_getword();
	246	arc4_count -= 4;
	247
224c7076	248	THREAD_UNLOCK();
1f2f436a A	249	if (did_stir)
	250	{
	251	/* stirring used up our data pool, we need to read in new data outside of the lock */
	252	arc4_fetch();
	253	rs_data_available = 1;
	254	__sync_synchronize();
	255	}
224c7076 A	256
224c7076 A	257	return (rnd);
5b2abdfb A	258	}
5b2abdfb A	259
1f2f436a A	260	void
	261	arc4random_buf(void *_buf, size_t n)
	262	{
	263	u_char buf = (u_char )_buf;
	264	int did_stir = 0;
	265
	266	THREAD_LOCK();
	267
	268	while (n--) {
	269	if (arc4_check_stir())
	270	{
	271	did_stir = 1;
	272	}
	273	buf[n] = arc4_getbyte();
	274	arc4_count--;
	275	}
	276
	277	THREAD_UNLOCK();
	278	if (did_stir)
	279	{
	280	/* stirring used up our data pool, we need to read in new data outside of the lock */
	281	arc4_fetch();
	282	rs_data_available = 1;
	283	__sync_synchronize();
	284	}
	285	}
	286
	287	/*
	288	* Calculate a uniformly distributed random number less than upper_bound
	289	* avoiding "modulo bias".
	290	*
	291	* Uniformity is achieved by generating new random numbers until the one
	292	* returned is outside the range [0, 2**32 % upper_bound). This
	293	* guarantees the selected random number will be inside
	294	* [232 % upper_bound, 232) which maps back to [0, upper_bound)
	295	* after reduction modulo upper_bound.
	296	*/
	297	u_int32_t
	298	arc4random_uniform(u_int32_t upper_bound)
	299	{
	300	u_int32_t r, min;
	301
	302	if (upper_bound < 2)
	303	return (0);
	304
	305	#if (ULONG_MAX > 0xffffffffUL)
	306	min = 0x100000000UL % upper_bound;
	307	#else
	308	/* Calculate (2*32 % upper_bound) avoiding 64-bit math /
	309	if (upper_bound > 0x80000000)
	310	min = 1 + ~upper_bound; /* 2*32 - upper_bound /
	311	else {
	312	/* (2*32 - (x 2)) % x == 232 % x when x <= 231 */
	313	min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
	314	}
	315	#endif
	316
	317	/*
	318	* This could theoretically loop forever but each retry has
	319	* p > 0.5 (worst case, usually far better) of selecting a
	320	* number inside the range we need, so it should rarely need
	321	* to re-roll.
	322	*/
	323	for (;;) {
324	r = arc4random();
325	if (r >= min)
326	break;
327	}
328
329	return (r % upper_bound);
330	}
331
5b2abdfb A	332	#if 0
	333	/-------- Test code for i386 --------/
	334	#include <stdio.h>
	335	#include <machine/pctr.h>
	336	int
	337	main(int argc, char **argv)
	338	{
	339	const int iter = 1000000;
	340	int i;
	341	pctrval v;
	342
	343	v = rdtsc();
	344	for (i = 0; i < iter; i++)
	345	arc4random();
	346	v = rdtsc() - v;
	347	v /= iter;
	348
	349	printf("%qd cycles\n", v);
	350	}
	351	#endif