/contrib/bind9/lib/isc/random.c
https://bitbucket.org/freebsd/freebsd-head/ · C · 113 lines · 66 code · 19 blank · 28 comment · 8 complexity · e2c1837368d0d4d17dadc67e47e51630 MD5 · raw file
- /*
- * Copyright (C) 2004, 2005, 2007, 2009 Internet Systems Consortium, Inc. ("ISC")
- * Copyright (C) 1999-2003 Internet Software Consortium.
- *
- * Permission to use, copy, modify, and/or 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 ISC DISCLAIMS ALL WARRANTIES WITH
- * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
- * AND FITNESS. IN NO EVENT SHALL ISC 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.
- */
- /* $Id: random.c,v 1.28 2009/07/16 05:52:46 marka Exp $ */
- /*! \file */
- #include <config.h>
- #include <stdlib.h>
- #include <time.h> /* Required for time(). */
- #ifdef HAVE_SYS_TYPES_H
- #include <sys/types.h>
- #endif
- #ifdef HAVE_UNISTD_H
- #include <unistd.h>
- #endif
- #include <isc/mutex.h>
- #include <isc/once.h>
- #include <isc/random.h>
- #include <isc/string.h>
- #include <isc/util.h>
- static isc_once_t once = ISC_ONCE_INIT;
- static void
- initialize_rand(void)
- {
- #ifndef HAVE_ARC4RANDOM
- unsigned int pid = getpid();
- /*
- * The low bits of pid generally change faster.
- * Xor them with the high bits of time which change slowly.
- */
- pid = ((pid << 16) & 0xffff0000) | ((pid >> 16) & 0xffff);
- srand(time(NULL) ^ pid);
- #endif
- }
- static void
- initialize(void)
- {
- RUNTIME_CHECK(isc_once_do(&once, initialize_rand) == ISC_R_SUCCESS);
- }
- void
- isc_random_seed(isc_uint32_t seed)
- {
- initialize();
- #ifndef HAVE_ARC4RANDOM
- srand(seed);
- #else
- arc4random_addrandom((u_char *) &seed, sizeof(isc_uint32_t));
- #endif
- }
- void
- isc_random_get(isc_uint32_t *val)
- {
- REQUIRE(val != NULL);
- initialize();
- #ifndef HAVE_ARC4RANDOM
- /*
- * rand()'s lower bits are not random.
- * rand()'s upper bit is zero.
- */
- #if RAND_MAX >= 0xfffff
- /* We have at least 20 bits. Use lower 16 excluding lower most 4 */
- *val = ((rand() >> 4) & 0xffff) | ((rand() << 12) & 0xffff0000);
- #elif RAND_MAX >= 0x7fff
- /* We have at least 15 bits. Use lower 10/11 excluding lower most 4 */
- *val = ((rand() >> 4) & 0x000007ff) | ((rand() << 7) & 0x003ff800) |
- ((rand() << 18) & 0xffc00000);
- #else
- #error RAND_MAX is too small
- #endif
- #else
- *val = arc4random();
- #endif
- }
- isc_uint32_t
- isc_random_jitter(isc_uint32_t max, isc_uint32_t jitter) {
- isc_uint32_t rnd;
- REQUIRE(jitter < max || (jitter == 0 && max == 0));
- if (jitter == 0)
- return (max);
- isc_random_get(&rnd);
- return (max - rnd % jitter);
- }