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Annotation of embedaddon/ntp/lib/isc/random.c, revision 1.1.1.1

1.1       misho       1: /*
                      2:  * Copyright (C) 2004, 2005, 2007  Internet Systems Consortium, Inc. ("ISC")
                      3:  * Copyright (C) 1999-2003  Internet Software Consortium.
                      4:  *
                      5:  * Permission to use, copy, modify, and/or 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.
                      8:  *
                      9:  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
                     10:  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
                     11:  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
                     12:  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
                     13:  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
                     14:  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
                     15:  * PERFORMANCE OF THIS SOFTWARE.
                     16:  */
                     17: 
                     18: /* $Id: random.c,v 1.25 2007/06/19 23:47:17 tbox Exp $ */
                     19: 
                     20: /*! \file */
                     21: 
                     22: #include <config.h>
                     23: 
                     24: #include <stdlib.h>
                     25: #include <time.h>              /* Required for time(). */
                     26: #ifdef HAVE_SYS_TYPES_H
                     27: #include <sys/types.h>
                     28: #endif
                     29: #ifdef HAVE_UNISTD_H
                     30: #include <unistd.h>
                     31: #endif
                     32: 
                     33: #include <isc/mutex.h>
                     34: #include <isc/once.h>
                     35: #include <isc/random.h>
                     36: #include <isc/string.h>
                     37: #include <isc/util.h>
                     38: 
                     39: static isc_once_t once = ISC_ONCE_INIT;
                     40: 
                     41: static void
                     42: initialize_rand(void)
                     43: {
                     44: #ifndef HAVE_ARC4RANDOM
                     45:        unsigned int pid = getpid();
                     46:        
                     47:        /*
                     48:         * The low bits of pid generally change faster.
                     49:         * Xor them with the high bits of time which change slowly.
                     50:         */
                     51:        pid = ((pid << 16) & 0xffff0000) | ((pid >> 16) & 0xffff);
                     52: 
                     53:        srand(time(NULL) ^ pid);
                     54: #endif
                     55: }
                     56: 
                     57: static void
                     58: initialize(void)
                     59: {
                     60:        RUNTIME_CHECK(isc_once_do(&once, initialize_rand) == ISC_R_SUCCESS);
                     61: }
                     62: 
                     63: void
                     64: isc_random_seed(isc_uint32_t seed)
                     65: {
                     66:        initialize();
                     67: 
                     68: #ifndef HAVE_ARC4RANDOM
                     69:        srand(seed);
                     70: #else
                     71:        arc4random_addrandom((u_char *) &seed, sizeof(isc_uint32_t));
                     72: #endif
                     73: }
                     74: 
                     75: void
                     76: isc_random_get(isc_uint32_t *val)
                     77: {
                     78:        REQUIRE(val != NULL);
                     79: 
                     80:        initialize();
                     81: 
                     82: #ifndef HAVE_ARC4RANDOM
                     83:        /*
                     84:         * rand()'s lower bits are not random.
                     85:         * rand()'s upper bit is zero.
                     86:         */
                     87:        *val = ((rand() >> 4) & 0xffff) | ((rand() << 12) & 0xffff0000);
                     88: #else
                     89:        *val = arc4random();
                     90: #endif
                     91: }
                     92: 
                     93: isc_uint32_t
                     94: isc_random_jitter(isc_uint32_t max, isc_uint32_t jitter) {
                     95:        REQUIRE(jitter < max);
                     96:        if (jitter == 0)
                     97:                return (max);
                     98:        else
                     99: #ifndef HAVE_ARC4RANDOM
                    100:                return (max - rand() % jitter);
                    101: #else
                    102:                return (max - arc4random() % jitter);
                    103: #endif
                    104: }