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