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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: }