This is xnu-8019. See this file in:
/*
 * Copyright (c) 2004-2011 Apple Inc. All rights reserved.
 *
 * %Begin-Header%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 * %End-Header%
 */

#include <uuid/uuid.h>

#include <stdint.h>
#include <string.h>

#include <sys/random.h>
#include <sys/socket.h>
#include <sys/systm.h>
#include <sys/time.h>

extern int uuid_get_ethernet(u_int8_t *);

static void
read_node(uint8_t *node)
{
#if NETWORKING
	if (uuid_get_ethernet(node) == 0) {
		return;
	}
#endif /* NETWORKING */

	read_random(node, 6);
	node[0] |= 0x01;
}

static uint64_t
read_time(void)
{
	struct timespec tv;

	nanotime(&tv);

	return (tv.tv_sec * 10000000ULL) + (tv.tv_nsec / 100ULL) + 0x01B21DD213814000ULL;
}

void
uuid_clear(uuid_t uu)
{
	memset(uu, 0, sizeof(uuid_t));
}

int
uuid_compare(const uuid_t uu1, const uuid_t uu2)
{
	return memcmp(uu1, uu2, sizeof(uuid_t));
}

void
uuid_copy(uuid_t dst, const uuid_t src)
{
	memcpy(dst, src, sizeof(uuid_t));
}

static void
uuid_random_setflags(uuid_t out)
{
	out[6] = (out[6] & 0x0F) | 0x40;
	out[8] = (out[8] & 0x3F) | 0x80;
}

void
uuid_generate_random(uuid_t out)
{
	read_random(out, sizeof(uuid_t));
	uuid_random_setflags(out);
}

void
uuid_generate_early_random(uuid_t out)
{
	read_frandom(out, sizeof(uuid_t));
	uuid_random_setflags(out);
}

void
uuid_generate_time(uuid_t out)
{
	uint64_t time;

	read_node(&out[10]);
	read_random(&out[8], 2);

	time = read_time();
	out[0] = (uint8_t)(time >> 24);
	out[1] = (uint8_t)(time >> 16);
	out[2] = (uint8_t)(time >> 8);
	out[3] = (uint8_t)time;
	out[4] = (uint8_t)(time >> 40);
	out[5] = (uint8_t)(time >> 32);
	out[6] = (uint8_t)(time >> 56);
	out[7] = (uint8_t)(time >> 48);

	out[6] = (out[6] & 0x0F) | 0x10;
	out[8] = (out[8] & 0x3F) | 0x80;
}

void
uuid_generate(uuid_t out)
{
	uuid_generate_random(out);
}

int
uuid_is_null(const uuid_t uu)
{
	return !memcmp(uu, UUID_NULL, sizeof(uuid_t));
}

int
uuid_parse(const uuid_string_t in, uuid_t uu)
{
	int n = 0;

	sscanf(in,
	    "%2hhx%2hhx%2hhx%2hhx-"
	    "%2hhx%2hhx-"
	    "%2hhx%2hhx-"
	    "%2hhx%2hhx-"
	    "%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%n",
	    &uu[0], &uu[1], &uu[2], &uu[3],
	    &uu[4], &uu[5],
	    &uu[6], &uu[7],
	    &uu[8], &uu[9],
	    &uu[10], &uu[11], &uu[12], &uu[13], &uu[14], &uu[15], &n);

	return n != 36 || in[n] != '\0' ? -1 : 0;
}

void
uuid_unparse_lower(const uuid_t uu, uuid_string_t out)
{
	snprintf(out,
	    sizeof(uuid_string_t),
	    "%02x%02x%02x%02x-"
	    "%02x%02x-"
	    "%02x%02x-"
	    "%02x%02x-"
	    "%02x%02x%02x%02x%02x%02x",
	    uu[0], uu[1], uu[2], uu[3],
	    uu[4], uu[5],
	    uu[6], uu[7],
	    uu[8], uu[9],
	    uu[10], uu[11], uu[12], uu[13], uu[14], uu[15]);
}

void
uuid_unparse_upper(const uuid_t uu, uuid_string_t out)
{
	snprintf(out,
	    sizeof(uuid_string_t),
	    "%02X%02X%02X%02X-"
	    "%02X%02X-"
	    "%02X%02X-"
	    "%02X%02X-"
	    "%02X%02X%02X%02X%02X%02X",
	    uu[0], uu[1], uu[2], uu[3],
	    uu[4], uu[5],
	    uu[6], uu[7],
	    uu[8], uu[9],
	    uu[10], uu[11], uu[12], uu[13], uu[14], uu[15]);
}

void
uuid_unparse(const uuid_t uu, uuid_string_t out)
{
	uuid_unparse_upper(uu, out);
}