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/* Copyright (C) 2007 MySQL AB, Sergei Golubchik & Michael Widenius
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
/*
implements Universal Unique Identifiers (UUIDs), as in
DCE 1.1: Remote Procedure Call,
Open Group Technical Standard Document Number C706, October 1997,
(supersedes C309 DCE: Remote Procedure Call 8/1994,
which was basis for ISO/IEC 11578:1996 specification)
A UUID has the following structure:
Field NDR Data Type Octet # Note
time_low unsigned long 0-3 The low field of the
timestamp.
time_mid unsigned short 4-5 The middle field of
the timestamp.
time_hi_and_version unsigned short 6-7 The high field of the
timestamp multiplexed
with the version number.
clock_seq_hi_and_reserved unsigned small 8 The high field of the
clock sequence multi-
plexed with the variant.
clock_seq_low unsigned small 9 The low field of the
clock sequence.
node character 10-15 The spatially unique node
identifier.
*/
#include "mysys_priv.h"
#include <my_rnd.h>
#include <m_string.h>
#include <myisampack.h> /* mi_int2store, mi_int4store */
static my_bool my_uuid_inited= 0;
static struct my_rnd_struct uuid_rand;
static uint nanoseq;
static ulonglong uuid_time= 0;
static longlong interval_timer_offset;
static uchar uuid_suffix[2+6]; /* clock_seq and node */
static mysql_mutex_t LOCK_uuid_generator;
/*
Number of 100-nanosecond intervals between
1582-10-15 00:00:00.00 and 1970-01-01 00:00:00.00
*/
#define UUID_TIME_OFFSET ((ulonglong) 141427 * 24 * 60 * 60 * \
1000 * 1000 * 10)
#define UUID_VERSION 0x1000
#define UUID_VARIANT 0x8000
/* Helper function */
static void set_clock_seq()
{
uint16 clock_seq= ((uint)(my_rnd(&uuid_rand)*16383)) | UUID_VARIANT;
mi_int2store(uuid_suffix, clock_seq);
interval_timer_offset= (my_hrtime().val * 10 - my_interval_timer()/100 +
UUID_TIME_OFFSET);
}
/**
Init structures needed for my_uuid
@func my_uuid_init()
@param seed1 Seed for random generator
@param seed2 Seed for random generator
@note
Seed1 & seed2 should NOT depend on clock. This is to be able to
generate a random mac address according to UUID specs.
*/
void my_uuid_init(ulong seed1, ulong seed2)
{
uchar *mac= uuid_suffix+2;
ulonglong now;
if (my_uuid_inited)
return;
my_uuid_inited= 1;
now= my_interval_timer()/100 + interval_timer_offset;
nanoseq= 0;
if (my_gethwaddr(mac))
{
uint i;
/*
Generating random "hardware addr"
Specs explicitly specify that node identifier should NOT
correlate with a clock_seq value, so we use a separate
randominit() here.
*/
/* purecov: begin inspected */
my_rnd_init(&uuid_rand, (ulong) (seed2+ now/2), (ulong) (now+rand()));
for (i=0; i < array_elements(uuid_suffix) -2 ; i++)
mac[i]= (uchar)(my_rnd(&uuid_rand)*255);
/* purecov: end */
}
my_rnd_init(&uuid_rand, (ulong) (seed1 + now), (ulong) (now/2+ getpid()));
set_clock_seq();
mysql_mutex_init(key_LOCK_uuid_generator, &LOCK_uuid_generator, MY_MUTEX_INIT_FAST);
}
/**
Create a global unique identifier (uuid)
@func my_uuid()
@param to Store uuid here. Must be of size MY_UUID_SIZE (16)
*/
void my_uuid(uchar *to)
{
ulonglong tv;
uint32 time_low;
uint16 time_mid, time_hi_and_version;
DBUG_ASSERT(my_uuid_inited);
mysql_mutex_lock(&LOCK_uuid_generator);
tv= my_interval_timer()/100 + interval_timer_offset + nanoseq;
if (likely(tv > uuid_time))
{
/*
Current time is ahead of last timestamp, as it should be.
If we "borrowed time", give it back, just as long as we
stay ahead of the previous timestamp.
*/
if (nanoseq)
{
ulong delta;
DBUG_ASSERT((tv > uuid_time) && (nanoseq > 0));
/*
-1 so we won't make tv= uuid_time for nanoseq >= (tv - uuid_time)
*/
delta= MY_MIN(nanoseq, (ulong)(tv - uuid_time -1));
tv-= delta;
nanoseq-= delta;
}
}
else
{
if (unlikely(tv == uuid_time))
{
/*
For low-res system clocks. If several requests for UUIDs
end up on the same tick, we add a nano-second to make them
different.
( current_timestamp + nanoseq * calls_in_this_period )
may end up > next_timestamp; this is OK. Nonetheless, we'll
try to unwind nanoseq when we get a chance to.
If nanoseq overflows, we'll start over with a new numberspace
(so the if() below is needed so we can avoid the ++tv and thus
match the follow-up if() if nanoseq overflows!).
*/
if (likely(++nanoseq))
++tv;
}
if (unlikely(tv <= uuid_time))
{
/*
If the admin changes the system clock (or due to Daylight
Saving Time), the system clock may be turned *back* so we
go through a period once more for which we already gave out
UUIDs. To avoid duplicate UUIDs despite potentially identical
times, we make a new random component.
We also come here if the nanoseq "borrowing" overflows.
In either case, we throw away any nanoseq borrowing since it's
irrelevant in the new numberspace.
*/
set_clock_seq();
tv= my_interval_timer()/100 + interval_timer_offset;
nanoseq= 0;
DBUG_PRINT("uuid",("making new numberspace"));
}
}
uuid_time=tv;
mysql_mutex_unlock(&LOCK_uuid_generator);
time_low= (uint32) (tv & 0xFFFFFFFF);
time_mid= (uint16) ((tv >> 32) & 0xFFFF);
time_hi_and_version= (uint16) ((tv >> 48) | UUID_VERSION);
/*
Note, that the standard does NOT specify byte ordering in
multi-byte fields. it's implementation defined (but must be
the same for all fields).
We use big-endian, so we can use memcmp() to compare UUIDs
and for straightforward UUID to string conversion.
*/
mi_int4store(to, time_low);
mi_int2store(to+4, time_mid);
mi_int2store(to+6, time_hi_and_version);
bmove(to+8, uuid_suffix, sizeof(uuid_suffix));
}
void my_uuid_end()
{
if (my_uuid_inited)
{
my_uuid_inited= 0;
mysql_mutex_destroy(&LOCK_uuid_generator);
}
}
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