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freebsd/lib/libc/uuid/uuid_compare.c
Xin LI da4ab3aa26 In DCE 1.1, the time_low value is defined as an unsigned 32-bit
integer.  Presently, our implementation employs an approach that
converts the value to int64_t, then back to int, unfortunately,
this approach can be problematic when the the difference between
the two time_low is larger than 0x7fffffff, as the value is then
truncated to int.

To quote the test case from the original PR, the following is
true with the current implementation:

865e1a56-b9d9-11d9-ba27-0003476f2e88 < 062ac45c-b9d9-11d9-ba27-0003476f2e88

However, according to the DCE specification, the expected result
should be:

865e1a56-b9d9-11d9-ba27-0003476f2e88 > 062ac45c-b9d9-11d9-ba27-0003476f2e88

This commit adds a new intermediate variable which uses int64_t
to store the result of subtraction between the two time_low values,
which would not introduce different semantic of the MSB found in
time_low value.

PR:		83107
Submitted by:	Steve Sears <sjs at acm dot org>
MFC After:	1 month
2006-08-03 03:34:36 +00:00

89 lines
2.9 KiB
C

/*-
* Copyright (c) 2002,2005 Marcel Moolenaar
* Copyright (c) 2002 Hiten Mahesh Pandya
* All rights reserved.
*
* 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, this list of conditions and the following disclaimer.
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS 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 ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <string.h>
#include <uuid.h>
/*
* uuid_compare() - compare two UUIDs.
* See also:
* http://www.opengroup.org/onlinepubs/009629399/uuid_compare.htm
*
* NOTE: Either UUID can be NULL, meaning a nil UUID. nil UUIDs are smaller
* than any non-nil UUID.
*/
int32_t
uuid_compare(const uuid_t *a, const uuid_t *b, uint32_t *status)
{
int res;
int64_t res64;
if (status != NULL)
*status = uuid_s_ok;
/* Deal with NULL or equal pointers. */
if (a == b)
return (0);
if (a == NULL)
return ((uuid_is_nil(b, NULL)) ? 0 : -1);
if (b == NULL)
return ((uuid_is_nil(a, NULL)) ? 0 : 1);
/*
* We have to compare the hard way.
*
* Note that time_low is defined as unsigned 32-bit
* integer, therefore, with a significantly large
* a->time_low and a small b->time_low, we will end
* up with a value which is larger than 0x7fffffff
* which is negative if casted to signed 32-bit
* integer.
*/
res64 = (int64_t)a->time_low - (int64_t)b->time_low;
if (res64)
return ((res64 < 0) ? -1 : 1);
res = (int)a->time_mid - (int)b->time_mid;
if (res)
return ((res < 0) ? -1 : 1);
res = (int)a->time_hi_and_version - (int)b->time_hi_and_version;
if (res)
return ((res < 0) ? -1 : 1);
res = (int)a->clock_seq_hi_and_reserved -
(int)b->clock_seq_hi_and_reserved;
if (res)
return ((res < 0) ? -1 : 1);
res = (int)a->clock_seq_low - (int)b->clock_seq_low;
if (res)
return ((res < 0) ? -1 : 1);
res = memcmp(a->node, b->node, sizeof(a->node));
if (res)
return ((res < 0) ? -1 : 1);
return (0);
}