freebsd-dev/lib/libc/uuid/uuid_compare.c
Xin LI 77fbf8f246 Avoid using intermediate variables by just comparing between
two values, the latter does not tend to have sign extension
and/or overflow bugs, and makes the code more obvious.

While I'm there, make use of a macro which is derived from
bin/ps/ps.c: ps_compat() to improve the readability of the
code.

Suggested by:	bde
MFC after:	1 week
2007-04-05 02:07:33 +00:00

77 lines
2.5 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>
/* A macro used to improve the readability of uuid_compare(). */
#define DIFF_RETURN(a, b, field) do { \
if ((a)->field != (b)->field) \
return (((a)->field < (b)->field) ? -1 : 1); \
} while (0)
/*
* 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;
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. */
DIFF_RETURN(a, b, time_low);
DIFF_RETURN(a, b, time_mid);
DIFF_RETURN(a, b, time_hi_and_version);
DIFF_RETURN(a, b, clock_seq_hi_and_reserved);
DIFF_RETURN(a, b, clock_seq_low);
res = memcmp(a->node, b->node, sizeof(a->node));
if (res)
return ((res < 0) ? -1 : 1);
return (0);
}
#undef DIFF_RETURN