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5cc53d7965
The return value is not required to be the difference between the differing bytes, only less than zero, zero, or greater than zero. Reviewed by: fuz Event: Kitchener-Waterloo Hackathon 202406 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D47683
91 lines
2.9 KiB
Groff
91 lines
2.9 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd November 20, 2024
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.Dt MEMCMP 3
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.Os
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.Sh NAME
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.Nm memcmp
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.Nd compare bytes in memory
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In string.h
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.Ft int
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.Fn memcmp "const void *b1" "const void *b2" "size_t len"
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.Sh DESCRIPTION
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The
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.Fn memcmp
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function
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compares byte object
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.Fa b1
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against byte object
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.Fa b2 .
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Both objects are assumed to be
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.Fa len
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bytes long.
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.Sh RETURN VALUES
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The
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.Fn memcmp
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function returns zero if the two objects are identical.
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Zero-length objects are considered identical.
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The
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.Fn memcmp
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function returns a negative value if the first differing byte has a lower
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value in
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.Fa b1
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and a positive value if the first differing byte has a higher value in
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.Fa b1 .
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.Sh SEE ALSO
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.Xr bcmp 3 ,
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.Xr strcasecmp 3 ,
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.Xr strcmp 3 ,
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.Xr strcoll 3 ,
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.Xr strxfrm 3 ,
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.Xr timingsafe_memcmp 3 ,
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.Xr wmemcmp 3
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.Sh STANDARDS
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The
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.Fn memcmp
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function
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conforms to
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.St -isoC .
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.Sh CAVEATS
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If the objects differ, the C library
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.Fn memcmp
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implementation returns the difference between the first two differing bytes
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.Po treated as
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.Vt "unsigned char"
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values
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.Pc .
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This behavior is not specified by
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.St -isoC ,
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is not portable, and may not occur in light of compiler optimizations.
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