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freebsd-nq/share/man/man9/memcchr.9

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Introducing memcchr(3). It seems two of the file system drivers we have in the tree, namely ufs and ext3, use a function called `skpc()'. The meaning of this function does not seem to be documented in FreeBSD, but it turns out one needs to be a VAX programmer to understand what it does. SPKC is an instruction on the VAX that does the opposite of memchr(). It searches for the non-equal character. Add a new function called memcchr() to the tree that has the following advantages over skpc(): - It has a name that makes more sense than skpc(). Just like strcspn() matches the complement of strspn(), memcchr() is the complement of memchr(). - It is faster than skpc(). Similar to our strlen() in libc, it compares entire words, instead of single bytes. It seems that for this routine this yields a sixfold performance increase on amd64. - It has a man page.
2012-01-01 20:26:11 +00:00
.\" Copyright (c) 2012 Ed Schouten <ed@FreeBSD.org>
.\" 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
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.\" $FreeBSD$
.\"
.Dd January 1, 2012
.Dt MEMCCHR 9
.Os
.Sh NAME
.Nm memcchr
.Nd locate the complement of a byte in byte string
.Sh SYNOPSIS
.In sys/libkern.h
.Ft void *
.Fn memcchr "const void *b" "int c" "size_t len"
.Sh DESCRIPTION
The
.Fn memcchr
function locates the first occurrence of a byte unequal to
.Fa c
(converted to an
.Vt "unsigned char" )
in string
.Fa b .
.Sh RETURN VALUES
The
.Fn memcchr
Fix typo; return -> returns.
2012-01-01 20:30:48 +00:00
function returns a pointer to the byte located, or NULL if no such byte
Introducing memcchr(3). It seems two of the file system drivers we have in the tree, namely ufs and ext3, use a function called `skpc()'. The meaning of this function does not seem to be documented in FreeBSD, but it turns out one needs to be a VAX programmer to understand what it does. SPKC is an instruction on the VAX that does the opposite of memchr(). It searches for the non-equal character. Add a new function called memcchr() to the tree that has the following advantages over skpc(): - It has a name that makes more sense than skpc(). Just like strcspn() matches the complement of strspn(), memcchr() is the complement of memchr(). - It is faster than skpc(). Similar to our strlen() in libc, it compares entire words, instead of single bytes. It seems that for this routine this yields a sixfold performance increase on amd64. - It has a man page.
2012-01-01 20:26:11 +00:00
exists within
.Fa len
bytes.
.Sh SEE ALSO
.Xr memchr 3
.Sh HISTORY
The
.Fn memcchr
function first appeared in
.Fx 10.0 .
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