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.

1 files changed, 59 insertions, 0 deletions

diff --git a/share/man/man9/memcchr.3 b/share/man/man9/memcchr.3
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+++ b/share/man/man9/memcchr.3
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+.\" 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
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.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
+function return a pointer to the byte located, or NULL if no such byte
+exists within
+.Fa len
+bytes.
+.Sh SEE ALSO
+.Xr memchr 3
+.Sh HISTORY
+The
+.Fn memcchr
+function first appeared in
+.Fx 10.0 .