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.Dd $Mdocdate: April 23 2018 $
.Dt MEMCMP 9
.Os
.Sh NAME
.Nm skpc ,
.Nm scanc ,
.Nm bcmp ,
.Nm timingsafe_bcmp ,
.Nm memchr ,
.Nm memcmp
.Nd kernel library byte string routines
.Sh SYNOPSIS
.In lib/libkern/libkern.h
.Ft int
.Fn skpc "int mask" "size_t size" "u_char *cp"
.Ft int
.Fn scanc "u_int size" "const u_char *cp" "const u_char *table" "int mask"
.Ft int
.Fn bcmp "const void *b1" "const void *b2" "size_t len"
.Ft int
.Fn timingsafe_bcmp "const void *b1" "const void *b2" "size_t len"
.Ft void *
.Fn memchr "const void *b" "int c" "size_t len"
.Ft int
.Fn memcmp "const void *b1" "const void *b2" "size_t len"
.Sh DESCRIPTION
The
.Fn skpc
function locates the first unsigned character of value different than
.Fa mask
inside the string
.Fa cp .
.Pp
The
.Fn scanc
function expects a string of indexes into the table
.Fa table .
Each table element is bitwise ANDed against
.Fa mask .
.Pp
.Fn skpc
and
.Fn scanc
expect the string to be of size
.Fa size ,
and return the index relative to the end of the string where the match
occurred, or zero if
.Fa mask
is not present in the string.
.Pp
The remaining functions have the same semantics as their libc counterparts,
.Xr bcmp 3 ,
.Xr timingsafe_bcmp 3 ,
.Xr memchr 3 ,
and
.Xr memcmp 3 .
.Sh STANDARDS
The
.Fn memchr
and
.Fn memcmp
functions conform to
.St -ansiC .
.Sh HISTORY
The
.Fn skpc
and
.Fn scanc
functions are based on vax instructions of the same name.