.\"	$OpenBSD: wcslcpy.3,v 1.8 2024/08/07 04:59:45 guenther Exp $
.\"
.\" Copyright (c) 1998, 2000 Todd C. Miller <millert@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: August 7 2024 $
.Dt WCSLCPY 3
.Os
.Sh NAME
.Nm wcslcpy ,
.Nm wcslcat
.Nd size-bounded wide string copying and concatenation
.Sh SYNOPSIS
.In wchar.h
.Ft size_t
.Fn wcslcpy "wchar_t * restrict dst" "const wchar_t * restrict src" "size_t size"
.Ft size_t
.Fn wcslcat "wchar_t * restrict dst" "const wchar_t * restrict src" "size_t size"
.Sh DESCRIPTION
The
.Fn wcslcpy
and
.Fn wcslcat
functions copy and concatenate wide strings respectively.
They are designed to be safer, more consistent, and less error prone
replacements for
.Xr wcsncpy 3
and
.Xr wcsncat 3 .
Unlike those functions,
.Fn wcslcpy
and
.Fn wcslcat
take the full size of the buffer (not just the length) and guarantee to
terminate the result with a null wide character (as long as
.Fa size
is larger than 0 or, in the case of
.Fn wcslcat ,
as long as there is at least one wide character free in
.Fa dst ) .
Note that a wide character for the null wide character should be included in
.Fa size .
Also note that
.Fn wcslcpy
and
.Fn wcslcat
only operate on wide strings that are terminated with a null wide character
(L'\e0').
This means that for
.Fn wcslcpy
.Fa src
must be terminated with a null wide character and for
.Fn wcslcat
both
.Fa src
and
.Fa dst
must be terminated with a null wide character.
.Pp
The
.Fn wcslcpy
function copies up to
.Fa size
\(mi 1 wide characters from the wide string
.Fa src
to
.Fa dst ,
terminating the result with a null wide character.
.Pp
The
.Fn wcslcat
function appends the wide string
.Fa src
to the end of
.Fa dst .
It will append at most
.Fa size
\(mi wcslen(dst) \(mi 1 wide characters, terminating the result with a null
wide character.
.Pp
If the
.Fa src
and
.Fa dst
strings overlap, the behavior is undefined.
.Sh RETURN VALUES
The
.Fn wcslcpy
and
.Fn wcslcat
functions return the total length of the wide string they tried to create.
For
.Fn wcslcpy
that means the length of
.Fa src .
For
.Fn wcslcat
that means the initial length of
.Fa dst
plus
the length of
.Fa src .
While this may seem somewhat confusing, it was done to make
truncation detection simple.
.Pp
Note, however, that if
.Fn wcslcat
traverses
.Fa size
wide characters without finding a null wide character, the length of the
string is considered to be
.Fa size
and the destination wide string will not be terminated with a null wide
character (since there was no space for it).
This keeps
.Fn wcslcat
from running off the end of a wide string.
In practice this should not happen (as it means that either
.Fa size
is incorrect or that
.Fa dst
is not terminated with a null wide character).
The check exists to prevent potential security problems in incorrect code.
.Sh SEE ALSO
.Xr strlcpy 3 ,
.Xr swprintf 3 ,
.Xr wcsncat 3 ,
.Xr wcsncpy 3
.Sh STANDARDS
The
.Fn wcslcpy
and
.Fn wcslcat
functions conform to
.St -p1003.1-2024 .
.Sh HISTORY
The
.Fn wcslcpy
and
.Fn wcslcat
functions first appeared in
.Ox 3.8 .
.Sh AUTHORS
The
.Fn wcslcpy
and
.Fn wcslcat
functions are based on code by
.An Todd C. Miller Aq Mt millert@openbsd.org .