.\" $OpenBSD: mbstowcs.3,v 1.8 2015/10/24 23:07:41 mmcc Exp $
.\" $NetBSD: mbstowcs.3,v 1.6 2003/09/08 17:54:31 wiz Exp $
.\"
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.Dd $Mdocdate: October 24 2015 $
.Dt MBSTOWCS 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm mbstowcs
.Nd converts a multibyte character string to a wide-character string
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.In stdlib.h
.Ft size_t
.Fn mbstowcs "wchar_t * restrict pwcs" "const char * restrict s" "size_t n"
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
.Fn mbstowcs
converts a null-terminated multibyte character string pointed to by
.Fa s
to the corresponding wide-character string and stores up to
.Fa n
wide characters in the array pointed to by
.Fa pwcs .
Each character will be converted as if
.Xr mbtowc 3
is continuously called, except the internal state of
.Xr mbtowc 3
will not be affected.
.Pp
For state-dependent encoding,
.Fn mbstowcs
implies the multibyte character string pointed to by
.Fa s
always begin with an initial state.
.Pp
These are the special cases:
.Bl -tag -width 012345678901
.It pwcs == NULL
.Fn mbstowcs
returns the number of elements to store the whole wide-character string
corresponding to the multibyte character string pointed to by
.Fa s .
In this case,
.Fa n
is ignored.
.It s == NULL
Undefined (may cause the program to crash).
.El
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
.Fn mbstowcs
returns:
.Bl -tag -width 012345678901
.It 0 or positive
The value returned is the number of elements stored in the array pointed to by
.Fa pwcs ,
except for a terminating null wide character (if any).
If
.Fa pwcs
is not null and the value returned is equal to
.Fa n ,
the wide-character string pointed to by
.Fa pwcs
is not null terminated.
If
.Fa pwcs
is a null pointer, the value returned is the number of elements to contain
the whole string converted, except for a terminating null wide character.
.It (size_t)-1
The array indirectly pointed to by
.Fa s
contains a byte sequence forming invalid character.
In this case,
.Fn mbstowcs
sets
.Va errno
to indicate the error.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
.Fn mbstowcs
may cause an error in the following cases:
.Bl -tag -width Er
.It Bq Er EILSEQ
.Fa s
points to the string containing invalid or incomplete multibyte character.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr mbtowc 3 ,
.Xr setlocale 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn mbstowcs
function conforms to
.St -ansiC .
The restrict qualifier is added at
.\" .St -isoC99 .
ISO/IEC 9899/199
.Pq Dq ISO C99 .