.\" Copyright (c) 2002-2004 Tim J. Robbins
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.\" $FreeBSD: head/lib/libc/locale/mbsrtowcs.3 140081 2005-01-11 20:50:51Z ru $
.\"
.Dd December 26, 2013
.Dt MBSRTOWCS 3
.Os
.Sh NAME
.Nm mbsrtowcs ,
.Nm mbsrtowcs_l ,
.Nm mbsnrtowcs ,
.Nm mbsnrtowcs_l
.Nd "convert a character string to a wide-character string (restartable)"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In wchar.h
.Ft size_t
.Fo mbsrtowcs
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t len"
.Fa "mbstate_t * restrict ps"
.Fc
.Ft size_t
.Fo mbsnrtowcs
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t nms"
.Fa "size_t len" "mbstate_t * restrict ps"
.Fc
.In xlocale.h
.Ft size_t
.Fo mbsrtowcs_l
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t len"
.Fa "mbstate_t * restrict ps" "locale_t locale"
.Fc
.Ft size_t
.Fo mbsnrtowcs_l
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t nms"
.Fa "size_t len" "mbstate_t * restrict ps" "locale_t locale"
.Fc
.Sh DESCRIPTION
The
.Fn mbsrtowcs
and
.Fn mbsrtowcs_l
functions convert a sequence of multibyte characters pointed to indirectly by
.Fa src
into a sequence of corresponding wide characters and store at most
.Fa len
of them in the
.Vt wchar_t
array pointed to by
.Fa dst ,
until they encounter a terminating null character
.Pq Li '\e0' .
.Pp
If
.Fa dst
is
.Dv NULL ,
no characters are stored.
.Pp
If
.Fa dst
is not
.Dv NULL ,
the pointer pointed to by
.Fa src
is updated to point to the character after the one that conversion stopped at.
If conversion stops because a null character is encountered,
.Fa *src
is set to
.Dv NULL .
.Pp
The
.Vt mbstate_t
argument,
.Fa ps ,
is used to keep track of the shift state.
If it is
.Dv NULL ,
.Fn mbsrtowcs
and
.Fn mbsrtowcs_l
use an internal, static
.Vt mbstate_t
object, which is initialized to the initial conversion state
at program startup.
.Pp
The
.Fn mbsnrtowcs
and
.Fn mbsnrtowcs_l
functions behave identically to
.Fn mbsrtowcs
and
.Fn mbsrtowcs_l ,
except that conversion stops after reading at most
.Fa nms
bytes from the buffer pointed to by
.Fa src .
.Pp
The
.Fn mbsrtowcs_l
and
.Fn mbsnrtowcs_l
functions take an explicit
.Fa locale
argument, whereas the
.Fn mbsrtowcs
and
.Fn mbsnrtowcs
functions use the current global or per-thread locale.
.Sh RETURN VALUES
The
.Fn mbsrtowcs ,
.Fn mbsrtowcs_l ,
.Fn mbsnrtowcs ,
and
.Fn mbsnrtowcs_l
functions return the number of wide characters stored in
the array pointed to by
.Fa dst
if successful, otherwise they return
.Po Vt size_t Pc Ns \-1 .
.Sh ERRORS
The
.Fn mbsrtowcs ,
.Fn mbsrtowcs_l ,
.Fn mbsnrtowcs ,
and
.Fn mbsnrtowcs_l
functions will fail if:
.Bl -tag -width Er
.It Bq Er EILSEQ
An invalid multibyte character sequence was encountered.
.It Bq Er EINVAL
The conversion state is invalid.
.El
.Sh SEE ALSO
.Xr mbrtowc 3 ,
.Xr mbstowcs 3 ,
.Xr multibyte 3 ,
.Xr wcsrtombs 3 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn mbsrtowcs
function conforms to
.St -isoC-99 .
.Pp
The
.Fn mbsrtowcs_l ,
.Fn mbsnrtowcs ,
and
.Fn mbsnrtowcs_l
functions are an extension to the standard.