.\" $OpenBSD: mbsrtowcs.3,v 1.2 2007/05/31 19:19:29 jmc Exp $
.\" $NetBSD: mbsrtowcs.3,v 1.6 2003/09/08 17:54:31 wiz Exp $
.\"
.\" Copyright (c)2002 Citrus Project,
.\" All rights reserved.
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.Dd $Mdocdate: May 31 2007 $
.Dt MBSRTOWCS 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm mbsrtowcs
.Nd converts a multibyte character string to a wide character string \
(restartable)
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.Fd #include <wchar.h>
.Ft size_t
.Fn mbsrtowcs "wchar_t * restrict pwcs" "const char ** restrict s" "size_t n" \
"mbstate_t * restrict ps"
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
The
.Fn mbsrtowcs
converts the multibyte character string indirectly pointed to by
.Fa s
to the corresponding wide character string, and stores it in the
array pointed to by
.Fa pwcs .
The conversion stops due to the following reasons:
.Bl -bullet
.It
The conversion reaches a null byte.
In this case, the null byte is also converted.
.It
The
.Fn mbsrtowcs
has already stored
.Fa n
wide characters.
.It
The conversion encounters an invalid character.
.El
.Pp
Each character is converted as if
.Xr mbrtowc 3
is continuously called.
.Pp
After conversion,
if
.Fa pwcs
is not a
.Dv NULL
pointer,
the pointer object pointed to by
.Fa s
is a
.Dv NULL
pointer (if the conversion is stopped due to reaching a null byte)
or the first byte of the character just after the last character converted.
.Pp
If
.Fa pwcs
is not a
null pointer and the conversion is stopped due to reaching
a null byte, the
.Fn mbsrtowcs
places the state object pointed to by
.Fa ps
to an initial state after the conversion has taken place.
.Pp
The behaviour of the
.Fn mbsrtowcs
is affected by the
.Dv LC_CTYPE
category of the current locale.
.Pp
These are the special cases:
.Bl -tag -width 012345678901
.It "s == NULL || *s == NULL"
Undefined (may cause the program to crash).
.It "pwcs == NULL"
The conversion hass taken place, but the resultant wide character string
was discarded.
In this case, the pointer object pointed to by
.Fa s
is not modified and
.Fa n
is ignored.
.It "ps == NULL"
The
.Fn mbsrtowcs
uses its own internal state object to keep the conversion state,
instead of
.Fa ps
mentioned in this manual page.
.Pp
Calling any other functions in
.Em libc
never change the internal
state of
.Fn mbsrtowcs ,
which is initialized at startup time of the program.
.El
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
.Fn mbsrtowcs
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 mbsrtowcs
sets
.Va errno
to indicate the error.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
.Fn mbsrtowcs
may cause an error in the following cases:
.Bl -tag -width Er
.It Bq Er EILSEQ
The pointer pointed to by
.Fa s
points to an invalid or incomplete multibyte character.
.It Bq Er EINVAL
.Fa ps
points to an invalid or uninitialized mbstate_t object.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr mbrtowc 3 ,
.Xr mbstowcs 3 ,
.Xr setlocale 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn mbsrtowcs
function conforms to
.\" .St -isoC-amd1 .
ISO/IEC 9899/AMD1:1995
.Pq Dq ISO C90, Amendment 1 .
The restrict qualifier is added at
.\" .St -isoC99 .
ISO/IEC 9899/1999
.Dq Pq ISO C99 .