xref: /netbsd-src/lib/libc/locale/wcsrtombs.3 (revision 67741c36810810c6763155043aea2dad579d6abe)

.\" $NetBSD: wcsrtombs.3,v 1.18 2024/10/13 14:56:30 rillig Exp $
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.Dd October 13, 2024
.Dt WCSRTOMBS 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm wcsrtombs ,
.Nm wcsnrtombs
.Nd converts a wide-character string to a multibyte character string \
(restartable)
.\" ----------------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.
.In wchar.h
.
.Ft size_t
.Fo wcsrtombs
.Fa "char * restrict s"
.Fa "const wchar_t ** restrict pwcs"
.Fa "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.
.Ft size_t
.Fo wcsnrtombs
.Fa "char * restrict s"
.Fa "const wchar_t ** restrict pwcs"
.Fa "size_t nwc"
.Fa "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
The
.Fn wcsrtombs
function converts the NUL-terminated wide-character string indirectly
pointed to by
.Fa pwcs
to the corresponding multibyte character string,
and stores it in the array pointed to by
.Fa s .
The conversion stops due to the following reasons:
.Bl -bullet
.It
The conversion reaches a NUL wide character.
In this case, the NUL wide character is also converted.
.It
The
.Fn wcsrtombs
has already stored
.Fa n
bytes in the array pointed to by
.Fa s .
.It
The conversion encounters an invalid character.
.El
.Pp
Each character will be converted as if
.Xr wcrtomb 3
is continuously called, except the internal state of
.Xr wcrtomb 3
will not be affected.
.Pp
After conversion,
if
.Fa s
is not a NULL pointer, the pointer object pointed to by
.Fa pwcs
is a NULL pointer
.Pq if the conversion is stopped due to reaching a NUL wide character
or points to the first byte of the character just after the last
character converted.
.Pp
If
.Fa s
is not a NULL pointer and the conversion is stopped due to reaching
a NUL wide character,
.Fn wcsrtombs
places the state object pointed to by
.Fa ps
to an initial state after the conversion is taken place.
.Pp
The behavior of
.Fn wcsrtombs
is affected by the
.Dv LC_CTYPE
category of the current locale.
.Pp
These are the special cases:
.Bl -tag -width Li
.It Li "s == NULL"
.Fn wcsrtombs
returns the number of bytes to store the whole multibyte character string
corresponding to the wide-character string pointed to by
.Fa pwcs ,
not including the terminating NUL byte.
In this case,
.Fa n
is ignored.
.It Li "pwcs == NULL || *pwcs == NULL"
Undefined (may cause the program to crash).
.It Li "ps == NULL"
.Fn wcsrtombs
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
.Lb libc
never changes the internal
state of
.Fn wcsrtombs ,
which is initialized at startup time of the program.
.El
.Pp
The
.Fn wcsnrtombs
function behaves identically to
.Fn wcsrtombs ,
except that the conversion stops after reading at most
.Fa nwc
characters from the buffer pointed to by
.Fa pwcs .
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
The
.Fn wcsrtombs
and
.Fn wcsnrtombs
functions return:
.Bl -tag -width Li
.It Li 0 , No or positive
Number of bytes stored in the array pointed to by
.Fa s ,
except for a NUL byte.
There are no cases that the value returned is greater than
.Fa n
.Po
unless
.Fa s
is a NULL pointer
.Pc .
If the return value is equal to
.Fa n ,
the string pointed to by
.Fa s
will not be NUL-terminated.
.It Li "(size_t)-1"
.Fa pwcs
points to a string containing an invalid wide character.
The
.Fn wcsrtombs
also sets
.Va errno
to indicate the error.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
The
.Fn wcsrtombs
and
.Fn wcsnrtombs
functions may fail with the following errors:
.Bl -tag -width Er
.It Bq Er EILSEQ
.Fa pwcs
points to a string containing an invalid wide character.
.It Bq Er EINVAL
.Fa ps
points to an invalid or uninitialized
.Vt mbstate_t
object.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr setlocale 3 ,
.Xr wcrtomb 3 ,
.Xr wcstombs 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn wcsrtombs
function conforms to
.St -ansiC .
The
.Li restrict
qualifier was added by
.St -isoC-99 .
.Pp
The
.Fn wcsnrtombs
function conforms to
.St -p1003.1-2008 .