.\" Copyright (c) 1993 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Paul Borman at Krystal Technologies.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"	@(#)rune.3	5.2 (Berkeley) 06/02/93
.\"
.Dd ""
.Dt RUNE 3
.Os
.Sh NAME
.Nm setrunelocale ,
.Nm setinvalidrune ,
.Nm sgetrune ,
.Nm sputrune
.Nd rune support for C
.Sh SYNOPSIS
.Fd #include <rune.h>
.Fd #include <errno.h>
.Ft int
.Fn setrunelocale "char *locale"
.Ft void
.Fn setinvalidrune "rune_t rune"
.Ft rune_t
.Fn sgetrune "const char *string" "size_t n" "char const **result"
.Ft int
.Fn sputrune "rune_t rune" "char *string" "size_t n" "char **result"
.Sh DESCRIPTION
The
.Fn setrunelocale
controls the type of encoding used to represent runes as multibyte strings
as well as the properties of the runes as defined in
\fB<ctype.h>\fP.
The
.Fa locale
argument indicates the locale which to load.
If the locale is successfully loaded,
.Dv 0
is returned, otherwise an errno value is returned to indicate the
type of error.
.Pp
The
.Fn setinvalidrune
function sets the value of the global value
.Ev _INVALID_RUNE
to be
.Fa rune.
.Pp
The
.Fn sgetrune
function tries to read a single multibyte character from
.Fa string ,
which is at most
.Fa n
bytes long.
If
.Fn sgetrune
is successful, the rune is returned.
If
.Fa result
is not
.Dv NULL ,
.Fa *result
will point to the first byte which was not converted in
.Fa string.
If the first
.Fa n
bytes of
.Fa string
do not describe a full multibyte character,
.Ev _INVALID_RUNE
is returned and
.Fa *result
will point to
.Fa string.
If there is an encoding error at the start of
.Fa string ,
.Ev _INVALID_RUNE
is returned and 
.Fa *result
will point to the second character of
.Fa string.
.Pp
the
.Fn sputrune
function tries to encode
.Fa rune
as a multibyte string and store it at
.Fa string ,
but no more than
.Fa n
bytes will be stored.
If
.Fa result
is not
.Dv NULL ,
.Fa *result
will be set to point to the first byte in string following the new
multibyte character.
If
.Fa string
is
.Dv NULL ,
.Fa *result
will point to
.Dv "(char *)0 +"
.Fa x ,
where
.Fa x
is the number of bytes that would be needed to store the multibyte value.
If the multibyte character would consist of more than
.Fa n
bytes and
.Fa result
is not
.Dv NULL ,
.Fa *result
will be set to
.Dv NULL.
In all cases, 
.Fn sputrune
will return the number of bytes which would be needed to store
.Fa rune
as a multibyte character.
.Sh RETURN VALUES
The
.Fn setrunelocale
function returns one of the following values:
.Bl -tag -width WWWWWWWW
.It Dv 0
.Fa setrunelocale was successful.
.It Ev EFAULT
.Fa locale
was
.Dv NULL .
.It Ev ENOENT
The locale could not be found.
.It Ev EFTYPE
The file found was not a valid file.
.It Ev EINVAL
The encoding indicated by the locale was unknown.
.El
.Pp
The
.Fn sgetrune
function either returns the rune read or
.Ev _INVALID_RUNE .
The
.Fn sputrune
function returns the number of bytes needed to store
.Fa rune
as a multibyte string.
.Sh FILES
.Bl -tag -width /usr/share/locale/locale/LC_CTYPE -compact
.It Pa $PATH_LOCALE/\fIlocale\fP/LC_CTYPE
.It Pa /usr/share/locale/\fIlocale\fP/LC_CTYPE
binary LC_CTYPE file for the locale \fIlocale\fP.
.El
.Sh "SEE ALSO
.Xr euc 4 ,
.Xr mbrune 3 ,
.Xr setlocale 3 ,
.Xr utf2 4
.Sh NOTE
The ANSI C type
.Ev wchar_t
is the same as
.Ev rune_t .
.Ev Rune_t
was chosen to accent the purposeful choice of not basing the
system with the ANSI C
primitives, which were, shall we say, less aesthetic.
.Sh HISTORY
These functions first appeared in
.Bx 4.4 .
.Pp
The
.Fn setrunelocale
function and the other non-ANSI rune functions were inspired by
.Nm Plan 9 from Bell Labs
as a much more sane alternative to the ANSI multibyte and
wide character support.
.\"They were conceived at the San Diego 1993 Summer USENIX conference by
.\"Paul Borman of Krystal Technologies, Keith Bostic of CSRG and Andrew Hume
.\"of Bell Labs.
.Pp
All of the ANSI multibyte and wide character
support functions are built using the rune functions.