NetBSD/lib/libc/locale/mblen.3

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.\" $NetBSD: mblen.3,v 1.2 2002/03/18 07:56:28 wiz Exp $
.\"
.\" Copyright (c)2002 Citrus Project,
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
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.Dd February 3, 2002
.Dt MBLEN 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm mblen
.Nd get number of bytes consisting a multibyte character
.\" ----------------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.Fd #include \*[Lt]stdlib.h\*[Gt]
.Ft int
.Fn mblen "const char *s" "size_t n"
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
The
.Fn mblen
function usually determines the number of bytes consisting in
a multibyte character pointed by
.Fa s
and return it.
This function shall only examine max n bytes of the array beginning from
.Fa s .
.Pp
In state-dependent encodings,
.Fa s
may point the special sequence bytes to change the shift-state.
Although such sequence bytes corresponds to no individual
wide-character code,
the
.Fn mblen
changes the own state by them and treats them
as if they are a part of the subsequence multibyte character.
.Pp
Unlike
.Xr mbrlen 3 ,
the first
.Fa n
bytes pointed by
.Fa s
need to form an entire multibyte character.
Otherwise, this function causes an error.
.Pp
.Fn mblen
is equivalent to the following call, except the internal state of the
.Xr mbtowc 3
function is not affected:
.Pp
.Bd -literal
mbtowc(NULL, s, n);
.Ed
.Pp
Calling any other functions in the
.Lb libc
never change the internal
state of the
.Fn mblen ,
except for calling
.Xr setlocale 3
with changing LC_CTYPE category of the current locale.
Such
.Xr setlocale 3
call causes the internal state of this function to be indeterminate.
.Pp
The behaviour of the
.Fn mblen
is affected by LC_CTYPE category of the current locale.
.Pp
There are special cases:
.Bl -tag -width 0123456789
.It "s == NULL"
The
.Fn mblen
initializes its own internal state to an initial state, and
determines whether the current encoding is state-dependent.
This function returns 0 if the encoding is state-independent,
otherwise non-zero.
.It "n == 0"
In this case,
the first
.Fa n
bytes of the array pointed by
.Fa s
never form a complete character. Thus, the
.Fn mblen
always fails.
.El
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
In the usual cases, the
.Fn mblen
returns:
.Bl -tag -width 0123456789
.It "0"
.Fa s
points a null byte (\'\\0\').
.It "positive"
The value returned is
a number of bytes for the valid multibyte character pointed by
.Fa s .
There is no cases that this value is greater than
.Fa n
or the value of MB_CUR_MAX macro.
.It "-1"
.Fa s
points an invalid or incomplete multibyte character.
The
.Fn mblen
also sets errno to indicate the error.
.El
.Pp
In the case that
.Fa s
is equal to NULL, the
.Fn mblen
returns:
.Bl -tag -width 0123456789
.It "0"
The current encoding is state-independent.
.It "non-zero"
The current encoding is state-dependent.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
The
.Fn mblen
may causes an error in the following case:
.Bl -tag -width Er
.It Bq Er EILSEQ
.Fa s
points an invalid or incomplete multibyte character.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr mbrlen 3 ,
.Xr mbtowc 3 ,
.Xr setlocale 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn mblen
function conforms to
.St -ansiC .