NetBSD/lib/libc/locale/mbrlen.3

.\" $NetBSD: mbrlen.3,v 1.4 2003/04/16 13:34:40 wiz Exp $
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.Dd February 3, 2002
.Dt MBRLEN 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm mbrlen
.Nd get number of bytes consisting a multibyte character (restartable)
.\" ----------------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.In wchar.h
.Ft int
.Fn mbrlen "const char * restrict s" "size_t n" "mbstate_t * restrict ps"
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
The
.Fn mbrlen
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
.Fn mbrlen
is equivalent to the following call (except
.Fa ps
is evaluated only once):
.Pp
.Bd -literal
mbrtowc(NULL, s, n, (ps != NULL) ? ps : &internal);
.Ed
.Pp
Here,
.Fa internal
is an internal state object.
.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, these affect the conversion state object pointed by
.Fa ps ,
and the
.Fn mbrlen
treats the special sequence bytes
as if these are a part of the subsequent multibyte character.
.Pp
Unlike
.Xr mblen 3 ,
the
.Fn mbrlen
may accept the byte sequence being not complete character
but possible to consist a part of a valid character.
In this case, this function will accept the all such bytes
and save them into the conversion state object pointed by
.Fa ps .
They will be used at the subsequent call of this function to restart
the conversion suspended.
.Pp
The behaviour of the
.Fn mbrlen
is affected by LC_CTYPE category of the current locale.
.Pp
There are the special cases:
.Bl -tag -width 0123456789
.It "s == NULL"
The
.Fn mbrlen
sets the conversion state object pointed by
.Fa ps
to an initial state and always return 0.
Unlike
.Xr mblen 3 ,
the value returned does not indicate whether the current encoding of
the locale is state-dependent.
.Pp
In this case, the
.Fn mbrlen
ignores
.Fa n .
.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 mbrlen
always returns (size_t)-2.
.It "ps == NULL"
The
.Fn mbrlen
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 the
.Lb libc
never change the internal
state of the
.Fn mbrlen ,
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.
This internal state is initialized at startup time of the program.
.El
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
The
.Fn mbrlen
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 "(size_t)-2"
.Fa s
points the byte sequence which is possible to consist a part of valid
multibyte character but incomplete.
When
.Fa n
is at least MB_CUR_MAX,
this case can only occur if the array pointed
.Fa s
contains redundant shift sequence.
.It "(size_t)-1"
.Fa s
points a illegal byte sequence which does not form a valid multibyte
character.
In this case, the
.Fn mbrtowc
sets errno to indicate the error.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
The
.Fn mbrlen
may causes an error in the following case:
.Bl -tag -width Er
.It Bq Er EILSEQ
.Fa s
points an invalid multibyte character.
.It Bq Er EINVAL
.Fa ps
points an invalid or uninitialized mbstate_t object.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr mblen 3 ,
.Xr mbrtowc 3 ,
.Xr setlocale 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn mbrlen
function conforms to
.St -isoC-amd1 .
The restrict qualifier is added at
.St -isoC99 .