libc/locale/mbsrtowcs.3

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.Dd August 7, 2020
.Dt MBSRTOWCS 3
.Os
.Sh NAME
.Nm mbsrtowcs ,
.Nm mbsnrtowcs
.Nd "convert a character string to a wide-character string (restartable)"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In wchar.h
.Ft size_t
.Fo mbsrtowcs
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t len"
.Fa "mbstate_t * restrict ps"
.Fc
.Ft size_t
.Fo mbsnrtowcs
.Fa "wchar_t * restrict dst" "const char ** restrict src" "size_t nms"
.Fa "size_t len" "mbstate_t * restrict ps"
.Fc
.Sh DESCRIPTION
The
.Fn mbsrtowcs
function converts a sequence of multibyte characters pointed to indirectly by
.Fa src
into a sequence of corresponding wide characters and stores at most
.Fa len
of them in the
.Vt wchar_t
array pointed to by
.Fa dst ,
until it encounters a terminating null character
.Pq Li '\e0' .
.Pp
If
.Fa dst
is
.Dv NULL ,
no characters are stored.
.Pp
If
.Fa dst
is not
.Dv NULL ,
the pointer pointed to by
.Fa src
is updated to point to the character after the one that conversion stopped at.
If conversion stops because a null character is encountered,
.Fa *src
is set to
.Dv NULL .
.Pp
The
.Vt mbstate_t
argument,
.Fa ps ,
is used to keep track of the shift state.
If it is
.Dv NULL ,
.Fn mbsrtowcs
uses an internal, static
.Vt mbstate_t
object, which is initialized to the initial conversion state
at program startup.
.Pp
The
.Fn mbsnrtowcs
function behaves identically to
.Fn mbsrtowcs ,
except that conversion stops after reading at most
.Fa nms
bytes from the buffer pointed to by
.Fa src .
.Sh RETURN VALUES
If successful, and
.Fa dst
is not NULL, the
.Fn mbsrtowcs
and
.Fn mbsnrtowcs
functions return the number of wide characters stored in
the array pointed to by
.Fa dst .
.Pp
If
.Fa dst
was NULL then the functions
.Fn mbsrtowcs
and
.Fn mbsnrtowcs
return the number of wide characters that would have been stored where
.Fa dst
points to an infinitely large array.
.Pp
If either one of the functions is not successful then
.Po Vt size_t Pc Ns \-1
is returned.
.Sh ERRORS
The
.Fn mbsrtowcs
and
.Fn mbsnrtowcs
functions will fail if:
.Bl -tag -width Er
.It Bq Er EILSEQ
An invalid multibyte character sequence was encountered.
.It Bq Er EINVAL
The conversion state is invalid.
.El
.Sh SEE ALSO
.Xr mbrtowc 3 ,
.Xr mbstowcs 3 ,
.Xr multibyte 3 ,
.Xr wcsrtombs 3
.Sh STANDARDS
The
.Fn mbsrtowcs
function conforms to
.St -isoC-99 .
.Pp
The
.Fn mbsnrtowcs
function is an extension to the standard.