.Dd March 10 2024
.Dt U8LEN 3
.Os
.Sh NAME
.Nm u8len
.Nd count Unicode codepoints
.Sh LIBRARY
.Lb mlib
.Sh SYNOPSIS
.In mbstring.h
.Ft size_t
.Fn u8len "const char8_t *s" "size_t n"
.Sh DESCRIPTION
The
.Fn u8len
function returns the number of UTF-8 encoded Unicode codepoints in the
buffer
.Fa s
of length
.Fa n
bytes.
.Pp
Invalid bytes are interpreted as having a length of 1 byte.
.Sh RETURN VALUES
The
.Fn u8len
function returns the number of codepoints in the buffer
.Fa s .
.Sh EXAMPLES
The following call to
.Fn u8len
will return 17 while the call to
.Fn strlen
will return 22 as a result of use of multibyte-characters in
.Fa s .
.Bd -literal -offset indent
struct u8view sv = U8V(u8\(dq„Der Große Duden“\(dq);
size_t blen = strlen((char *)sv.p);
size_t cplen = u8len(U8_ARGS(sv));
.Ed
.Sh SEE ALSO
.Xr u8glen 3 ,
.Xr U8V 3 ,
.Xr unicode 7 ,
.Xr utf\-8 7
.Sh STANDARDS
.Rs
.%A F. Yergeau
.%D November 2003
.%R RFC 3629
.%T UTF-8, a transformation format of ISO 10646
.Re
.Sh AUTHORS
.An Thomas Voss Aq Mt mail@thomasvoss.com
.Sh CAVEATS
The return value of
.Fn u8len
does not necessarily represent the number of human-preceived characters
in the given buffer;
multiple codepoints may combine to form one human-preceived character
that spans a single column.
To count user-preceived codepoints
.Pq also known as graphemes ,
you may want to use the
.Xr u8glen 3
function.