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.Dd August 14, 2024 .Dt C32RTOMB 3 .Os """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh NAME .Nm c32rtomb .Nd Restartable UTF-32 code unit to multibyte conversion """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh LIBRARY .Lb libc """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh SYNOPSIS . n uchar.h . .Ft size_t .Fo c32rtomb .Fa "char * restrict s" .Fa "char32_t c32" .Fa "mbstate_t * restrict ps" .Fc """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh DESCRIPTION The .Nm function attempts to encode Unicode input as a multibyte character sequence output at .Fa s in the current locale, writing anywhere between zero and .Dv MB_CUR_MAX bytes, inclusive, to .Fa s , depending on the inputs and conversion state .Fa ps .
p The input .Fa c32 is a UTF-32 code unit, which represents a single Unicode scalar value, i.e., a Unicode code point that is not in the interval [0xd800,0xdfff] of surrogate code points.
p If a surrogate code point is passed, .Nm will return .Li (size_t)-1 to denote failure with .Xr errno 2 set to .Er EILSEQ .
p If .Fa ps is a null pointer, .Nm uses an internal .Vt mbstate_t object with static storage duration, distinct from all other .Vt mbstate_t objects
o including those used by .Xr mbrtoc16 3 , .Xr mbrtoc32 3 , and .Xr c16rtomb 3
c ,
which is initialized at program startup to the initial conversion
state.
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh RETURN VALUES
The
.Nm
function returns the number of bytes written to
.Fa s
on success, or sets
.Xr errno 2
and returns
.Li "(size_t)-1"
on failure.
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh EXAMPLES
Convert a sequence of Unicode scalar values to a multibyte sequence,
NUL-terminate it, and print it:
d -literal -offset indent char32_t c32[] = { 0x1f4a9, 0x20ac, 0x21 };
char buf[__arraycountb(c32)*MB_CUR_MAX + 1], *s = buf;
size_t i;
mbstate_t mbs = {0}; /* initial conversion state */
for (i = 0; i < __arraycount(c32); i++) {
size_t len;
len = c32rtomb(s, c32[i], &mbs);
if (len == (size_t)-1)
err(1, "c32rtomb");
assert(len < sizeof(buf) - (s - buf));
s += len;
}
*s = '\e0'; /* NUL-terminate */
printf("%s\en", buf);
.Ed
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh ERRORS
l -tag -width Bq t Bq Er EILSEQ A surrogate code point was passed as
.Fa c32 .
t Bq Er EILSEQ The Unicode scalar value requested cannot be encoded as a multibyte
sequence in the current locale.
t Bq Er EIO An error occurred in loading the locale's character conversions.
.El
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh SEE ALSO
.Xr c16rtomb 3 ,
.Xr mbrtoc16 3 ,
.Xr mbrtoc32 3 ,
.Xr uchar 3
.Rs
.%B The Unicode Standard
.%O Version 15.0 \(em Core Specification
.%Q The Unicode Consortium
.%D September 2022
.%U https://www.unicode.org/versions/Unicode15.0.0/UnicodeStandard-15.0.pdf
.Re
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh STANDARDS
The
.Nm
function conforms to
.St -isoC-2011 .
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh HISTORY
The
.Nm
function first appeared in
.Nx 11.0 .
Indexes created Sun Oct 12 09:09:55 GMT 2025