ref: ceed9b8853ab7b10e5a9e39704e712bfce53ce8a
dir: /sys/src/libc/fmt/runevsnprint.c/
#include <u.h>
#include <libc.h>
int
runevsnprint(Rune *buf, int len, char *fmt, va_list args)
{
Fmt f;
if(len <= 0)
return -1;
f.runes = 1;
f.start = buf;
f.to = buf;
f.stop = buf + len - 1;
f.flush = nil;
f.farg = nil;
f.nfmt = 0;
f.args = args;
dofmt(&f, fmt);
*(Rune*)f.to = '\0';
return (Rune*)f.to - buf;
}