ref: a873aaf1f1f75fc9f9ed1975e0b7f6e1565c4efc dir: /sys/src/cmd/unix/drawterm/libc/runestrlen.c/
#include <u.h> #include <libc.h> long runestrlen(Rune *s) { return runestrchr(s, 0) - s; }