ref: c90d38382860b13a7d6a804cb3db7e0ff9b8e0e1 dir: /sys/src/cmd/unix/drawterm/libc/runestrlen.c/
#include <u.h> #include <libc.h> long runestrlen(Rune *s) { return runestrchr(s, 0) - s; }