ref: c3399d1447d0c5e815c1262e0f99d69b6d4b3bfb dir: /sys/src/cmd/unix/drawterm/libc/runestrlen.c/
#include <u.h> #include <libc.h> long runestrlen(Rune *s) { return runestrchr(s, 0) - s; }