ref: 1d2767a6794afc7dfa1d6fb0f6dfa9e93f5c932d dir: /sys/src/cmd/unix/drawterm/libc/runestrlen.c/
#include <u.h> #include <libc.h> long runestrlen(Rune *s) { return runestrchr(s, 0) - s; }