ref: f5cc6fbe3a7bcf8bdb002c646ddd519014afafd2
dir: /lib9/readn.c/
#include "lib9.h" long readn(int f, void *av, long n) { char *a; long m, t; a = av; t = 0; while(t < n){ m = read(f, a+t, n-t); if(m <= 0){ if(t == 0) return m; break; } t += m; } return t; }