ref: d3da2e1b89f30f404c3d11053680098f1b7bf677
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;
}