ref: c97d16f7a91d4eb7f6e8a9014079a7d6759bc33c
dir: /sys/src/ape/lib/ap/plan9/9readn.c/
#include "sys9.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;
}