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#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
static struct
{
QLock;
Rendez producer;
Rendez consumer;
ulong randomcount;
uchar buf[1024];
uchar *ep;
uchar *rp;
uchar *wp;
uchar next;
uchar bits;
uchar wakeme;
uchar filled;
int target;
int kprocstarted;
ulong randn;
} rb;
static int
rbnotfull(void*)
{
int i;
i = rb.wp - rb.rp;
if(i < 0)
i += sizeof(rb.buf);
return i < rb.target;
}
static int
rbnotempty(void*)
{
return rb.wp != rb.rp;
}
static void
genrandom(void*)
{
setpri(PriBackground);
for(;;) {
for(;;)
if(++rb.randomcount > 100000)
break;
if(anyhigher())
sched();
if(!rbnotfull(0))
sleep(&rb.producer, rbnotfull, 0);
}
}
/*
* produce random bits in a circular buffer
*/
static void
randomclock(void)
{
uchar *p;
if(rb.randomcount == 0)
return;
if(!rbnotfull(0)) {
rb.filled = 1;
return;
}
rb.bits = (rb.bits<<2) ^ (rb.randomcount&3);
rb.randomcount = 0;
rb.next += 2;
if(rb.next != 8)
return;
rb.next = 0;
*rb.wp ^= rb.bits ^ *rb.rp;
p = rb.wp+1;
if(p == rb.ep)
p = rb.buf;
rb.wp = p;
if(rb.wakeme)
wakeup(&rb.consumer);
}
void
randominit(void)
{
/* Frequency close but not equal to HZ */
addclock0link(randomclock, 13);
rb.target = 16;
rb.ep = rb.buf + sizeof(rb.buf);
rb.rp = rb.wp = rb.buf;
}
/*
* consume random bytes from a circular buffer
*/
ulong
randomread(void *xp, ulong n)
{
int i, sofar;
uchar *e, *p;
p = xp;
qlock(&rb);
if(waserror()){
qunlock(&rb);
nexterror();
}
if(!rb.kprocstarted){
rb.kprocstarted = 1;
kproc("genrand", genrandom, nil, 0);
}
for(sofar = 0; sofar < n; sofar += i){
i = rb.wp - rb.rp;
if(i == 0){
rb.wakeme = 1;
wakeup(&rb.producer);
sleep(&rb.consumer, rbnotempty, 0);
rb.wakeme = 0;
continue;
}
if(i < 0)
i = rb.ep - rb.rp;
if((i+sofar) > n)
i = n - sofar;
memmove(p + sofar, rb.rp, i);
e = rb.rp + i;
if(e == rb.ep)
e = rb.buf;
rb.rp = e;
}
if(rb.filled && rb.wp == rb.rp){
i = 2*rb.target;
if(i > sizeof(rb.buf) - 1)
i = sizeof(rb.buf) - 1;
rb.target = i;
rb.filled = 0;
}
poperror();
qunlock(&rb);
wakeup(&rb.producer);
return n;
}
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