#include	"dat.h"#include	"fns.h" static struct{	QLock	l;	Rendez	producer;	Rendez	consumer;	Rendez	clock;	ulong	randomcount;	uchar	buf[1024];	uchar	*ep;	uchar	*rp;	uchar	*wp;	uchar	next;	uchar	bits;	uchar	wakeme;	uchar	filled;	int	kprocstarted;	ulong	randn;	int	target;} rb; static intrbnotfull(void *v){	int i; 	USED(v);	i = rb.wp - rb.rp;	if(i < 0)		i += sizeof(rb.buf);	return i < rb.target;} static intrbnotempty(void *v){	USED(v);	return rb.wp != rb.rp;} /* *  spin counting up */static voidgenrandom(void *v){	USED(v);	oslopri();	for(;;){		for(;;)			if(++rb.randomcount > 65535)				break;		if(rb.filled || !rbnotfull(0))			Sleep(&rb.producer, rbnotfull, 0);	}} /* *  produce random bits in a circular buffer */static voidrandomclock(void *v){	uchar *p; 	USED(v);	for(;; osmillisleep(20)){		while(!rbnotfull(0)){			rb.filled = 1;			Sleep(&rb.clock, rbnotfull, 0);		}		if(rb.randomcount == 0)			continue; 		rb.bits = (rb.bits<<2) ^ rb.randomcount;		rb.randomcount = 0; 		rb.next++;		if(rb.next != 8/2)			continue;		rb.next = 0; 		p = rb.wp;		*p ^= rb.bits;		if(++p == rb.ep)			p = rb.buf;		rb.wp = p; 		if(rb.wakeme)			Wakeup(&rb.consumer);	}} voidrandominit(void){	rb.target = 16;	rb.ep = rb.buf + sizeof(rb.buf);	rb.rp = rb.wp = rb.buf;} /* *  consume random bytes from a circular buffer */ulongrandomread(void *xp, ulong n){	uchar *e, *p, *r;	ulong x;	int i; 	p = xp; if(0)print("A%ld.%d.%lux|", n, rb.target, getcallerpc(&xp));	if(waserror()){		qunlock(&rb.l);		nexterror();	} 	qlock(&rb.l);	if(!rb.kprocstarted){		rb.kprocstarted = 1;		kproc("genrand", genrandom, 0, 0);		kproc("randomclock", randomclock, 0, 0);	} 	for(e = p + n; p < e; ){		r = rb.rp;		if(r == rb.wp){			rb.wakeme = 1;			Wakeup(&rb.clock);			Wakeup(&rb.producer);			Sleep(&rb.consumer, rbnotempty, 0);			rb.wakeme = 0;			continue;		} 		/*		 *  beating clocks will be predictable if		 *  they are synchronized.  Use a cheap pseudo		 *  random number generator to obscure any cycles.		 */		x = rb.randn*1103515245 ^ *r;		*p++ = rb.randn = x; 		if(++r == rb.ep)			r = rb.buf;		rb.rp = r;	}	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;	}	qunlock(&rb.l);	poperror(); 	Wakeup(&rb.clock);	Wakeup(&rb.producer); if(0)print("B");	return n;}