1 files changed, 167 insertions, 0 deletions
diff --git a/emu/port/random.c b/emu/port/random.c
new file mode 100644
index 00000000..05ae2b9a
--- /dev/null
+++ b/emu/port/random.c
@@ -0,0 +1,167 @@
+#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 int
+rbnotfull(void *v)
+{
+	int i;
+
+	USED(v);
+	i = rb.wp - rb.rp;
+	if(i < 0)
+		i += sizeof(rb.buf);
+	return i < rb.target;
+}
+
+static int
+rbnotempty(void *v)
+{
+	USED(v);
+	return rb.wp != rb.rp;
+}
+
+/*
+ *  spin counting up
+ */
+static void
+genrandom(void *v)
+{
+	USED(v);
+	oslopri();
+	for(;;){
+		for(;;)
+			if(++rb.randomcount > 65535)
+				break;
+		if(!rbnotfull(0))
+			Sleep(&rb.producer, rbnotfull, 0);
+	}
+}
+
+/*
+ *  produce random bits in a circular buffer
+ */
+static void
+randomclock(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);
+	}
+}
+
+void
+randominit(void)
+{
+	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)
+{
+	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;
+}