kernel: move duplicated random.c to port

1 files changed, 138 insertions, 0 deletions

diff --git a/sys/src/9/port/random.c b/sys/src/9/port/random.c
new file mode 100644
index 000000000..3a697827a
--- /dev/null
+++ b/sys/src/9/port/random.c
@@ -0,0 +1,138 @@
+#include	"u.h"
+#include	"../port/lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"../port/error.h"
+
+struct Rb
+{
+	QLock;
+	Rendez	producer;
+	Rendez	consumer;
+	ulong	randomcount;
+	uchar	buf[128];
+	uchar	*ep;
+	uchar	*rp;
+	uchar	*wp;
+	uchar	next;
+	uchar	wakeme;
+	ushort	bits;
+	ulong	randn;
+} rb;
+
+static int
+rbnotfull(void*)
+{
+	int i;
+
+	i = rb.rp - rb.wp;
+	return i != 1 && i != (1 - sizeof(rb.buf));
+}
+
+static int
+rbnotempty(void*)
+{
+	return rb.wp != rb.rp;
+}
+
+static void
+genrandom(void*)
+{
+	up->basepri = PriNormal;
+	up->priority = up->basepri;
+
+	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)
+{
+	if(rb.randomcount == 0 || !rbnotfull(0))
+		return;
+
+	rb.bits = (rb.bits<<2) ^ rb.randomcount;
+	rb.randomcount = 0;
+
+	rb.next++;
+	if(rb.next != 8/2)
+		return;
+	rb.next = 0;
+
+	*rb.wp ^= rb.bits;
+	if(rb.wp+1 == rb.ep)
+		rb.wp = rb.buf;
+	else
+		rb.wp = rb.wp+1;
+
+	if(rb.wakeme)
+		wakeup(&rb.consumer);
+}
+
+void
+randominit(void)
+{
+	/* Frequency close but not equal to HZ */
+	addclock0link(randomclock, MS2HZ+3);
+	rb.ep = rb.buf + sizeof(rb.buf);
+	rb.rp = rb.wp = rb.buf;
+	kproc("genrandom", genrandom, 0);
+}
+
+/*
+ *  consume random bytes from a circular buffer
+ */
+ulong
+randomread(void *xp, ulong n)
+{
+	uchar *e, *p;
+	ulong x;
+
+	p = xp;
+
+	if(waserror()){
+		qunlock(&rb);
+		nexterror();
+	}
+
+	qlock(&rb);
+	for(e = p + n; p < e; ){
+		if(rb.wp == rb.rp){
+			rb.wakeme = 1;
+			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 ^ *rb.rp;
+		*p++ = rb.randn = x;
+
+		if(rb.rp+1 == rb.ep)
+			rb.rp = rb.buf;
+		else
+			rb.rp = rb.rp+1;
+	}
+	qunlock(&rb);
+	poperror();
+
+	wakeup(&rb.producer);
+
+	return n;
+}