1 files changed, 64 insertions, 0 deletions
diff --git a/src/cmd/vbackup/queue.c b/src/cmd/vbackup/queue.c
new file mode 100644
index 00000000..91fa221d
--- /dev/null
+++ b/src/cmd/vbackup/queue.c
@@ -0,0 +1,64 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <venti.h>
+#include <diskfs.h>
+#include "queue.h"
+
+Queue*
+qalloc(void)
+{
+	Queue *q;
+
+	q = vtmallocz(sizeof(Queue));
+	q->r.l = &q->lk;
+	return q;
+}
+
+Block*
+qread(Queue *q, u32int *pbno)
+{
+	Block *db;
+	u32int bno;
+
+	qlock(&q->lk);
+	while(q->nel == 0 && !q->closed)
+		rsleep(&q->r);
+	if(q->nel == 0 && q->closed){
+		qunlock(&q->lk);
+		return nil;
+	}
+	db = q->el[q->ri].db;
+	bno = q->el[q->ri].bno;
+	if(++q->ri == MAXQ)
+		q->ri = 0;
+	if(q->nel-- == MAXQ/2)
+		rwakeup(&q->r);
+	qunlock(&q->lk);
+	*pbno = bno;
+	return db;
+}
+
+void
+qwrite(Queue *q, Block *db, u32int bno)
+{
+	qlock(&q->lk);
+	while(q->nel == MAXQ)
+		rsleep(&q->r);
+	q->el[q->wi].db = db;
+	q->el[q->wi].bno = bno;
+	if(++q->wi == MAXQ)
+		q->wi = 0;
+	if(q->nel++ == MAXQ/2)
+		rwakeup(&q->r);
+	qunlock(&q->lk);
+}
+
+void
+qclose(Queue *q)
+{
+	qlock(&q->lk);
+	q->closed = 1;
+	rwakeup(&q->r);
+	qunlock(&q->lk);
+}