--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/common/SubscriptionBase.java	Wed Feb 07 21:45:37 2018 +0000
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.internal.net.http.common;
+
+import java.util.concurrent.Flow;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Maintains subscription counter and provides primitives for
+ * - accessing window
+ * - reducing window when delivering items externally
+ * - resume delivery when window was zero previously
+ *
+ * @author mimcmah
+ */
+public class SubscriptionBase implements Flow.Subscription {
+
+    final Demand demand = new Demand();
+
+    final SequentialScheduler scheduler; // when window was zero and is opened, run this
+    final Runnable cancelAction; // when subscription cancelled, run this
+    final AtomicBoolean cancelled;
+
+    public SubscriptionBase(SequentialScheduler scheduler, Runnable cancelAction) {
+        this.scheduler = scheduler;
+        this.cancelAction = cancelAction;
+        this.cancelled = new AtomicBoolean(false);
+    }
+
+    @Override
+    public void request(long n) {
+        if (demand.increase(n))
+            scheduler.runOrSchedule();
+    }
+
+
+
+    @Override
+    public synchronized String toString() {
+        return "SubscriptionBase: window = " + demand.get() +
+                " cancelled = " + cancelled.toString();
+    }
+
+    /**
+     * Returns true if the window was reduced by 1. In that case
+     * items must be supplied to subscribers and the scheduler run
+     * externally. If the window could not be reduced by 1, then false
+     * is returned and the scheduler will run later when the window is updated.
+     */
+    public boolean tryDecrement() {
+        return demand.tryDecrement();
+    }
+
+    public long window() {
+        return demand.get();
+    }
+
+    @Override
+    public void cancel() {
+        if (cancelled.getAndSet(true))
+            return;
+        scheduler.stop();
+        cancelAction.run();
+    }
+}