--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/internal/common/Demand.java	Sun Nov 05 17:32:13 2017 +0000
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2017, 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.incubator.http.internal.common;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Encapsulates operations with demand (Reactive Streams).
+ *
+ * <p> Demand is the aggregated number of elements requested by a Subscriber
+ * which is yet to be delivered (fulfilled) by the Publisher.
+ */
+public final class Demand {
+
+    private final AtomicLong val = new AtomicLong();
+
+    /**
+     * Increases this demand by the specified positive value.
+     *
+     * @param n
+     *         increment {@code > 0}
+     *
+     * @return {@code true} iff prior to this operation this demand was fulfilled
+     */
+    public boolean increase(long n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException(String.valueOf(n));
+        }
+        long prev = val.getAndAccumulate(n, (p, i) -> p + i < 0 ? Long.MAX_VALUE : p + i);
+        return prev == 0;
+    }
+
+    /**
+     * Tries to decrease this demand by the specified positive value.
+     *
+     * <p> The actual value this demand has been decreased by might be less than
+     * {@code n}, including {@code 0} (no decrease at all).
+     *
+     * @param n
+     *         decrement {@code > 0}
+     *
+     * @return a value {@code m} ({@code 0 <= m <= n}) this demand has been
+     *         actually decreased by
+     */
+    public long decreaseAndGet(long n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException(String.valueOf(n));
+        }
+        long p, d;
+        do {
+            d = val.get();
+            p = Math.min(d, n);
+        } while (!val.compareAndSet(d, d - p));
+        return p;
+    }
+
+    /**
+     * Tries to decrease this demand by {@code 1}.
+     *
+     * @return {@code true} iff this demand has been decreased by {@code 1}
+     */
+    public boolean tryDecrement() {
+        return decreaseAndGet(1) == 1;
+    }
+
+    /**
+     * @return {@code true} iff there is no unfulfilled demand
+     */
+    public boolean isFulfilled() {
+        return val.get() == 0;
+    }
+
+    /**
+     * Resets this object to its initial state.
+     */
+    public void reset() {
+        val.set(0);
+    }
+
+    /**
+     * Returns the current value of this demand.
+     *
+     * @return the current value of this demand
+     */
+    public long get() {
+        return val.get();
+    }
+
+    @Override
+    public String toString() {
+        return String.valueOf(val.get());
+    }
+}