--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/hpack/IntegerReader.java	Wed Feb 07 21:45:37 2018 +0000
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2014, 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.hpack;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+import static java.lang.String.format;
+
+final class IntegerReader {
+
+    private static final int NEW             = 0;
+    private static final int CONFIGURED      = 1;
+    private static final int FIRST_BYTE_READ = 2;
+    private static final int DONE            = 4;
+
+    private int state = NEW;
+
+    private int N;
+    private int maxValue;
+    private int value;
+    private long r;
+    private long b = 1;
+
+    public IntegerReader configure(int N) {
+        return configure(N, Integer.MAX_VALUE);
+    }
+
+    //
+    // Why is it important to configure 'maxValue' here. After all we can wait
+    // for the integer to be fully read and then check it. Can't we?
+    //
+    // Two reasons.
+    //
+    // 1. Value wraps around long won't be unnoticed.
+    // 2. It can spit out an exception as soon as it becomes clear there's
+    // an overflow. Therefore, no need to wait for the value to be fully read.
+    //
+    public IntegerReader configure(int N, int maxValue) {
+        if (state != NEW) {
+            throw new IllegalStateException("Already configured");
+        }
+        checkPrefix(N);
+        if (maxValue < 0) {
+            throw new IllegalArgumentException(
+                    "maxValue >= 0: maxValue=" + maxValue);
+        }
+        this.maxValue = maxValue;
+        this.N = N;
+        state = CONFIGURED;
+        return this;
+    }
+
+    public boolean read(ByteBuffer input) throws IOException {
+        if (state == NEW) {
+            throw new IllegalStateException("Configure first");
+        }
+        if (state == DONE) {
+            return true;
+        }
+        if (!input.hasRemaining()) {
+            return false;
+        }
+        if (state == CONFIGURED) {
+            int max = (2 << (N - 1)) - 1;
+            int n = input.get() & max;
+            if (n != max) {
+                value = n;
+                state = DONE;
+                return true;
+            } else {
+                r = max;
+            }
+            state = FIRST_BYTE_READ;
+        }
+        if (state == FIRST_BYTE_READ) {
+            // variable-length quantity (VLQ)
+            byte i;
+            do {
+                if (!input.hasRemaining()) {
+                    return false;
+                }
+                i = input.get();
+                long increment = b * (i & 127);
+                if (r + increment > maxValue) {
+                    throw new IOException(format(
+                            "Integer overflow: maxValue=%,d, value=%,d",
+                            maxValue, r + increment));
+                }
+                r += increment;
+                b *= 128;
+            } while ((128 & i) == 128);
+
+            value = (int) r;
+            state = DONE;
+            return true;
+        }
+        throw new InternalError(Arrays.toString(
+                new Object[]{state, N, maxValue, value, r, b}));
+    }
+
+    public int get() throws IllegalStateException {
+        if (state != DONE) {
+            throw new IllegalStateException("Has not been fully read yet");
+        }
+        return value;
+    }
+
+    private static void checkPrefix(int N) {
+        if (N < 1 || N > 8) {
+            throw new IllegalArgumentException("1 <= N <= 8: N= " + N);
+        }
+    }
+
+    public IntegerReader reset() {
+        b = 1;
+        state = NEW;
+        return this;
+    }
+}