diff -r f7fd051519ac -r ee6f7a61f3a5 src/java.net.http/share/classes/jdk/internal/net/http/hpack/StringWriter.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/jdk/internal/net/http/hpack/StringWriter.java	Tue Apr 17 08:54:17 2018 -0700
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2015, 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.nio.ByteBuffer;
+import java.util.Arrays;
+
+//
+//          0   1   2   3   4   5   6   7
+//        +---+---+---+---+---+---+---+---+
+//        | H |    String Length (7+)     |
+//        +---+---------------------------+
+//        |  String Data (Length octets)  |
+//        +-------------------------------+
+//
+// StringWriter does not require a notion of endOfInput (isLast) in 'write'
+// methods due to the nature of string representation in HPACK. Namely, the
+// length of the string is put before string's contents. Therefore the length is
+// always known beforehand.
+//
+// Expected use:
+//
+//     configure write* (reset configure write*)*
+//
+final class StringWriter {
+
+    private static final int NEW            = 0;
+    private static final int CONFIGURED     = 1;
+    private static final int LENGTH_WRITTEN = 2;
+    private static final int DONE           = 4;
+
+    private final IntegerWriter intWriter = new IntegerWriter();
+    private final Huffman.Writer huffmanWriter = new Huffman.Writer();
+    private final ISO_8859_1.Writer plainWriter = new ISO_8859_1.Writer();
+
+    private int state = NEW;
+    private boolean huffman;
+
+    StringWriter configure(CharSequence input, boolean huffman) {
+        return configure(input, 0, input.length(), huffman);
+    }
+
+    StringWriter configure(CharSequence input,
+                           int start,
+                           int end,
+                           boolean huffman) {
+        if (start < 0 || end < 0 || end > input.length() || start > end) {
+            throw new IndexOutOfBoundsException(
+                    String.format("input.length()=%s, start=%s, end=%s",
+                            input.length(), start, end));
+        }
+        if (!huffman) {
+            plainWriter.configure(input, start, end);
+            intWriter.configure(end - start, 7, 0b0000_0000);
+        } else {
+            huffmanWriter.from(input, start, end);
+            intWriter.configure(Huffman.INSTANCE.lengthOf(input, start, end),
+                    7, 0b1000_0000);
+        }
+
+        this.huffman = huffman;
+        state = CONFIGURED;
+        return this;
+    }
+
+    boolean write(ByteBuffer output) {
+        if (state == DONE) {
+            return true;
+        }
+        if (state == NEW) {
+            throw new IllegalStateException("Configure first");
+        }
+        if (!output.hasRemaining()) {
+            return false;
+        }
+        if (state == CONFIGURED) {
+            if (intWriter.write(output)) {
+                state = LENGTH_WRITTEN;
+            } else {
+                return false;
+            }
+        }
+        if (state == LENGTH_WRITTEN) {
+            boolean written = huffman
+                    ? huffmanWriter.write(output)
+                    : plainWriter.write(output);
+            if (written) {
+                state = DONE;
+                return true;
+            } else {
+                return false;
+            }
+        }
+        throw new InternalError(Arrays.toString(new Object[]{state, huffman}));
+    }
+
+    void reset() {
+        intWriter.reset();
+        if (huffman) {
+            huffmanWriter.reset();
+        } else {
+            plainWriter.reset();
+        }
+        state = NEW;
+    }
+}