--- /dev/null	2016-04-26 16:08:43.098618272 +0100
+++ new/src/java.httpclient/share/classes/java/net/http/CharsetToolkit.java	2016-04-29 11:47:37.255376410 +0100
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2016, 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
+ */
+package java.net.http;
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.CoderResult;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+// The purpose of this class is to separate charset-related tasks from the main
+// WebSocket logic, simplifying where possible.
+//
+//     * Coders hide the differences between coding and flushing stages on the
+//       API level
+//     * Verifier abstracts the way the verification is performed
+//       (spoiler: it's a decoding into a throw-away buffer)
+//
+// Coding methods throw exceptions instead of returning coding result denoting
+// errors, since any kind of handling and recovery is not expected.
+final class CharsetToolkit {
+
+    private CharsetToolkit() { }
+
+    static final class Verifier {
+
+        private final CharsetDecoder decoder = UTF_8.newDecoder();
+        // A buffer used to check validity of UTF-8 byte stream by decoding it.
+        // The contents of this buffer are never used.
+        // The size is arbitrary, though it should probably be chosen from the
+        // performance perspective since it affects the total number of calls to
+        // decoder.decode() and amount of work in each of these calls
+        private final CharBuffer blackHole = CharBuffer.allocate(1024);
+
+        void verify(ByteBuffer in, boolean endOfInput)
+                throws CharacterCodingException {
+            while (true) {
+                // Since decoder.flush() cannot produce an error, it's not
+                // helpful for verification. Therefore this step is skipped.
+                CoderResult r = decoder.decode(in, blackHole, endOfInput);
+                if (r.isOverflow()) {
+                    blackHole.clear();
+                } else if (r.isUnderflow()) {
+                    break;
+                } else if (r.isError()) {
+                    r.throwException();
+                } else {
+                    // Should not happen
+                    throw new InternalError();
+                }
+            }
+        }
+
+        Verifier reset() {
+            decoder.reset();
+            return this;
+        }
+    }
+
+    static final class Encoder {
+
+        private final CharsetEncoder encoder = UTF_8.newEncoder();
+        private boolean coding = true;
+
+        CoderResult encode(CharBuffer in, ByteBuffer out, boolean endOfInput)
+                throws CharacterCodingException {
+
+            if (coding) {
+                CoderResult r = encoder.encode(in, out, endOfInput);
+                if (r.isOverflow()) {
+                    return r;
+                } else if (r.isUnderflow()) {
+                    if (endOfInput) {
+                        coding = false;
+                    } else {
+                        return r;
+                    }
+                } else if (r.isError()) {
+                    r.throwException();
+                } else {
+                    // Should not happen
+                    throw new InternalError();
+                }
+            }
+            assert !coding;
+            return encoder.flush(out);
+        }
+
+        Encoder reset() {
+            coding = true;
+            encoder.reset();
+            return this;
+        }
+    }
+
+    static CharBuffer decode(ByteBuffer in) throws CharacterCodingException {
+        return UTF_8.newDecoder().decode(in);
+    }
+
+    static final class Decoder {
+
+        private final CharsetDecoder decoder = UTF_8.newDecoder();
+        private boolean coding = true; // Either coding or flushing
+
+        CoderResult decode(ByteBuffer in, CharBuffer out, boolean endOfInput)
+                throws CharacterCodingException {
+
+            if (coding) {
+                CoderResult r = decoder.decode(in, out, endOfInput);
+                if (r.isOverflow()) {
+                    return r;
+                } else if (r.isUnderflow()) {
+                    if (endOfInput) {
+                        coding = false;
+                    } else {
+                        return r;
+                    }
+                } else if (r.isError()) {
+                    r.throwException();
+                } else {
+                    // Should not happen
+                    throw new InternalError();
+                }
+            }
+            assert !coding;
+            return decoder.flush(out);
+        }
+
+        Decoder reset() {
+            coding = true;
+            decoder.reset();
+            return this;
+        }
+    }
+}