1 /*
   2  * Copyright (c) 2010, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package jdk.nashorn.internal.runtime;
  26 
  27 import java.io.ByteArrayOutputStream;
  28 import java.io.IOException;
  29 import java.io.ObjectOutputStream;
  30 import java.util.zip.Deflater;
  31 import java.util.zip.DeflaterOutputStream;
  32 import jdk.nashorn.internal.ir.FunctionNode;
  33 import jdk.nashorn.internal.runtime.options.Options;
  34 
  35 /**
  36  * This static utility class performs serialization of FunctionNode ASTs to a byte array.
  37  * The format is a standard Java serialization stream, deflated.
  38  */
  39 final class AstSerializer {
  40     // Experimentally, we concluded that compression level 4 gives a good tradeoff between serialization speed
  41     // and size.
  42     private static final int COMPRESSION_LEVEL = Options.getIntProperty("nashorn.serialize.compression", 4);
  43     static byte[] serialize(final FunctionNode fn) {
  44         final ByteArrayOutputStream out = new ByteArrayOutputStream();
  45         final Deflater deflater = new Deflater(COMPRESSION_LEVEL);
  46         try (final ObjectOutputStream oout = new ObjectOutputStream(new DeflaterOutputStream(out, deflater))) {
  47             oout.writeObject(fn);
  48         } catch (final IOException e) {
  49             throw new AssertionError("Unexpected exception serializing function", e);
  50         } finally {
  51             deflater.end();
  52         }
  53         return out.toByteArray();
  54     }
  55 }