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.codegen;

    26 

    27 import java.io.ByteArrayOutputStream;

    28 import java.io.IOException;

    29 import java.io.ObjectOutputStream;

    30 import java.util.Collections;

    31 import java.util.zip.Deflater;

    32 import java.util.zip.DeflaterOutputStream;

    33 import jdk.nashorn.internal.ir.Block;

    34 import jdk.nashorn.internal.ir.FunctionNode;

    35 import jdk.nashorn.internal.ir.LexicalContext;

    36 import jdk.nashorn.internal.ir.Node;

    37 import jdk.nashorn.internal.ir.Statement;

    38 import jdk.nashorn.internal.ir.visitor.NodeVisitor;

    39 import jdk.nashorn.internal.runtime.options.Options;

    40 

    41 /**

    42  * This static utility class performs serialization of FunctionNode ASTs to a byte array.

    43  * The format is a standard Java serialization stream, deflated.

    44  */

    45 final class AstSerializer {

    46     // Experimentally, we concluded that compression level 4 gives a good tradeoff between serialization speed

    47     // and size.

    48     private static final int COMPRESSION_LEVEL = Options.getIntProperty("nashorn.serialize.compression", 4);

    49     static byte[] serialize(final FunctionNode fn) {

    50         final ByteArrayOutputStream out = new ByteArrayOutputStream();

    51         final Deflater deflater = new Deflater(COMPRESSION_LEVEL);

    52         try (final ObjectOutputStream oout = new ObjectOutputStream(new DeflaterOutputStream(out, deflater))) {

    53             oout.writeObject(removeInnerFunctionBodies(fn));

    54         } catch (final IOException e) {

    55             throw new AssertionError("Unexpected exception serializing function", e);

    56         } finally {

    57             deflater.end();

    58         }

    59         return out.toByteArray();

    60     }

    61 

    62     private static FunctionNode removeInnerFunctionBodies(final FunctionNode fn) {

    63         return (FunctionNode)fn.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

    64             @Override

    65             public Node leaveBlock(final Block block) {

    66                 if (lc.isFunctionBody() && lc.getFunction(block) != lc.getOutermostFunction()) {

    67                     return block.setStatements(lc, Collections.<Statement>emptyList());

    68                 }

    69                 return super.leaveBlock(block);

    70             }

    71         });

    72     }

    73 }