AstSerializer.java

/*
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 * 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.
 *
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package jdk.nashorn.internal.runtime;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
import jdk.nashorn.internal.ir.FunctionNode;
import jdk.nashorn.internal.runtime.options.Options;

/**
 * This static utility class performs serialization of FunctionNode ASTs to a byte array.
 * The format is a standard Java serialization stream, deflated.
 */
final class AstSerializer {
    // Experimentally, we concluded that compression level 4 gives a good tradeoff between serialization speed
    // and size.
    private static final int COMPRESSION_LEVEL = Options.getIntProperty("nashorn.serialize.compression", 4);
    static byte[] serialize(final FunctionNode fn) {
        final ByteArrayOutputStream out = new ByteArrayOutputStream();
        final Deflater deflater = new Deflater(COMPRESSION_LEVEL);
        try (final ObjectOutputStream oout = new ObjectOutputStream(new DeflaterOutputStream(out, deflater))) {
            oout.writeObject(fn);
        } catch (final IOException e) {
            throw new AssertionError("Unexpected exception serializing function", e);
        } finally {
            deflater.end();
        }
        return out.toByteArray();
    }
}