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OpenJPA Kernel
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */
package org.apache.openjpa.enhance;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLDecoder;

import org.apache.xbean.asm4.ClassReader;
import org.apache.xbean.asm4.ClassWriter;
import serp.bytecode.BCClass;


/**
 * Use ASM to add required StackMapTable attribute to the byte code generated by
 * Serp.
 */
public final class AsmAdaptor {
    private static final int Java7_MajorVersion = 51;

    @SuppressWarnings("deprecation")
    public static void write(BCClass bc) throws IOException {
        if (bc.getMajorVersion() < Java7_MajorVersion) {
            bc.write();
        } else {
            String name = bc.getName();
            int dotIndex = name.lastIndexOf('.') + 1;
            name = name.substring(dotIndex);
            Class type = bc.getType();

            OutputStream out = new FileOutputStream(
                    URLDecoder.decode(type.getResource(name + ".class").getFile()));
            try {
                writeJava7(bc, out);
            } finally {
                out.flush();
                out.close();
            }
        }
    }

    public static void write(BCClass bc, File outFile) throws IOException {
        if (bc.getMajorVersion() < Java7_MajorVersion) {
            bc.write(outFile);
        } else {
            OutputStream out = new FileOutputStream(outFile);
            try {
                writeJava7(bc, out);
            } finally {
                out.flush();
                out.close();
            }
        }
    }

    public static byte[] toByteArray(BCClass bc, byte[] returnBytes) throws IOException {
        if (bc.getMajorVersion() >= Java7_MajorVersion) {
            returnBytes = toJava7ByteArray(bc, returnBytes);
        }
        return returnBytes;
    }

    private static void writeJava7(BCClass bc, OutputStream out) throws IOException {
        byte[] java7Bytes = toJava7ByteArray(bc, bc.toByteArray());
        out.write(java7Bytes);
    }

    private static byte[] toJava7ByteArray(BCClass bc, byte[] classBytes) throws IOException {
        ByteArrayInputStream bais = new ByteArrayInputStream(classBytes);
        BufferedInputStream bis = new BufferedInputStream(bais);

        ClassWriter cw = new BCClassWriter(ClassWriter.COMPUTE_FRAMES, bc.getClassLoader());
        ClassReader cr = new ClassReader(bis);
        cr.accept(cw, 0);
        return cw.toByteArray();
    }

    private static class BCClassWriter extends ClassWriter {
        private final ClassLoader _loader;

        BCClassWriter(int flags, ClassLoader loader) {
            super(flags);
            _loader = loader;
        }

        @Override
        protected String getCommonSuperClass(String type1, String type2) {
            Class class1;
            Class class2;
            try {
                class1 = _loader.loadClass(type1.replace('/', '.'));
                class2 = _loader.loadClass(type2.replace('/', '.'));
            } catch (ClassNotFoundException ex) {
                throw new RuntimeException(ex);
            }
            if (class1.isAssignableFrom(class2)) {
                return type1;
            }
            if (class2.isAssignableFrom(class1)) {
                return type2;
            }
            if (class1.isInterface() || class2.isInterface()) {
                return "java/lang/Object";
            }
            do {
                class1 = class1.getSuperclass();
            } while (!class1.isAssignableFrom(class2));
            return class1.getName().replace('.', '/');
        }
    }
}