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 * and Distribution License("CDDL") (collectively, the "License").  You
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 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
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package com.sun.istack.tools;

import java.io.InputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.Enumeration;

/**
 * Load classes/resources from a side folder, so that
 * classes of the same package can live in a single jar file.
 *
 * 
 * For example, with the following jar file:
 * 
 *  /
 *  +- foo
 *     +- X.class
 *  +- bar
 *     +- X.class
 * 
 * 
 * {@link ParallelWorldClassLoader}("foo/") would load X.class from
 * /foo/X.class (note that X is defined in the root package, not
 * foo.X.
 *
 * 

 * This can be combined with  {@link MaskingClassLoader} to mask classes which are loaded by the parent
 * class loader so that the child class loader
 * classes living in different folders are loaded
 * before the parent class loader loads classes living the jar file publicly
 * visible
 * For example, with the following jar file:
 * 
 *  /
 *  +- foo
 *     +- X.class
 *  +- bar
 *     +-foo
 *        +- X.class
 * 

 * 
 * {@link ParallelWorldClassLoader}(MaskingClassLoader.class.getClassLoader()) would load foo.X.class from
 * /bar/foo.X.class not the foo.X.class in the publicly visible place in the jar file, thus
 * masking the parent classLoader from loading the class from  foo.X.class
 * (note that X is defined in the  package foo, not
 * bar.foo.X.
 *
 * @author Kohsuke Kawaguchi
 */
public class ParallelWorldClassLoader extends ClassLoader {

    /**
     * Strings like "prefix/", "abc/", or "" to indicate
     * classes should be loaded normally.
     */
    private final String prefix;

    public ParallelWorldClassLoader(ClassLoader parent,String prefix) {
        super(parent);
        this.prefix = prefix;
    }

    protected Class findClass(String name) throws ClassNotFoundException {
        StringBuffer sb = new StringBuffer(name.length()+prefix.length()+6);
        sb.append(prefix).append(name.replace('.','/')).append(".class");

        InputStream is = getParent().getResourceAsStream(sb.toString());
        if (is==null)
            throw new ClassNotFoundException(name);

        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buf = new byte[1024];
            int len;
            while((len=is.read(buf))>=0)
                baos.write(buf,0,len);

            buf = baos.toByteArray();
            int packIndex = name.lastIndexOf('.');
            if (packIndex != -1) {
                String pkgname = name.substring(0, packIndex);
                // Check if package already loaded.
                Package pkg = getPackage(pkgname);
                if (pkg == null) {
                    definePackage(pkgname, null, null, null, null, null, null, null);
                }
            }
            return defineClass(name,buf,0,buf.length);
        } catch (IOException e) {
            throw new ClassNotFoundException(name,e);
        }
    }

    protected URL findResource(String name) {
        return getParent().getResource(prefix+name);
    }

    protected Enumeration findResources(String name) throws IOException {
        return getParent().getResources(    prefix+name);
    }

    /**
     * Given the URL inside jar, returns the URL to the jar itself.
     */
    public static URL toJarUrl(URL res) throws ClassNotFoundException, MalformedURLException {
        String url = res.toExternalForm();
        if(!url.startsWith("jar:"))
            throw new ClassNotFoundException("Loaded outside a jar "+url);
        url = url.substring(4); // cut off jar:
        url = url.substring(0,url.lastIndexOf('!'));    // cut off everything after '!'
        return new URL(url);
    }
}