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	/*
	* Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
	* 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.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.internal.module;

	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.lang.module.ModuleDescriptor.Version;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.List;
	import java.util.Set;

	import jdk.internal.org.objectweb.asm.Attribute;
	import jdk.internal.org.objectweb.asm.ClassReader;
	import jdk.internal.org.objectweb.asm.ClassVisitor;
	import jdk.internal.org.objectweb.asm.ClassWriter;
	import jdk.internal.org.objectweb.asm.ModuleVisitor;
	import jdk.internal.org.objectweb.asm.Opcodes;
	import jdk.internal.org.objectweb.asm.commons.ModuleHashesAttribute;
	import jdk.internal.org.objectweb.asm.commons.ModuleResolutionAttribute;
	import jdk.internal.org.objectweb.asm.commons.ModuleTargetAttribute;

	/**
	* Utility class to extend a module-info.class with additional attributes.
	*/

	public final class ModuleInfoExtender {

	// the input stream to read the original module-info.class
	private final InputStream in;

	// the packages in the ModulePackages attribute
	private Set<String> packages;

	// the value for the module version in the Module attribute
	private Version version;

	// the value of the ModuleMainClass attribute
	private String mainClass;

	// the value for the ModuleTarget attribute
	private String targetPlatform;

	// the hashes for the ModuleHashes attribute
	private ModuleHashes hashes;

	// the value of the ModuleResolution attribute
	private ModuleResolution moduleResolution;

	private ModuleInfoExtender(InputStream in) {
	this.in = in;
	}

	/**
	* Sets the packages for the ModulePackages attribute
	*
	* @apiNote This method does not check that the package names are legal
	* package names or that the set of packages is a super set of the
	* packages in the module.
	*/
	public ModuleInfoExtender packages(Set<String> packages) {
	this.packages = Collections.unmodifiableSet(packages);
	return this;
	}

	/**
	* Sets the value for the module version in the Module attribute
	*/
	public ModuleInfoExtender version(Version version) {
	this.version = version;
	return this;
	}

	/**
	* Sets the value of the ModuleMainClass attribute.
	*
	* @apiNote This method does not check that the main class is a legal
	* class name in a named package.
	*/
	public ModuleInfoExtender mainClass(String mainClass) {
	this.mainClass = mainClass;
	return this;
	}

	/**
	* Sets the value for the ModuleTarget attribute.
	*/
	public ModuleInfoExtender targetPlatform(String targetPlatform) {
	this.targetPlatform = targetPlatform;
	return this;
	}

	/**
	* The ModuleHashes attribute will be emitted to the module-info with
	* the hashes encapsulated in the given {@code ModuleHashes}
	* object.
	*/
	public ModuleInfoExtender hashes(ModuleHashes hashes) {
	this.hashes = hashes;
	return this;
	}

	/**
	* Sets the value for the ModuleResolution attribute.
	*/
	public ModuleInfoExtender moduleResolution(ModuleResolution mres) {
	this.moduleResolution = mres;
	return this;
	}

	/**
	* Outputs the modified module-info.class to the given output stream.
	* Once this method has been called then the Extender object should
	* be discarded.
	*/
	public void write(OutputStream out) throws IOException {
	// emit to the output stream
	out.write(toByteArray());
	}

	/**
	* Returns the bytes of the modified module-info.class.
	* Once this method has been called then the Extender object should
	* be discarded.
	*/
	public byte[] toByteArray() throws IOException {
	ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS
	+ ClassWriter.COMPUTE_FRAMES);

	ClassReader cr = new ClassReader(in);

	ClassVisitor cv = new ClassVisitor(Opcodes.ASM6, cw) {
	@Override
	public ModuleVisitor visitModule(String name, int flags, String version) {
	Version v = ModuleInfoExtender.this.version;
	String vs = (v != null) ? v.toString() : version;
	ModuleVisitor mv = super.visitModule(name, flags, vs);

	// ModuleMainClass attribute
	if (mainClass != null) {
	mv.visitMainClass(mainClass.replace('.', '/'));
	}

	// ModulePackages attribute
	if (packages != null) {
	packages.forEach(pn -> mv.visitPackage(pn.replace('.', '/')));
	}

	return new ModuleVisitor(Opcodes.ASM6, mv) {
	public void visitMainClass(String existingMainClass) {
	// skip main class if there is a new value
	if (mainClass == null) {
	super.visitMainClass(existingMainClass);
	}
	}
	public void visitPackage(String existingPackage) {
	// skip packages if there is a new set of packages
	if (packages == null) {
	super.visitPackage(existingPackage);
	}
	}
	};
	}
	@Override
	public void visitAttribute(Attribute attr) {
	String name = attr.type;
	// drop existing attributes if there are replacements
	if (name.equals(ClassFileConstants.MODULE_TARGET)
	&& targetPlatform != null)
	return;
	if (name.equals(ClassFileConstants.MODULE_RESOLUTION)
	&& moduleResolution != null)
	return;
	if (name.equals(ClassFileConstants.MODULE_HASHES)
	&& hashes != null)
	return;

	super.visitAttribute(attr);

	}
	};

	List<Attribute> attrs = new ArrayList<>();
	attrs.add(new ModuleTargetAttribute());
	attrs.add(new ModuleResolutionAttribute());
	attrs.add(new ModuleHashesAttribute());
	cr.accept(cv, attrs.toArray(new Attribute[0]), 0);

	// add ModuleTarget, ModuleResolution and ModuleHashes attributes
	if (targetPlatform != null) {
	cw.visitAttribute(new ModuleTargetAttribute(targetPlatform));
	}
	if (moduleResolution != null) {
	int flags = moduleResolution.value();
	cw.visitAttribute(new ModuleResolutionAttribute(flags));
	}
	if (hashes != null) {
	String algorithm = hashes.algorithm();
	List<String> names = new ArrayList<>();
	List<byte[]> values = new ArrayList<>();
	for (String name : hashes.names()) {
	names.add(name);
	values.add(hashes.hashFor(name));
	}
	cw.visitAttribute(new ModuleHashesAttribute(algorithm, names, values));
	}

	return cw.toByteArray();
	}

	/**
	* Returns an {@code Extender} that may be used to add additional
	* attributes to the module-info.class read from the given input
	* stream.
	*/
	public static ModuleInfoExtender newExtender(InputStream in) {
	return new ModuleInfoExtender(in);
	}

	}

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