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	/*
	* Copyright (c) 2001, 2020, 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.reflect;

	import java.lang.reflect.*;
	import java.util.HashMap;
	import java.util.Map;
	import java.util.Objects;
	import java.util.Set;
	import jdk.internal.access.SharedSecrets;
	import jdk.internal.misc.VM;
	import jdk.internal.vm.annotation.IntrinsicCandidate;

	/** Common utility routines used by both java.lang and
	java.lang.reflect */

	public class Reflection {

	/** Used to filter out fields and methods from certain classes from public
	view, where they are sensitive or they may contain VM-internal objects.
	These Maps are updated very rarely. Rather than synchronize on
	each access, we use copy-on-write */
	private static volatile Map<Class<?>, Set<String>> fieldFilterMap;
	private static volatile Map<Class<?>, Set<String>> methodFilterMap;
	private static final String WILDCARD = "*";
	public static final Set<String> ALL_MEMBERS = Set.of(WILDCARD);

	static {
	fieldFilterMap = Map.of(
	Reflection.class, ALL_MEMBERS,
	AccessibleObject.class, ALL_MEMBERS,
	Class.class, Set.of("classLoader", "classData"),
	ClassLoader.class, ALL_MEMBERS,
	Constructor.class, ALL_MEMBERS,
	Field.class, ALL_MEMBERS,
	Method.class, ALL_MEMBERS,
	Module.class, ALL_MEMBERS,
	System.class, Set.of("security")
	);
	methodFilterMap = Map.of();
	}

	/** Returns the class of the caller of the method calling this method,
	ignoring frames associated with java.lang.reflect.Method.invoke()
	and its implementation. */
	@CallerSensitive
	@IntrinsicCandidate
	public static native Class<?> getCallerClass();

	/** Retrieves the access flags written to the class file. For
	inner classes these flags may differ from those returned by
	Class.getModifiers(), which searches the InnerClasses
	attribute to find the source-level access flags. This is used
	instead of Class.getModifiers() for run-time access checks due
	to compatibility reasons; see 4471811. Only the values of the
	low 13 bits (i.e., a mask of 0x1FFF) are guaranteed to be
	valid. */
	@IntrinsicCandidate
	public static native int getClassAccessFlags(Class<?> c);


	/**
	* Ensures that access to a member is granted and throws
	* IllegalAccessException if not.
	*
	* @param currentClass the class performing the access
	* @param memberClass the declaring class of the member being accessed
	* @param targetClass the class of target object if accessing instance
	* field or method;
	* or the declaring class if accessing constructor;
	* or null if accessing static field or method
	* @param modifiers the member's access modifiers
	* @throws IllegalAccessException if access to member is denied
	*/
	public static void ensureMemberAccess(Class<?> currentClass,
	Class<?> memberClass,
	Class<?> targetClass,
	int modifiers)
	throws IllegalAccessException
	{
	if (!verifyMemberAccess(currentClass, memberClass, targetClass, modifiers)) {
	throw newIllegalAccessException(currentClass, memberClass, targetClass, modifiers);
	}
	}

	public static void ensureNativeAccess(Class<?> currentClass) {
	Module module = currentClass.getModule();
	if (!SharedSecrets.getJavaLangAccess().isEnableNativeAccess(module)) {
	throw new IllegalCallerException("Illegal native access from: " + module);
	}
	}

	/**
	* Verify access to a member and return {@code true} if it is granted.
	*
	* @param currentClass the class performing the access
	* @param memberClass the declaring class of the member being accessed
	* @param targetClass the class of target object if accessing instance
	* field or method;
	* or the declaring class if accessing constructor;
	* or null if accessing static field or method
	* @param modifiers the member's access modifiers
	* @return {@code true} if access to member is granted
	*/
	public static boolean verifyMemberAccess(Class<?> currentClass,
	Class<?> memberClass,
	Class<?> targetClass,
	int modifiers)
	{
	Objects.requireNonNull(currentClass);
	Objects.requireNonNull(memberClass);

	if (currentClass == memberClass) {
	// Always succeeds
	return true;
	}

	if (!verifyModuleAccess(currentClass.getModule(), memberClass)) {
	return false;
	}

	boolean gotIsSameClassPackage = false;
	boolean isSameClassPackage = false;

	if (!Modifier.isPublic(getClassAccessFlags(memberClass))) {
	isSameClassPackage = isSameClassPackage(currentClass, memberClass);
	gotIsSameClassPackage = true;
	if (!isSameClassPackage) {
	return false;
	}
	}

	// At this point we know that currentClass can access memberClass.

	if (Modifier.isPublic(modifiers)) {
	return true;
	}

	// Check for nestmate access if member is private
	if (Modifier.isPrivate(modifiers)) {
	// Note: targetClass may be outside the nest, but that is okay
	// as long as memberClass is in the nest.
	if (areNestMates(currentClass, memberClass)) {
	return true;
	}
	}

	boolean successSoFar = false;

	if (Modifier.isProtected(modifiers)) {
	// See if currentClass is a subclass of memberClass
	if (isSubclassOf(currentClass, memberClass)) {
	successSoFar = true;
	}
	}

	if (!successSoFar && !Modifier.isPrivate(modifiers)) {
	if (!gotIsSameClassPackage) {
	isSameClassPackage = isSameClassPackage(currentClass,
	memberClass);
	gotIsSameClassPackage = true;
	}

	if (isSameClassPackage) {
	successSoFar = true;
	}
	}

	if (!successSoFar) {
	return false;
	}

	// Additional test for protected instance members
	// and protected constructors: JLS 6.6.2
	if (targetClass != null && Modifier.isProtected(modifiers) &&
	targetClass != currentClass)
	{
	if (!gotIsSameClassPackage) {
	isSameClassPackage = isSameClassPackage(currentClass, memberClass);
	gotIsSameClassPackage = true;
	}
	if (!isSameClassPackage) {
	if (!isSubclassOf(targetClass, currentClass)) {
	return false;
	}
	}
	}

	return true;
	}

	/*
	* Verify if a member is public and memberClass is a public type
	* in a package that is unconditionally exported and
	* return {@code true} if it is granted.
	*
	* @param memberClass the declaring class of the member being accessed
	* @param modifiers the member's access modifiers
	* @return {@code true} if the member is public and in a publicly accessible type
	*/
	public static boolean verifyPublicMemberAccess(Class<?> memberClass, int modifiers) {
	Module m = memberClass.getModule();
	return Modifier.isPublic(modifiers)
	&& m.isExported(memberClass.getPackageName())
	&& Modifier.isPublic(Reflection.getClassAccessFlags(memberClass));
	}

	/**
	* Returns {@code true} if memberClass's module exports memberClass's
	* package to currentModule.
	*/
	public static boolean verifyModuleAccess(Module currentModule, Class<?> memberClass) {
	Module memberModule = memberClass.getModule();
	if (currentModule == memberModule) {
	// same module (named or unnamed) or both null if called
	// before module system is initialized, which means we are
	// dealing with java.base only.
	return true;
	} else {
	String pkg = memberClass.getPackageName();
	return memberModule.isExported(pkg, currentModule);
	}
	}

	/**
	* Returns true if two classes in the same package.
	*/
	private static boolean isSameClassPackage(Class<?> c1, Class<?> c2) {
	if (c1.getClassLoader() != c2.getClassLoader())
	return false;
	return Objects.equals(c1.getPackageName(), c2.getPackageName());
	}

	static boolean isSubclassOf(Class<?> queryClass,
	Class<?> ofClass)
	{
	while (queryClass != null) {
	if (queryClass == ofClass) {
	return true;
	}
	queryClass = queryClass.getSuperclass();
	}
	return false;
	}

	// fieldNames must contain only interned Strings
	public static synchronized void registerFieldsToFilter(Class<?> containingClass,
	Set<String> fieldNames) {
	fieldFilterMap =
	registerFilter(fieldFilterMap, containingClass, fieldNames);
	}

	// methodNames must contain only interned Strings
	public static synchronized void registerMethodsToFilter(Class<?> containingClass,
	Set<String> methodNames) {
	methodFilterMap =
	registerFilter(methodFilterMap, containingClass, methodNames);
	}

	private static Map<Class<?>, Set<String>> registerFilter(Map<Class<?>, Set<String>> map,
	Class<?> containingClass,
	Set<String> names) {
	if (map.get(containingClass) != null) {
	throw new IllegalArgumentException
	("Filter already registered: " + containingClass);
	}
	map = new HashMap<>(map);
	map.put(containingClass, Set.copyOf(names));
	return map;
	}

	public static Field[] filterFields(Class<?> containingClass, Field[] fields) {
	if (fieldFilterMap == null) {
	// Bootstrapping
	return fields;
	}
	return (Field[])filter(fields, fieldFilterMap.get(containingClass));
	}

	public static Method[] filterMethods(Class<?> containingClass, Method[] methods) {
	if (methodFilterMap == null) {
	// Bootstrapping
	return methods;
	}
	return (Method[])filter(methods, methodFilterMap.get(containingClass));
	}

	private static Member[] filter(Member[] members, Set<String> filteredNames) {
	if ((filteredNames == null) \|\| (members.length == 0)) {
	return members;
	}
	Class<?> memberType = members[0].getClass();
	if (filteredNames.contains(WILDCARD)) {
	return (Member[]) Array.newInstance(memberType, 0);
	}
	int numNewMembers = 0;
	for (Member member : members) {
	if (!filteredNames.contains(member.getName())) {
	++numNewMembers;
	}
	}
	Member[] newMembers = (Member[])Array.newInstance(memberType, numNewMembers);
	int destIdx = 0;
	for (Member member : members) {
	if (!filteredNames.contains(member.getName())) {
	newMembers[destIdx++] = member;
	}
	}
	return newMembers;
	}

	/**
	* Tests if the given method is caller-sensitive and the declaring class
	* is defined by either the bootstrap class loader or platform class loader.
	*/
	public static boolean isCallerSensitive(Method m) {
	final ClassLoader loader = m.getDeclaringClass().getClassLoader();
	if (VM.isSystemDomainLoader(loader)) {
	return m.isAnnotationPresent(CallerSensitive.class);
	}
	return false;
	}

	/*
	* Tests if the given Field is a trusted final field and it cannot be
	* modified reflectively regardless of the value of its accessible flag.
	*/
	public static boolean isTrustedFinalField(Field field) {
	return SharedSecrets.getJavaLangReflectAccess().isTrustedFinalField(field);
	}

	/**
	* Returns an IllegalAccessException with an exception message based on
	* the access that is denied.
	*/
	public static IllegalAccessException newIllegalAccessException(Class<?> currentClass,
	Class<?> memberClass,
	Class<?> targetClass,
	int modifiers)
	{
	if (currentClass == null)
	return newIllegalAccessException(memberClass, modifiers);

	String currentSuffix = "";
	String memberSuffix = "";
	Module m1 = currentClass.getModule();
	if (m1.isNamed())
	currentSuffix = " (in " + m1 + ")";
	Module m2 = memberClass.getModule();
	if (m2.isNamed())
	memberSuffix = " (in " + m2 + ")";

	String memberPackageName = memberClass.getPackageName();

	String msg = currentClass + currentSuffix + " cannot access ";
	if (m2.isExported(memberPackageName, m1)) {

	// module access okay so include the modifiers in the message
	msg += "a member of " + memberClass + memberSuffix +
	" with modifiers \"" + Modifier.toString(modifiers) + "\"";

	} else {
	// module access failed
	msg += memberClass + memberSuffix+ " because "
	+ m2 + " does not export " + memberPackageName;
	if (m2.isNamed()) msg += " to " + m1;
	}

	return new IllegalAccessException(msg);
	}

	/**
	* Returns an IllegalAccessException with an exception message where
	* there is no caller frame.
	*/
	private static IllegalAccessException newIllegalAccessException(Class<?> memberClass,
	int modifiers)
	{
	String memberSuffix = "";
	Module m2 = memberClass.getModule();
	if (m2.isNamed())
	memberSuffix = " (in " + m2 + ")";

	String memberPackageName = memberClass.getPackageName();

	String msg = "JNI attached native thread (null caller frame) cannot access ";
	if (m2.isExported(memberPackageName)) {

	// module access okay so include the modifiers in the message
	msg += "a member of " + memberClass + memberSuffix +
	" with modifiers \"" + Modifier.toString(modifiers) + "\"";

	} else {
	// module access failed
	msg += memberClass + memberSuffix+ " because "
	+ m2 + " does not export " + memberPackageName;
	}

	return new IllegalAccessException(msg);
	}

	/**
	* Returns true if {@code currentClass} and {@code memberClass}
	* are nestmates - that is, if they have the same nesthost as
	* determined by the VM.
	*/
	public static native boolean areNestMates(Class<?> currentClass,
	Class<?> memberClass);
	}

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