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/*
 * Copyright (c) 2019, 2019, 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 com.oracle.svm.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

/**
 * This class contains utility methods for commonly used reflection functionality. Note that lookups
 * will not work on JDK 17 in cases when the field/method is filtered. See
 * jdk.internal.reflect.Reflection#fieldFilterMap for more information or
 * com.oracle.svm.hosted.ModuleLayerFeature for an example of a workaround in such cases.
 */
public final class ReflectionUtil {

    @SuppressWarnings("serial")
    public static final class ReflectionUtilError extends Error {
        private ReflectionUtilError(Throwable cause) {
            super(cause);
        }
    }

    private ReflectionUtil() {
    }

    /**
     * Ensure that this class is allowed to call setAccessible for an element of the provided
     * declaring class.
     */
    private static void openModule(Class declaringClass) {
        ModuleSupport.accessModuleByClass(ModuleSupport.Access.OPEN, ReflectionUtil.class, declaringClass);
    }

    public static Class lookupClass(boolean optional, String className) {
        try {
            return Class.forName(className, false, ReflectionUtil.class.getClassLoader());
        } catch (ClassNotFoundException ex) {
            if (optional) {
                return null;
            }
            throw new ReflectionUtilError(ex);
        }
    }

    public static Method lookupMethod(Class declaringClass, String methodName, Class... parameterTypes) {
        return lookupMethod(false, declaringClass, methodName, parameterTypes);
    }

    public static Method lookupMethod(boolean optional, Class declaringClass, String methodName, Class... parameterTypes) {
        try {
            Method result = declaringClass.getDeclaredMethod(methodName, parameterTypes);
            openModule(declaringClass);
            result.setAccessible(true);
            return result;
        } catch (ReflectiveOperationException ex) {
            if (optional) {
                return null;
            }
            throw new ReflectionUtilError(ex);
        }
    }

    public static  Constructor lookupConstructor(Class declaringClass, Class... parameterTypes) {
        return lookupConstructor(false, declaringClass, parameterTypes);
    }

    public static  Constructor lookupConstructor(boolean optional, Class declaringClass, Class... parameterTypes) {
        try {
            Constructor result = declaringClass.getDeclaredConstructor(parameterTypes);
            openModule(declaringClass);
            result.setAccessible(true);
            return result;
        } catch (ReflectiveOperationException ex) {
            if (optional) {
                return null;
            }
            throw new ReflectionUtilError(ex);
        }
    }

    public static  T newInstance(Class declaringClass) {
        try {
            return lookupConstructor(declaringClass).newInstance();
        } catch (ReflectiveOperationException ex) {
            throw new ReflectionUtilError(ex);
        }
    }

    public static Field lookupField(Class declaringClass, String fieldName) {
        return lookupField(false, declaringClass, fieldName);
    }

    private static final Method fieldGetDeclaredFields0 = ReflectionUtil.lookupMethod(Class.class, "getDeclaredFields0", boolean.class);

    public static Field lookupField(boolean optional, Class declaringClass, String fieldName) {
        try {
            Field result = declaringClass.getDeclaredField(fieldName);
            openModule(declaringClass);
            result.setAccessible(true);
            return result;
        } catch (ReflectiveOperationException ex) {
            /* Try to get hidden field */
            try {
                Field[] allFields = (Field[]) fieldGetDeclaredFields0.invoke(declaringClass, false);
                for (Field field : allFields) {
                    if (field.getName().equals(fieldName)) {
                        openModule(declaringClass);
                        field.setAccessible(true);
                        return field;
                    }
                }
            } catch (ReflectiveOperationException e) {
                // ignore
            }
            if (optional) {
                return null;
            }
            throw new ReflectionUtilError(ex);
        }
    }

    @SuppressWarnings("unchecked")
    public static  T readField(Class declaringClass, String fieldName, Object receiver) {
        try {
            return (T) lookupField(declaringClass, fieldName).get(receiver);
        } catch (ReflectiveOperationException ex) {
            throw new ReflectionUtilError(ex);
        }
    }

    public static  T readStaticField(Class declaringClass, String fieldName) {
        return readField(declaringClass, fieldName, null);
    }
}