/*

 * 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

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 */

package sun.reflect;

import java.lang.reflect.*;

import java.util.HashMap;

import java.util.Map;

/** 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<?>,String[]> fieldFilterMap;

    private static volatile Map<Class<?>,String[]> methodFilterMap;

    static {

        Map<Class<?>,String[]> map = new HashMap<Class<?>,String[]>();

        map.put(Reflection.class,

            new String[] {"fieldFilterMap", "methodFilterMap"});

        map.put(System.class, new String[] {"security"});

        fieldFilterMap = map;

        methodFilterMap = new HashMap<>();

    }

    /** Returns the class of the method <code>realFramesToSkip</code>

        frames up the stack (zero-based), ignoring frames associated

        with java.lang.reflect.Method.invoke() and its implementation.

        The first frame is that associated with this method, so

        <code>getCallerClass(0)</code> returns the Class object for

        sun.reflect.Reflection. Frames associated with

        java.lang.reflect.Method.invoke() and its implementation are

        completely ignored and do not count toward the number of "real"

        frames skipped. */

    public static native Class<?> getCallerClass(int realFramesToSkip);

    /** 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. */

    private static native int getClassAccessFlags(Class<?> c);

    /** A quick "fast-path" check to try to avoid getCallerClass()

        calls. */

    public static boolean quickCheckMemberAccess(Class<?> memberClass,

                                                 int modifiers)

    {

        return Modifier.isPublic(getClassAccessFlags(memberClass) & modifiers);

    }

    public static void ensureMemberAccess(Class<?> currentClass,

                                          Class<?> memberClass,

                                          Object target,

                                          int modifiers)

        throws IllegalAccessException

    {

        if (currentClass == null || memberClass == null) {

            throw new InternalError();

        }

        if (!verifyMemberAccess(currentClass, memberClass, target, modifiers)) {

            throw new IllegalAccessException("Class " + currentClass.getName() +

                                             " can not access a member of class " +

                                             memberClass.getName() +

                                             " with modifiers \"" +

                                             Modifier.toString(modifiers) +

                                             "\"");

        }

    }

    public static boolean verifyMemberAccess(Class<?> currentClass,

                                             // Declaring class of field

                                             // or method

                                             Class<?> memberClass,

                                             // May be NULL in case of statics

                                             Object   target,

                                             int      modifiers)

    {

        // Verify that currentClass can access a field, method, or

        // constructor of memberClass, where that member's access bits are

        // "modifiers".

        boolean gotIsSameClassPackage = false;

        boolean isSameClassPackage = false;

        if (currentClass == memberClass) {

            // Always succeeds

            return true;

        }

        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;

        }

        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;

        }

        if (Modifier.isProtected(modifiers)) {

            // Additional test for protected members: JLS 6.6.2

            Class<?> targetClass = (target == null ? memberClass : target.getClass());

            if (targetClass != currentClass) {

                if (!gotIsSameClassPackage) {

                    isSameClassPackage = isSameClassPackage(currentClass, memberClass);

                    gotIsSameClassPackage = true;

                }

                if (!isSameClassPackage) {

                    if (!isSubclassOf(targetClass, currentClass)) {

                        return false;

                    }

                }

            }

        }

        return true;

    }

    private static boolean isSameClassPackage(Class<?> c1, Class<?> c2) {

        return isSameClassPackage(c1.getClassLoader(), c1.getName(),

                                  c2.getClassLoader(), c2.getName());

    }

    /** Returns true if two classes are in the same package; classloader

        and classname information is enough to determine a class's package */

    private static boolean isSameClassPackage(ClassLoader loader1, String name1,

                                              ClassLoader loader2, String name2)

    {

        if (loader1 != loader2) {

            return false;

        } else {

            int lastDot1 = name1.lastIndexOf('.');

            int lastDot2 = name2.lastIndexOf('.');

            if ((lastDot1 == -1) || (lastDot2 == -1)) {

                // One of the two doesn't have a package.  Only return true

                // if the other one also doesn't have a package.

                return (lastDot1 == lastDot2);

            } else {

                int idx1 = 0;

                int idx2 = 0;

                // Skip over '['s

                if (name1.charAt(idx1) == '[') {

                    do {

                        idx1++;

                    } while (name1.charAt(idx1) == '[');

                    if (name1.charAt(idx1) != 'L') {

                        // Something is terribly wrong.  Shouldn't be here.

                        throw new InternalError("Illegal class name " + name1);

                    }

                }

                if (name2.charAt(idx2) == '[') {

                    do {

                        idx2++;

                    } while (name2.charAt(idx2) == '[');

                    if (name2.charAt(idx2) != 'L') {

                        // Something is terribly wrong.  Shouldn't be here.

                        throw new InternalError("Illegal class name " + name2);

                    }

                }

                // Check that package part is identical

                int length1 = lastDot1 - idx1;

                int length2 = lastDot2 - idx2;

                if (length1 != length2) {

                    return false;

                }

                return name1.regionMatches(false, idx1, name2, idx2, length1);

            }

        }

    }

    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,

                                              String ... fieldNames) {

        fieldFilterMap =

            registerFilter(fieldFilterMap, containingClass, fieldNames);

    }

    // methodNames must contain only interned Strings

    public static synchronized void registerMethodsToFilter(Class<?> containingClass,

                                              String ... methodNames) {

        methodFilterMap =

            registerFilter(methodFilterMap, containingClass, methodNames);

    }

    private static Map<Class<?>,String[]> registerFilter(Map<Class<?>,String[]> map,

            Class<?> containingClass, String ... names) {

        if (map.get(containingClass) != null) {

            throw new IllegalArgumentException

                            ("Filter already registered: " + containingClass);

        }

        map = new HashMap<Class<?>,String[]>(map);

        map.put(containingClass, 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, String[] filteredNames) {

        if ((filteredNames == null) || (members.length == 0)) {

            return members;

        }

        int numNewMembers = 0;

        for (Member member : members) {

            boolean shouldSkip = false;

            for (String filteredName : filteredNames) {

                if (member.getName() == filteredName) {

                    shouldSkip = true;

                    break;

                }

            }

            if (!shouldSkip) {

                ++numNewMembers;

            }

        }

        Member[] newMembers =

            (Member[])Array.newInstance(members[0].getClass(), numNewMembers);

        int destIdx = 0;

        for (Member member : members) {

            boolean shouldSkip = false;

            for (String filteredName : filteredNames) {

                if (member.getName() == filteredName) {

                    shouldSkip = true;

                    break;

                }

            }

            if (!shouldSkip) {

                newMembers[destIdx++] = member;

            }

        }

        return newMembers;

    }

}