/*

 * Copyright (c) 2010, 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.

 *

 * 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.

 */

/*

 * @test

 * @bug 7004029

 * @summary Ensure Scope impl can cope with hash collisions

 */

import java.lang.reflect.*;

import java.io.*;

import com.sun.tools.javac.util.*;

import com.sun.tools.javac.code.*;

import com.sun.tools.javac.code.Scope.*;

import com.sun.tools.javac.code.Symbol.*;

import com.sun.tools.javac.file.JavacFileManager;

import static com.sun.tools.javac.code.Kinds.*;

public class HashCollisionTest {

    public static void main(String... args) throws Exception {

        new HashCollisionTest().run();

    }

    void run() throws Exception {

        // set up basic environment for test

        Context context = new Context();

        JavacFileManager.preRegister(context); // required by ClassReader which is required by Symtab

        names = Names.instance(context);       // Name.Table impls tied to an instance of Names

        symtab = Symtab.instance(context);

        scopeCounter = ScopeCounter.instance(context);

        // determine hashMask for an empty scope

        Scope emptyScope = new Scope(symtab.unnamedPackage); // any owner will do

        Field sHashMask = Scope.class.getDeclaredField("hashMask");

        sHashMask.setAccessible(true);

        scopeHashMask = sHashMask.getInt(emptyScope);

        log("scopeHashMask: " + scopeHashMask);

        // 1. determine the Name.hashCode of "Entry", and therefore the index of

        // Entry in an empty scope.  i.e. name.hashCode() & Scope.hashMask

        Name entry = names.fromString("Entry");

        // 2. create names of the form *$Entry until we find a name with a

        // hashcode which yields the same index as Entry in an empty scope.

        // Since Name.hashCode is a function of position (and not content) it

        // should work to create successively longer names until one with the

        // desired characteristics is found.

        Name outerName;

        Name innerName;

        StringBuilder sb = new StringBuilder("C");

        int i = 0;

        do {

            sb.append(Integer.toString(i % 10));

            innerName = names.fromString(sb + "$Entry");

        } while (!clash(entry, innerName) && (++i) < MAX_TRIES);

        if (clash(entry, innerName)) {

            log("Detected expected hash collision for " + entry + " and " + innerName

                    + " after " + i + " tries");

        } else {

            throw new Exception("No potential collision found after " + i + " tries");

        }

        outerName = names.fromString(sb.toString());

        /*

         * Now we can set up the scenario.

         */

        // 3. Create a nested class named Entry

        ClassSymbol cc = createClass(names.fromString("C"), symtab.unnamedPackage);

        ClassSymbol ce = createClass(entry, cc);

        // 4. Create a package containing a nested class using the name from 2

        PackageSymbol p = new PackageSymbol(names.fromString("p"), symtab.rootPackage);

        p.members_field = new Scope(p);

        ClassSymbol inner = createClass(innerName, p);

        // we'll need this later when we "rename" cn

        ClassSymbol outer = createClass(outerName, p);

        // 5. Create a star-import scope

        log ("createStarImportScope");

        // if StarImportScope exists, use it, otherwise, for testing legacy code,

        // fall back on ImportScope

        Scope starImportScope;

        Method importAll;

        PackageSymbol pkg = new PackageSymbol(names.fromString("pkg"), symtab.rootPackage);

        try {

            Class<?> c = Class.forName("com.sun.tools.javac.code.Scope$StarImportScope");

            Constructor ctor = c.getDeclaredConstructor(new Class[] { Symbol.class });

            importAll = c.getDeclaredMethod("importAll", new Class[] { Scope.class });

            starImportScope = (Scope) ctor.newInstance(new Object[] { pkg });

        } catch (ClassNotFoundException e) {

            starImportScope = new ImportScope(pkg);

            importAll = null;

        }

        dump("initial", starImportScope);

        // 6. Insert the contents of the package from 4.

        Scope p_members = p.members();

        if (importAll != null) {

            importAll.invoke(starImportScope, p_members);

        } else {

            Scope fromScope = p_members;

            Scope toScope = starImportScope;

            // The following lines are taken from MemberEnter.importAll,

            // before the use of StarImportScope.importAll.

            for (Scope.Entry e = fromScope.elems; e != null; e = e.sibling) {

                if (e.sym.kind == TYP && !toScope.includes(e.sym))

                    toScope.enter(e.sym, fromScope);

            }

        }

        dump("imported p", starImportScope);

        // 7. Insert the class from 3.

        starImportScope.enter(ce, cc.members_field);

        dump("imported ce", starImportScope);

        /*

         * Set the trap.

         */

        // 8. Rename the nested class to Entry. so that there is a bogus entry in the star-import scope

        p.members_field.remove(inner);

        inner.name = entry;

        inner.owner = outer;

        outer.members_field.enter(inner);

        // 9. Lookup Entry

        Scope.Entry e = starImportScope.lookup(entry);

        dump("final", starImportScope);

        if (e.sym == null)

            throw new Exception("symbol not found: " + entry);

    }

    /*

     * Check for a (probable) hash collision in an empty scope.

     */

    boolean clash(Name n1, Name n2) {

        log(n1 + " hc:" + n1.hashCode() + " v:" + (n1.hashCode() & scopeHashMask) + ", " +

                n2 + " hc:" + n2.hashCode() + " v:" + (n2.hashCode() & scopeHashMask));

        return (n1.hashCode() & scopeHashMask) == (n2.hashCode() & scopeHashMask);

    }

    /**

     * Create a class symbol, init the members scope, and add it to owner's scope.

     */

    ClassSymbol createClass(Name name, Symbol owner) {

        ClassSymbol sym = new ClassSymbol(0, name, owner);

        sym.members_field = new ClassScope(sym, scopeCounter);

        if (owner != symtab.unnamedPackage)

            owner.members().enter(sym);

        return sym;

    }

    /**

     * Dump the contents of a scope to System.err.

     */

    void dump(String label, Scope s) throws Exception {

        dump(label, s, System.err);

    }

    /**

     * Dump the contents of a scope to a stream.

     */

    void dump(String label, Scope s, PrintStream out) throws Exception {

        out.println(label);

        Field sTable = Scope.class.getDeclaredField("table");

        sTable.setAccessible(true);

        out.println("owner:" + s.owner);

        Scope.Entry[] table = (Scope.Entry[]) sTable.get(s);

        for (int i = 0; i < table.length; i++) {

            if (i > 0)

                out.print(", ");

            out.print(i + ":" + toString(table[i], table, false));

        }

        out.println();

    }

    /**

     * Create a string showing the contents of an entry, using the table

     * to help identify cross-references to other entries in the table.

     * @param e the entry to be shown

     * @param table the table containing the other entries

     */

    String toString(Scope.Entry e, Scope.Entry[] table, boolean ref) {

        if (e == null)

            return "null";

        if (e.sym == null)

            return "sent"; // sentinel

        if (ref) {

            int index = indexOf(table, e);

            if (index != -1)

                return String.valueOf(index);

        }

        return "(" + e.sym.name + ":" + e.sym

                + ",shdw:" + toString(e.next(), table, true)

                + ",sibl:" + toString(e.sibling, table, true)

                + ((e.sym.owner != e.scope.owner)

                    ? (",BOGUS[" + e.sym.owner + "," + e.scope.owner + "]")

                    : "")

                + ")";

    }

    <T> int indexOf(T[] array, T item) {

        for (int i = 0; i < array.length; i++) {

            if (array[i] == item)

                return i;

        }

        return -1;

    }

    /**

     * Write a message to stderr.

     */

    void log(String msg) {

        System.err.println(msg);

    }

    int MAX_TRIES = 100; // max tries to find a hash clash before giving up.

    int scopeHashMask;

    Names names;

    Symtab symtab;

    ScopeCounter scopeCounter;

}