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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

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 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

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 * 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.

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/*

 * @test

 * @summary Ensure Scope impl can cope with hash collisions

 * @library /tools/javac/lib

 * @modules jdk.compiler/com.sun.tools.javac.api

 *          jdk.compiler/com.sun.tools.javac.code

 *          jdk.compiler/com.sun.tools.javac.file

 *          jdk.compiler/com.sun.tools.javac.tree

 *          jdk.compiler/com.sun.tools.javac.util

 * @build DPrinter HashCollisionTest

 * @run main HashCollisionTest

 */

import java.lang.reflect.*;

import java.io.*;

import com.sun.source.util.Trees;

import com.sun.tools.javac.api.JavacTrees;

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.Kind.*;

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);

        trees = JavacTrees.instance(context);

        types = Types.instance(context);

        // determine hashMask for an empty scope

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

        Field field = emptyScope.getClass().getDeclaredField("hashMask");

        field.setAccessible(true);

        scopeHashMask = field.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 = WriteableScope.create(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");

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

        StarImportScope starImportScope = new StarImportScope(pkg);

        dump("initial", starImportScope);

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

        Scope fromScope = p.members();

        ImportFilter typeFilter = new ImportFilter() {

            @Override

            public boolean accepts(Scope origin, Symbol sym) {

                return sym.kind == TYP;

            }

        };

        dump("imported p", starImportScope);

        // 7. Insert the class from 3.

        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

        Symbol found = starImportScope.findFirst(entry);

        if (found != ce)

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

        dump("final", starImportScope);

    }

    /*

     * 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 = WriteableScope.create(sym);

        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 {

        PrintWriter pw = new PrintWriter(System.err);

        new DPrinter(pw, trees).printScope(label, s);

        pw.flush();

    }

    Object readField(Object scope, String fieldName) throws Exception {

        Field field = scope.getClass().getDeclaredField(fieldName);

        field.setAccessible(true);

        return field.get(scope);

    }

    /**

     * 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;

    Trees trees;

    Types types;

}