Mercurial > jdk8-mips64-public > langtools / file revision

 /*

  * 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;

 }