214 lines
7.9 KiB
Java
214 lines
7.9 KiB
Java
/*
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* Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @bug 7004029 8131915
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* @summary Ensure Scope impl can cope with hash collisions
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* @library /tools/javac/lib
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* @modules jdk.compiler/com.sun.tools.javac.api
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* jdk.compiler/com.sun.tools.javac.code:+open
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* jdk.compiler/com.sun.tools.javac.file
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* jdk.compiler/com.sun.tools.javac.tree
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* jdk.compiler/com.sun.tools.javac.util
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* @build DPrinter HashCollisionTest
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* @run main HashCollisionTest
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*/
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import java.lang.reflect.*;
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import java.io.*;
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import java.util.function.BiConsumer;
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import com.sun.source.util.Trees;
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import com.sun.tools.javac.api.JavacTrees;
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import com.sun.tools.javac.util.*;
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import com.sun.tools.javac.code.*;
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import com.sun.tools.javac.code.Scope.*;
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import com.sun.tools.javac.code.Symbol.*;
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import com.sun.tools.javac.file.JavacFileManager;
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import com.sun.tools.javac.tree.JCTree.JCImport;
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import com.sun.tools.javac.tree.TreeMaker;
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import static com.sun.tools.javac.code.Kinds.Kind.*;
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public class HashCollisionTest {
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public static void main(String... args) throws Exception {
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new HashCollisionTest().run();
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}
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void run() throws Exception {
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// set up basic environment for test
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Context context = new Context();
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JavacFileManager.preRegister(context); // required by ClassReader which is required by Symtab
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make = TreeMaker.instance(context);
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names = Names.instance(context); // Name.Table impls tied to an instance of Names
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symtab = Symtab.instance(context);
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trees = JavacTrees.instance(context);
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types = Types.instance(context);
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// determine hashMask for an empty scope
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Scope emptyScope = WriteableScope.create(symtab.unnamedModule.unnamedPackage); // any owner will do
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Field field = emptyScope.getClass().getDeclaredField("hashMask");
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field.setAccessible(true);
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scopeHashMask = field.getInt(emptyScope);
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log("scopeHashMask: " + scopeHashMask);
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// 1. determine the Name.hashCode of "Entry", and therefore the index of
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// Entry in an empty scope. i.e. name.hashCode() & Scope.hashMask
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Name entry = names.fromString("Entry");
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// 2. create names of the form *$Entry until we find a name with a
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// hashcode which yields the same index as Entry in an empty scope.
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// Since Name.hashCode is a function of position (and not content) it
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// should work to create successively longer names until one with the
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// desired characteristics is found.
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Name outerName;
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Name innerName;
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StringBuilder sb = new StringBuilder("C");
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int i = 0;
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do {
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sb.append(Integer.toString(i % 10));
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innerName = names.fromString(sb + "$Entry");
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} while (!clash(entry, innerName) && (++i) < MAX_TRIES);
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if (clash(entry, innerName)) {
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log("Detected expected hash collision for " + entry + " and " + innerName
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+ " after " + i + " tries");
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} else {
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throw new Exception("No potential collision found after " + i + " tries");
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}
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outerName = names.fromString(sb.toString());
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/*
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* Now we can set up the scenario.
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*/
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// 3. Create a nested class named Entry
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ClassSymbol cc = createClass(names.fromString("C"), symtab.unnamedModule.unnamedPackage);
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ClassSymbol ce = createClass(entry, cc);
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// 4. Create a package containing a nested class using the name from 2
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PackageSymbol p = new PackageSymbol(names.fromString("p"), symtab.rootPackage);
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p.members_field = WriteableScope.create(p);
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ClassSymbol inner = createClass(innerName, p);
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// we'll need this later when we "rename" cn
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ClassSymbol outer = createClass(outerName, p);
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// 5. Create a star-import scope
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log ("createStarImportScope");
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PackageSymbol pkg = new PackageSymbol(names.fromString("pkg"), symtab.rootPackage);
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StarImportScope starImportScope = new StarImportScope(pkg);
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dump("initial", starImportScope);
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// 6. Insert the contents of the package from 4.
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Scope fromScope = p.members();
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ImportFilter typeFilter = new ImportFilter() {
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@Override
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public boolean accepts(Scope origin, Symbol sym) {
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return sym.kind == TYP;
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}
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};
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BiConsumer<JCImport, CompletionFailure> noCompletionFailure =
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(imp, cf) -> { throw new IllegalStateException(); };
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starImportScope.importAll(types, fromScope, typeFilter, make.Import(null, false), noCompletionFailure);
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dump("imported p", starImportScope);
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// 7. Insert the class from 3.
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starImportScope.importAll(types, cc.members_field, typeFilter, make.Import(null, false), noCompletionFailure);
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dump("imported ce", starImportScope);
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/*
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* Set the trap.
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*/
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// 8. Rename the nested class to Entry. so that there is a bogus entry in the star-import scope
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p.members_field.remove(inner);
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inner.name = entry;
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inner.owner = outer;
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outer.members_field.enter(inner);
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// 9. Lookup Entry
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Symbol found = starImportScope.findFirst(entry);
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if (found != ce)
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throw new Exception("correct symbol not found: " + entry + "; found=" + found);
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dump("final", starImportScope);
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}
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/*
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* Check for a (probable) hash collision in an empty scope.
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*/
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boolean clash(Name n1, Name n2) {
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log(n1 + " hc:" + n1.hashCode() + " v:" + (n1.hashCode() & scopeHashMask) + ", " +
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n2 + " hc:" + n2.hashCode() + " v:" + (n2.hashCode() & scopeHashMask));
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return (n1.hashCode() & scopeHashMask) == (n2.hashCode() & scopeHashMask);
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}
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/**
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* Create a class symbol, init the members scope, and add it to owner's scope.
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*/
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ClassSymbol createClass(Name name, Symbol owner) {
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ClassSymbol sym = new ClassSymbol(0, name, owner);
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sym.members_field = WriteableScope.create(sym);
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if (owner != symtab.unnamedModule.unnamedPackage)
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owner.members().enter(sym);
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return sym;
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}
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/**
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* Dump the contents of a scope to System.err.
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*/
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void dump(String label, Scope s) throws Exception {
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PrintWriter pw = new PrintWriter(System.err);
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new DPrinter(pw, trees).printScope(label, s);
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pw.flush();
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}
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Object readField(Object scope, String fieldName) throws Exception {
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Field field = scope.getClass().getDeclaredField(fieldName);
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field.setAccessible(true);
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return field.get(scope);
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}
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/**
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* Write a message to stderr.
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*/
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void log(String msg) {
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System.err.println(msg);
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}
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int MAX_TRIES = 100; // max tries to find a hash clash before giving up.
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int scopeHashMask;
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TreeMaker make;
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Names names;
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Symtab symtab;
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Trees trees;
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Types types;
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}
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