soot.jimple.toolkits.pointer.nativemethods.JavaLangStringNative Maven / Gradle / Ivy

package soot.jimple.toolkits.pointer.nativemethods;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2003 Feng Qian
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program 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 Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import soot.SootMethod;
import soot.jimple.toolkits.pointer.representations.Environment;
import soot.jimple.toolkits.pointer.representations.ReferenceVariable;
import soot.jimple.toolkits.pointer.util.NativeHelper;

public class JavaLangStringNative extends NativeMethodClass {
  public JavaLangStringNative(NativeHelper helper) {
    super(helper);
  }

  /**
   * Implements the abstract method simulateMethod. It distributes the request to the corresponding methods by signatures.
   */
  public void simulateMethod(SootMethod method, ReferenceVariable thisVar, ReferenceVariable returnVar,
      ReferenceVariable params[]) {

    String subSignature = method.getSubSignature();

    if (subSignature.equals("java.lang.String intern()")) {
      java_lang_String_intern(method, thisVar, returnVar, params);
      return;

    } else {
      defaultMethod(method, thisVar, returnVar, params);
      return;

    }
  }

  /************************** java.lang.String ***********************/
  /**
   * Returns a canonical representation for the string object. A pool of strings, initially empty, is maintained privately by
   * the class String.
   *
   * When the intern method is invoked, if the pool already contains a * string equal to this String object as determined by
   * the * equals(Object) method, then the string from the pool is * returned. Otherwise, this String object is added to the
   * pool and a * reference to this String object is returned.
   *
   * It follows that for any two strings s and t, s.intern() == t.intern() is true if and only if s.equals(t) is true.
   *
   * All literal strings and string-valued constant expressions are * interned. String literals are defined in Section 3.10.5
   * of the Java * Language Specification Returns: a string that has the same contents * as this string, but is guaranteed to
   * be from a pool of unique * strings.
   *
   * Side Effect: from the description, we can see, it is tricky to know the side effect of this native method. Take a
   * conservative way to handle this.
   *
   * It may be @return = this; pool = this;
   *
   * why should we care about String in points-to analysis?
   *
   * public native java.lang.String intern();
   */
  public void java_lang_String_intern(SootMethod method, ReferenceVariable thisVar, ReferenceVariable returnVar,
      ReferenceVariable params[]) {
    helper.assignObjectTo(returnVar, Environment.v().getStringObject());
  }
}