/* Soot - a J*va Optimization Framework
* Copyright (C) 2003 Feng Qian
*
* This library 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 library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* Simulates the native method side effects in class java.lang.String
*
* @author Feng Qian
* @author <XXX>
*/
package soot.jimple.toolkits.pointer.nativemethods;
import soot.*;
import soot.jimple.toolkits.pointer.representations.*;
import soot.jimple.toolkits.pointer.util.*;
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());
}
}