runtime/StringRecursionChecker.h

   1 /*
   2  *  Copyright (C) 2011 Apple Inc. All rights reserved.
   3  *
   4  *  This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU Lesser General Public
   6  *  License as published by the Free Software Foundation; either
   7  *  version 2 of the License, or (at your option) any later version.
   8  *
   9  *  This library is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  *  Lesser General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU Lesser General Public
  15  *  License along with this library; if not, write to the Free Software
  16  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  17  *
  18  */
  19
  20 #ifndef StringRecursionChecker_h
  21 #define StringRecursionChecker_h
  22
  23 #include "Interpreter.h"
  24
  25 namespace JSC {
  26
  27 class StringRecursionChecker {
  28     WTF_MAKE_NONCOPYABLE(StringRecursionChecker);
  29
  30 public:
  31     StringRecursionChecker(ExecState*, JSObject* thisObject);
  32     ~StringRecursionChecker();
  33
  34     JSValue earlyReturnValue() const; // 0 if everything is OK, value to return for failure cases
  35
  36 private:
  37     JSValue throwStackOverflowError();
  38     JSValue emptyString();
  39     JSValue performCheck();
  40
  41     ExecState* m_exec;
  42     JSObject* m_thisObject;
  43     JSValue m_earlyReturnValue;
  44 };
  45
  46 inline JSValue StringRecursionChecker::performCheck()
  47 {
  48     int size = m_exec->globalData().stringRecursionCheckVisitedObjects.size();
  49     if (size >= MaxSmallThreadReentryDepth && size >= m_exec->globalData().maxReentryDepth)
  50         return throwStackOverflowError();
  51     bool alreadyVisited = !m_exec->globalData().stringRecursionCheckVisitedObjects.add(m_thisObject).isNewEntry;
  52     if (alreadyVisited)
  53         return emptyString(); // Return empty string to avoid infinite recursion.
  54     return JSValue(); // Indicate success.
  55 }
  56
  57 inline StringRecursionChecker::StringRecursionChecker(ExecState* exec, JSObject* thisObject)
  58     : m_exec(exec)
  59     , m_thisObject(thisObject)
  60     , m_earlyReturnValue(performCheck())
  61 {
  62 }
  63
  64 inline JSValue StringRecursionChecker::earlyReturnValue() const
  65 {
  66     return m_earlyReturnValue;
  67 }
  68
  69 inline StringRecursionChecker::~StringRecursionChecker()
  70 {
  71     if (m_earlyReturnValue)
  72         return;
  73     ASSERT(m_exec->globalData().stringRecursionCheckVisitedObjects.contains(m_thisObject));
  74     m_exec->globalData().stringRecursionCheckVisitedObjects.remove(m_thisObject);
  75 }
  76
  77 }
  78
  79 #endif