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1 /*

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 */

20 #ifndef StringRecursionChecker_h

21 #define StringRecursionChecker_h

23 #include "Interpreter.h"

24 #include <wtf/StackStats.h>

25 #include <wtf/WTFThreadData.h>

27 namespace JSC {

29 class StringRecursionChecker {

30 WTF_MAKE_NONCOPYABLE(StringRecursionChecker);

32 public:

     StringRecursionChecker(ExecState*, JSObject* thisObject);

34 ~StringRecursionChecker();

     JSValue earlyReturnValue() const; // 0 if everything is OK, value to return for failure cases

38 private:

39 JSValue throwStackOverflowError();

40 JSValue emptyString();

41 JSValue performCheck();

43 ExecState* m_exec;

44 JSObject* m_thisObject;

45 JSValue m_earlyReturnValue;

47 StackStats::CheckPoint stackCheckpoint;

48 };

 inline JSValue StringRecursionChecker::performCheck()

51 {

     VM& vm = m_exec->vm();

     if (!vm.isSafeToRecurse())

54 return throwStackOverflowError();

56 bool alreadyVisited = false;

57 if (!vm.stringRecursionCheckFirstObject)

58 vm.stringRecursionCheckFirstObject = m_thisObject;

     else if (vm.stringRecursionCheckFirstObject == m_thisObject)

60 alreadyVisited = true;

61 else

         alreadyVisited = !vm.stringRecursionCheckVisitedObjects.add(m_thisObject).isNewEntry;

64 if (alreadyVisited)

65 return emptyString(); // Return empty string to avoid infinite recursion.

66 return JSValue(); // Indicate success.

67 }

 inline StringRecursionChecker::StringRecursionChecker(ExecState* exec, JSObject* thisObject)

70 : m_exec(exec)

71 , m_thisObject(thisObject)

     , m_earlyReturnValue(performCheck())

73 {

74 }

 inline JSValue StringRecursionChecker::earlyReturnValue() const

77 {

78 return m_earlyReturnValue;

79 }

 inline StringRecursionChecker::~StringRecursionChecker()

82 {

83 if (m_earlyReturnValue)

84 return;

     VM& vm = m_exec->vm();

     if (vm.stringRecursionCheckFirstObject == m_thisObject)

88 vm.stringRecursionCheckFirstObject = nullptr;

89 else {

         ASSERT(vm.stringRecursionCheckVisitedObjects.contains(m_thisObject));

         vm.stringRecursionCheckVisitedObjects.remove(m_thisObject);

92 }

93 }

95 }

97 #endif