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 EncodedJSValue earlyReturnValue() const; // 0 if everything is OK, value to return for failure cases
35
36 private:
37 EncodedJSValue throwStackOverflowError();
38 EncodedJSValue emptyString();
39 EncodedJSValue performCheck();
40
41 ExecState* m_exec;
42 JSObject* m_thisObject;
43 EncodedJSValue m_earlyReturnValue;
44 };
45
performCheck()46 inline EncodedJSValue 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).second;
52 if (alreadyVisited)
53 return emptyString(); // Return empty string to avoid infinite recursion.
54 return 0; // Indicate success.
55 }
56
StringRecursionChecker(ExecState * exec,JSObject * thisObject)57 inline StringRecursionChecker::StringRecursionChecker(ExecState* exec, JSObject* thisObject)
58 : m_exec(exec)
59 , m_thisObject(thisObject)
60 , m_earlyReturnValue(performCheck())
61 {
62 }
63
earlyReturnValue()64 inline EncodedJSValue StringRecursionChecker::earlyReturnValue() const
65 {
66 return m_earlyReturnValue;
67 }
68
~StringRecursionChecker()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
80