StringRecursionChecker.h [plain text]
#ifndef StringRecursionChecker_h
#define StringRecursionChecker_h
#include "Interpreter.h"
#include "VMInlines.h"
#include <wtf/StackStats.h>
#include <wtf/WTFThreadData.h>
namespace JSC {
class StringRecursionChecker {
WTF_MAKE_NONCOPYABLE(StringRecursionChecker);
public:
StringRecursionChecker(ExecState*, JSObject* thisObject);
~StringRecursionChecker();
JSValue earlyReturnValue() const;
private:
JSValue throwStackOverflowError();
JSValue emptyString();
JSValue performCheck();
ExecState* m_exec;
JSObject* m_thisObject;
JSValue m_earlyReturnValue;
StackStats::CheckPoint stackCheckpoint;
};
inline JSValue StringRecursionChecker::performCheck()
{
VM& vm = m_exec->vm();
if (UNLIKELY(!vm.isSafeToRecurseSoft()))
return throwStackOverflowError();
bool alreadyVisited = false;
if (!vm.stringRecursionCheckFirstObject)
vm.stringRecursionCheckFirstObject = m_thisObject;
else if (vm.stringRecursionCheckFirstObject == m_thisObject)
alreadyVisited = true;
else
alreadyVisited = !vm.stringRecursionCheckVisitedObjects.add(m_thisObject).isNewEntry;
if (alreadyVisited)
return emptyString(); return JSValue(); }
inline StringRecursionChecker::StringRecursionChecker(ExecState* exec, JSObject* thisObject)
: m_exec(exec)
, m_thisObject(thisObject)
, m_earlyReturnValue(performCheck())
{
}
inline JSValue StringRecursionChecker::earlyReturnValue() const
{
return m_earlyReturnValue;
}
inline StringRecursionChecker::~StringRecursionChecker()
{
if (m_earlyReturnValue)
return;
VM& vm = m_exec->vm();
if (vm.stringRecursionCheckFirstObject == m_thisObject)
vm.stringRecursionCheckFirstObject = nullptr;
else {
ASSERT(vm.stringRecursionCheckVisitedObjects.contains(m_thisObject));
vm.stringRecursionCheckVisitedObjects.remove(m_thisObject);
}
}
}
#endif