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/*
* Copyright (C) 2015-2016 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef ScopedArguments_h
#define ScopedArguments_h
#include "GenericArguments.h"
#include "JSLexicalEnvironment.h"
namespace JSC {
// This is an Arguments-class object that we create when you say "arguments" inside a function,
// and one or more of the arguments may be captured in the function's activation. The function
// will copy its formally declared arguments into the activation and then create this object. This
// object will store the overflow arguments, if there are any. This object will use the symbol
// table's ScopedArgumentsTable and the activation, or its overflow storage, to handle all indexed
// lookups.
class ScopedArguments : public GenericArguments<ScopedArguments> {
private:
ScopedArguments(VM&, Structure*, unsigned totalLength);
void finishCreation(VM&, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*);
public:
// Creates an arguments object but leaves it uninitialized. This is dangerous if we GC right
// after allocation.
static ScopedArguments* createUninitialized(VM&, Structure*, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*, unsigned totalLength);
// Creates an arguments object and initializes everything to the empty value. Use this if you
// cannot guarantee that you'll immediately initialize all of the elements.
static ScopedArguments* create(VM&, Structure*, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*, unsigned totalLength);
// Creates an arguments object by copying the arguments from the stack.
static ScopedArguments* createByCopying(ExecState*, ScopedArgumentsTable*, JSLexicalEnvironment*);
// Creates an arguments object by copying the arguments from a well-defined stack location.
static ScopedArguments* createByCopyingFrom(VM&, Structure*, Register* argumentsStart, unsigned totalLength, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*);
static void visitChildren(JSCell*, SlotVisitor&);
uint32_t internalLength() const
{
return m_totalLength;
}
uint32_t length(ExecState* exec) const
{
if (UNLIKELY(m_overrodeThings))
return get(exec, exec->propertyNames().length).toUInt32(exec);
return internalLength();
}
bool canAccessIndexQuickly(uint32_t i) const
{
if (i >= m_totalLength)
return false;
unsigned namedLength = m_table->length();
if (i < namedLength)
return !!m_table->get(i);
return !!overflowStorage()[i - namedLength].get();
}
bool canAccessArgumentIndexQuicklyInDFG(uint32_t i) const
{
return canAccessIndexQuickly(i);
}
JSValue getIndexQuickly(uint32_t i) const
{
ASSERT_WITH_SECURITY_IMPLICATION(canAccessIndexQuickly(i));
unsigned namedLength = m_table->length();
if (i < namedLength)
return m_scope->variableAt(m_table->get(i)).get();
return overflowStorage()[i - namedLength].get();
}
void setIndexQuickly(VM& vm, uint32_t i, JSValue value)
{
ASSERT_WITH_SECURITY_IMPLICATION(canAccessIndexQuickly(i));
unsigned namedLength = m_table->length();
if (i < namedLength)
m_scope->variableAt(m_table->get(i)).set(vm, m_scope.get(), value);
else
overflowStorage()[i - namedLength].set(vm, this, value);
}
WriteBarrier<JSFunction>& callee()
{
return m_callee;
}
bool overrodeThings() const { return m_overrodeThings; }
void overrideThings(VM&);
void overrideThingsIfNecessary(VM&);
void overrideArgument(VM&, uint32_t index);
void copyToArguments(ExecState*, VirtualRegister firstElementDest, unsigned offset, unsigned length);
DECLARE_INFO;
static Structure* createStructure(VM&, JSGlobalObject*, JSValue prototype);
static ptrdiff_t offsetOfOverrodeThings() { return OBJECT_OFFSETOF(ScopedArguments, m_overrodeThings); }
static ptrdiff_t offsetOfTotalLength() { return OBJECT_OFFSETOF(ScopedArguments, m_totalLength); }
static ptrdiff_t offsetOfTable() { return OBJECT_OFFSETOF(ScopedArguments, m_table); }
static ptrdiff_t offsetOfScope() { return OBJECT_OFFSETOF(ScopedArguments, m_scope); }
static size_t overflowStorageOffset()
{
return WTF::roundUpToMultipleOf<sizeof(WriteBarrier<Unknown>)>(sizeof(ScopedArguments));
}
static size_t allocationSize(unsigned overflowArgumentsLength)
{
return overflowStorageOffset() + sizeof(WriteBarrier<Unknown>) * overflowArgumentsLength;
}
private:
WriteBarrier<Unknown>* overflowStorage() const
{
return bitwise_cast<WriteBarrier<Unknown>*>(
bitwise_cast<char*>(this) + overflowStorageOffset());
}
bool m_overrodeThings; // True if length, callee, and caller are fully materialized in the object.
unsigned m_totalLength; // The length of declared plus overflow arguments.
WriteBarrier<JSFunction> m_callee;
WriteBarrier<ScopedArgumentsTable> m_table;
WriteBarrier<JSLexicalEnvironment> m_scope;
};
} // namespace JSC
#endif // ScopedArguments_h
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