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/*
* Copyright (C) 2003, 2008 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#ifndef ScopeChain_h
#define ScopeChain_h
#include <wtf/Assertions.h>
namespace JSC {
class JSGlobalData;
class JSGlobalObject;
class JSObject;
class ScopeChainIterator;
class ScopeChainNode {
public:
ScopeChainNode(ScopeChainNode* next, JSObject* object, JSGlobalData* globalData, JSObject* globalThis)
: next(next)
, object(object)
, globalData(globalData)
, globalThis(globalThis)
, refCount(1)
{
ASSERT(globalData);
}
#ifndef NDEBUG
// Due to the number of subtle and timing dependent bugs that have occurred due
// to deleted but still "valid" ScopeChainNodes we now deliberately clobber the
// contents in debug builds.
~ScopeChainNode()
{
next = 0;
object = 0;
globalData = 0;
globalThis = 0;
}
#endif
ScopeChainNode* next;
JSObject* object;
JSGlobalData* globalData;
JSObject* globalThis;
int refCount;
void deref() { ASSERT(refCount); if (--refCount == 0) { release();} }
void ref() { ASSERT(refCount); ++refCount; }
void release();
// Before calling "push" on a bare ScopeChainNode, a client should
// logically "copy" the node. Later, the client can "deref" the head
// of its chain of ScopeChainNodes to reclaim all the nodes it added
// after the logical copy, leaving nodes added before the logical copy
// (nodes shared with other clients) untouched.
ScopeChainNode* copy()
{
ref();
return this;
}
ScopeChainNode* push(JSObject*);
ScopeChainNode* pop();
ScopeChainIterator begin() const;
ScopeChainIterator end() const;
JSGlobalObject* globalObject() const; // defined in JSGlobalObject.h
JSObject* globalThisObject() const { return globalThis; }
#ifndef NDEBUG
void print() const;
#endif
};
inline ScopeChainNode* ScopeChainNode::push(JSObject* o)
{
ASSERT(o);
return new ScopeChainNode(this, o, globalData, globalThis);
}
inline ScopeChainNode* ScopeChainNode::pop()
{
ASSERT(next);
ScopeChainNode* result = next;
if (--refCount != 0)
++result->refCount;
else
delete this;
return result;
}
inline void ScopeChainNode::release()
{
// This function is only called by deref(),
// Deref ensures these conditions are true.
ASSERT(refCount == 0);
ScopeChainNode* n = this;
do {
ScopeChainNode* next = n->next;
delete n;
n = next;
} while (n && --n->refCount == 0);
}
class ScopeChainIterator {
public:
ScopeChainIterator(const ScopeChainNode* node)
: m_node(node)
{
}
JSObject* const & operator*() const { return m_node->object; }
JSObject* const * operator->() const { return &(operator*()); }
ScopeChainIterator& operator++() { m_node = m_node->next; return *this; }
// postfix ++ intentionally omitted
bool operator==(const ScopeChainIterator& other) const { return m_node == other.m_node; }
bool operator!=(const ScopeChainIterator& other) const { return m_node != other.m_node; }
private:
const ScopeChainNode* m_node;
};
inline ScopeChainIterator ScopeChainNode::begin() const
{
return ScopeChainIterator(this);
}
inline ScopeChainIterator ScopeChainNode::end() const
{
return ScopeChainIterator(0);
}
class NoScopeChain {};
class ScopeChain {
friend class JIT;
public:
ScopeChain(NoScopeChain)
: m_node(0)
{
}
ScopeChain(JSObject* o, JSGlobalData* globalData, JSObject* globalThis)
: m_node(new ScopeChainNode(0, o, globalData, globalThis))
{
}
ScopeChain(const ScopeChain& c)
: m_node(c.m_node->copy())
{
}
ScopeChain& operator=(const ScopeChain& c);
explicit ScopeChain(ScopeChainNode* node)
: m_node(node->copy())
{
}
~ScopeChain()
{
if (m_node)
m_node->deref();
#ifndef NDEBUG
m_node = 0;
#endif
}
void swap(ScopeChain&);
ScopeChainNode* node() const { return m_node; }
JSObject* top() const { return m_node->object; }
ScopeChainIterator begin() const { return m_node->begin(); }
ScopeChainIterator end() const { return m_node->end(); }
void push(JSObject* o) { m_node = m_node->push(o); }
void pop() { m_node = m_node->pop(); }
void clear() { m_node->deref(); m_node = 0; }
JSGlobalObject* globalObject() const { return m_node->globalObject(); }
void mark() const;
// Caution: this should only be used if the codeblock this is being used
// with needs a full scope chain, otherwise this returns the depth of
// the preceeding call frame
//
// Returns the depth of the current call frame's scope chain
int localDepth() const;
#ifndef NDEBUG
void print() const { m_node->print(); }
#endif
private:
ScopeChainNode* m_node;
};
inline void ScopeChain::swap(ScopeChain& o)
{
ScopeChainNode* tmp = m_node;
m_node = o.m_node;
o.m_node = tmp;
}
inline ScopeChain& ScopeChain::operator=(const ScopeChain& c)
{
ScopeChain tmp(c);
swap(tmp);
return *this;
}
} // namespace JSC
#endif // ScopeChain_h
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