kjs/scope_chain.h

   1 /*
   2  *  This file is part of the KDE libraries
   3  *  Copyright (C) 2003 Apple Computer, Inc.
   4  *
   5  *  This library is free software; you can redistribute it and/or
   6  *  modify it under the terms of the GNU Library General Public
   7  *  License as published by the Free Software Foundation; either
   8  *  version 2 of the License, or (at your option) any later version.
   9  *
  10  *  This library is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *  Library General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU Library General Public License
  16  *  along with this library; see the file COPYING.LIB.  If not, write to
  17  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18  *  Boston, MA 02110-1301, USA.
  19  *
  20  */
  21
  22 #ifndef KJS_SCOPE_CHAIN_H
  23 #define KJS_SCOPE_CHAIN_H
  24
  25 #include <wtf/Assertions.h>
  26
  27 namespace KJS {
  28
  29     class JSObject;
  30     class ExecState;
  31
  32     class ScopeChainNode {
  33     public:
  34         ScopeChainNode(ScopeChainNode *n, JSObject *o)
  35             : next(n), object(o), refCount(1) { }
  36
  37         ScopeChainNode *next;
  38         JSObject *object;
  39         int refCount;
  40     };
  41
  42     class ScopeChainIterator {
  43     public:
  44         ScopeChainIterator(ScopeChainNode *node) : m_node(node) {}
  45
  46         JSObject * const & operator*() const { return m_node->object; }
  47         JSObject * const * operator->() const { return &(operator*()); }
  48
  49         ScopeChainIterator& operator++() { m_node = m_node->next; return *this; }
  50
  51         // postfix ++ intentionally omitted
  52
  53         bool operator==(const ScopeChainIterator& other) const { return m_node == other.m_node; }
  54         bool operator!=(const ScopeChainIterator& other) const { return m_node != other.m_node; }
  55
  56     private:
  57         ScopeChainNode *m_node;
  58     };
  59
  60     class ScopeChain {
  61     public:
  62         typedef ScopeChainIterator const_iterator;
  63         typedef JSObject* ValueType;
  64
  65         ScopeChain() : _node(0) { }
  66         ~ScopeChain() { deref(); }
  67
  68         ScopeChain(const ScopeChain &c) : _node(c._node)
  69             { if (_node) ++_node->refCount; }
  70         ScopeChain &operator=(const ScopeChain &);
  71
  72         bool isEmpty() const { return !_node; }
  73         JSObject *top() const { return _node->object; }
  74
  75         JSObject *bottom() const;
  76
  77         ScopeChainIterator begin() const { return ScopeChainIterator(_node); }
  78         ScopeChainIterator end() const { return ScopeChainIterator(0); }
  79
  80         void clear() { deref(); _node = 0; }
  81         void push(JSObject *);
  82         void push(const ScopeChain &);
  83         void replaceTop(JSObject*);
  84         void pop();
  85
  86         void mark();
  87
  88 #ifndef NDEBUG
  89         void print();
  90 #endif
  91
  92     private:
  93         ScopeChainNode *_node;
  94
  95         void deref() { if (_node && --_node->refCount == 0) release(); }
  96         void ref() const;
  97
  98         void release();
  99     };
 100
 101 inline void ScopeChain::ref() const
 102 {
 103     for (ScopeChainNode *n = _node; n; n = n->next) {
 104         if (n->refCount++ != 0)
 105             break;
 106     }
 107 }
 108
 109 inline ScopeChain &ScopeChain::operator=(const ScopeChain &c)
 110 {
 111     c.ref();
 112     deref();
 113     _node = c._node;
 114     return *this;
 115 }
 116
 117 inline JSObject *ScopeChain::bottom() const
 118 {
 119     ScopeChainNode *last = 0;
 120     for (ScopeChainNode *n = _node; n; n = n->next)
 121         last = n;
 122     if (!last)
 123         return 0;
 124     return last->object;
 125 }
 126
 127 inline void ScopeChain::push(JSObject *o)
 128 {
 129     ASSERT(o);
 130     _node = new ScopeChainNode(_node, o);
 131 }
 132
 133 inline void ScopeChain::replaceTop(JSObject* o)
 134 {
 135     ASSERT(o);
 136     _node->object = o;
 137 }
 138
 139 inline void ScopeChain::pop()
 140 {
 141     ScopeChainNode *oldNode = _node;
 142     ASSERT(oldNode);
 143     ScopeChainNode *newNode = oldNode->next;
 144     _node = newNode;
 145
 146     if (--oldNode->refCount != 0) {
 147         if (newNode)
 148             ++newNode->refCount;
 149     } else {
 150         delete oldNode;
 151     }
 152 }
 153
 154 } // namespace KJS
 155
 156 #endif // KJS_SCOPE_CHAIN_H