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39
40//
41// W A R N I N G
42// -------------
43//
44// This file is not part of the Qt API. It exists purely as an
45// implementation detail. This header file may change from version to
46// version without notice, or even be removed.
47//
48// We mean it.
49
50#ifndef Patternist_OperandsIterator_H
51#define Patternist_OperandsIterator_H
52
53#include <QPair>
54#include <QStack>
55
56#include <private/qexpression_p.h>
57
58QT_BEGIN_NAMESPACE
59
60namespace QPatternist
61{
62 /**
63 * @short A helper class that iterates a tree of Expression instances. It
64 * is not a sub-class of QAbstractXmlForwardIterator.
65 *
66 * The OperandsIterator delivers all Expression instances that are children at any
67 * depth of the Expression passed in the constructor.
68 * The order is delivered in a defined way, from left to right and depth
69 * first.
70 *
71 * @author Frans Englich <frans.englich@nokia.com>
72 */
73 class OperandsIterator
74 {
75 /**
76 * The second value, the int, is the current position in the first.
77 */
78 typedef QPair<Expression::List, int> Level;
79
80 public:
81 enum TreatParent
82 {
83 ExcludeParent,
84 IncludeParent
85 };
86
87 /**
88 * if @p treatParent is @c IncludeParent, @p start is excluded.
89 *
90 * @p start must be a valid Expression.
91 */
92 inline OperandsIterator(const Expression::Ptr &start,
93 const TreatParent treatParent)
94 {
95 Q_ASSERT(start);
96 if(treatParent == IncludeParent)
97 {
98 Expression::List l;
99 l.append(t: start);
100 m_exprs.push(t: qMakePair(x: l, y: -1));
101 }
102
103 m_exprs.push(t: qMakePair(x: start->operands(), y: -1));
104 }
105
106 /**
107 * @short Returns the current Expression and advances the iterator.
108 *
109 * If the end has been reached, a default constructed pointer is
110 * returned.
111 *
112 * We intentionally return by reference.
113 */
114 inline Expression::Ptr next()
115 {
116 if(m_exprs.isEmpty())
117 return Expression::Ptr();
118
119 Level &lvl = m_exprs.top();
120 ++lvl.second;
121
122 if(lvl.second == lvl.first.size())
123 {
124 /* Resume iteration above us. */
125 m_exprs.pop();
126
127 if(m_exprs.isEmpty())
128 return Expression::Ptr();
129
130 while(true)
131 {
132 Level &previous = m_exprs.top();
133 ++previous.second;
134
135 if(previous.second < previous.first.count())
136 {
137 const Expression::Ptr &op = previous.first.at(i: previous.second);
138 m_exprs.push(t: qMakePair(x: op->operands(), y: -1));
139 return op;
140 }
141 else
142 {
143 // We have already reached the end of this level.
144 m_exprs.pop();
145 if(m_exprs.isEmpty())
146 return Expression::Ptr();
147 }
148 }
149 }
150 else
151 {
152 const Expression::Ptr &op = lvl.first.at(i: lvl.second);
153 m_exprs.push(t: qMakePair(x: op->operands(), y: -1));
154 return op;
155 }
156 }
157
158 /**
159 * Advances this iterator by the current expression and its operands.
160 */
161 Expression::Ptr skipOperands()
162 {
163 if(m_exprs.isEmpty())
164 return Expression::Ptr();
165
166 Level &lvl = m_exprs.top();
167 ++lvl.second;
168
169 if(lvl.second == lvl.first.size())
170 {
171 /* We've reached the end of this level, at least. */
172 m_exprs.pop();
173 }
174
175 return next();
176 }
177
178 private:
179 Q_DISABLE_COPY(OperandsIterator)
180
181 QStack<Level> m_exprs;
182 };
183}
184
185
186QT_END_NAMESPACE
187
188#endif
189

source code of qtxmlpatterns/src/xmlpatterns/expr/qoperandsiterator_p.h