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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 | |
51 | /** |
52 | * @file |
53 | * @short This file is included by qevaluationcache_p.h. |
54 | * If you need includes in this file, put them in qevaluationcache_p.h, outside of the namespace. |
55 | */ |
56 | |
57 | template<bool IsForGlobal> |
58 | EvaluationCache<IsForGlobal>::EvaluationCache(const Expression::Ptr &op, |
59 | const VariableDeclaration::Ptr &varDecl, |
60 | const VariableSlotID aSlot) : SingleContainer(op) |
61 | , m_declaration(varDecl) |
62 | , m_varSlot(aSlot) |
63 | { |
64 | Q_ASSERT(m_declaration); |
65 | Q_ASSERT(m_varSlot > -1); |
66 | } |
67 | |
68 | template<bool IsForGlobal> |
69 | DynamicContext::Ptr EvaluationCache<IsForGlobal>::topFocusContext(const DynamicContext::Ptr &context) |
70 | { |
71 | DynamicContext::Ptr result(context); |
72 | |
73 | while(true) |
74 | { |
75 | DynamicContext::Ptr candidate(result->previousContext()); |
76 | |
77 | /* We want the top focus, not GenericDynamicContext. */ |
78 | if(candidate && candidate->focusIterator()) |
79 | result = candidate; |
80 | else |
81 | return result; |
82 | } |
83 | } |
84 | |
85 | template<bool IsForGlobal> |
86 | Item EvaluationCache<IsForGlobal>::evaluateSingleton(const DynamicContext::Ptr &context) const |
87 | { |
88 | ItemCacheCell &cell = IsForGlobal ? context->globalItemCacheCell(slot: m_varSlot) : context->itemCacheCell(slot: m_varSlot); |
89 | |
90 | if(cell.cacheState == ItemCacheCell::Full) |
91 | return cell.cachedItem; |
92 | else |
93 | { |
94 | Q_ASSERT(cell.cacheState == ItemCacheCell::Empty); |
95 | cell.cachedItem = m_operand->evaluateSingleton(context: IsForGlobal ? topFocusContext(context) : context); |
96 | cell.cacheState = ItemCacheCell::Full; |
97 | return cell.cachedItem; |
98 | } |
99 | } |
100 | |
101 | #if defined(Q_OS_IRIX) && defined(Q_CC_MIPS) |
102 | /** |
103 | * @short Compile workaround for MIPSPro on IRIX. |
104 | * |
105 | * This function is never called. |
106 | * |
107 | * It's mere presence means the MIPSPro compiler can accept some other code below. |
108 | * |
109 | * I recommend Buddism. |
110 | */ |
111 | static inline Item::Iterator::Ptr workaroundIrixMIPSPro(const ItemSequenceCacheCell &cell) |
112 | { |
113 | return Item::Iterator::Ptr(new ListIterator<Item, Item::List>(cell.cachedItems)); |
114 | } |
115 | #endif |
116 | |
117 | template<bool IsForGlobal> |
118 | Item::Iterator::Ptr EvaluationCache<IsForGlobal>::evaluateSequence(const DynamicContext::Ptr &context) const |
119 | { |
120 | ItemSequenceCacheCell::Vector &cells = IsForGlobal ? context->globalItemSequenceCacheCells(slot: m_varSlot) : context->itemSequenceCacheCells(slot: m_varSlot); |
121 | ItemSequenceCacheCell &cell = cells[m_varSlot]; |
122 | |
123 | |
124 | if(cell.inUse) |
125 | { |
126 | context->error(QtXmlPatterns::tr(sourceText: "Circularity detected" ), |
127 | ReportContext::XTDE0640, this); |
128 | } |
129 | |
130 | switch(cell.cacheState) |
131 | { |
132 | case ItemSequenceCacheCell::Full: |
133 | { |
134 | /** |
135 | * We don't use makeListIterator() here because the MIPSPro compiler can't handle it. |
136 | */ |
137 | return Item::Iterator::Ptr(new ListIterator<Item, Item::List>(cell.cachedItems)); |
138 | } |
139 | case ItemSequenceCacheCell::Empty: |
140 | { |
141 | cell.inUse = true; |
142 | cell.sourceIterator = m_operand->evaluateSequence(context: IsForGlobal ? topFocusContext(context) : context); |
143 | cell.cacheState = ItemSequenceCacheCell::PartiallyPopulated; |
144 | Q_FALLTHROUGH(); |
145 | } |
146 | case ItemSequenceCacheCell::PartiallyPopulated: |
147 | { |
148 | cell.inUse = false; |
149 | Q_ASSERT_X(cells.at(m_varSlot).sourceIterator, Q_FUNC_INFO, |
150 | "This trigger for a cache bug which hasn't yet been analyzed." ); |
151 | return Item::Iterator::Ptr(new CachingIterator(cells, m_varSlot, IsForGlobal ? topFocusContext(context) : context)); |
152 | } |
153 | default: |
154 | { |
155 | Q_ASSERT_X(false, Q_FUNC_INFO, "This path is not supposed to be run." ); |
156 | return Item::Iterator::Ptr(); |
157 | } |
158 | } |
159 | } |
160 | |
161 | template<bool IsForGlobal> |
162 | Expression::Ptr EvaluationCache<IsForGlobal>::typeCheck(const StaticContext::Ptr &context, |
163 | const SequenceType::Ptr &reqType) |
164 | { |
165 | /* It's important that we do the typeCheck() before checking for the use of local variables, |
166 | * because ExpressionVariableReference can reference an expression that is a local variable, |
167 | * so it must rewrite itself to it operand before, and it does that in EvaluationCache::typeCheck(). */ |
168 | const Expression::Ptr me(SingleContainer::typeCheck(context, reqType)); |
169 | |
170 | OperandsIterator it(me, OperandsIterator::ExcludeParent); |
171 | Expression::Ptr next(it.next()); |
172 | |
173 | /* If our operand or any sub operand gets its value from a for-loop, we cannot |
174 | * cache it since then our cache would be filled -- but not invalidated -- on the |
175 | * first for-iteration. Consider this query: |
176 | * |
177 | * <tt>for $i in expr |
178 | * let $v := $i/p |
179 | * return ($v, $v)</tt> |
180 | * |
181 | * An evaluation cache is inserted for the two operands in the return clause. However, |
182 | * $i changes for each iteration so the cache can only be active on a per-iteration basis, |
183 | * it it's possible(which it isn't). |
184 | * |
185 | * This means that for some queries we don't cache what we really should, and hence evaluate |
186 | * in a sub-optimal way, since this DependsOnLocalVariable don't communicate whether it references |
187 | * a loop that affects us. The correct fix for this would be to let ForExpression reset the |
188 | * relevant caches only, but we don't know which ones that are. */ |
189 | while(next) |
190 | { |
191 | if(next->has(prop: DependsOnLocalVariable)) |
192 | return m_operand->typeCheck(context, reqType); |
193 | |
194 | next = it.next(); |
195 | } |
196 | |
197 | return me; |
198 | } |
199 | |
200 | template<bool IsForGlobal> |
201 | Expression::Ptr EvaluationCache<IsForGlobal>::compress(const StaticContext::Ptr &context) |
202 | { |
203 | const Expression::Ptr me(SingleContainer::compress(context)); |
204 | |
205 | if(me != this) |
206 | return me; |
207 | |
208 | if(m_operand->is(i: IDRangeVariableReference)) |
209 | return m_operand; |
210 | |
211 | if(m_declaration->usedByMany()) |
212 | { |
213 | /* If it's only an atomic value an EvaluationCache is overkill. However, |
214 | * it's still needed for functions like fn:current-time() that must adhere to |
215 | * query stability. */ |
216 | const Properties props(m_operand->properties()); |
217 | |
218 | if(props.testFlag(flag: EvaluationCacheRedundant) || |
219 | ((props.testFlag(flag: IsEvaluated)) && |
220 | !props.testFlag(flag: DisableElimination) && |
221 | CommonSequenceTypes::ExactlyOneAtomicType->matches(other: m_operand->staticType()))) |
222 | { |
223 | return m_operand; |
224 | } |
225 | else |
226 | return me; |
227 | } |
228 | else |
229 | { |
230 | /* If we're only used once, there's no need for an EvaluationCache. */ |
231 | return m_operand; |
232 | } |
233 | } |
234 | |
235 | template<bool IsForGlobal> |
236 | SequenceType::Ptr EvaluationCache<IsForGlobal>::staticType() const |
237 | { |
238 | return m_operand->staticType(); |
239 | } |
240 | |
241 | template<bool IsForGlobal> |
242 | SequenceType::List EvaluationCache<IsForGlobal>::expectedOperandTypes() const |
243 | { |
244 | /* Remember that EvaluationCache::typeCheck() will be called from multiple locations, |
245 | * which potentially have different type requirements. For instance, one wants a node, |
246 | * and another requires atomization and casting. |
247 | * |
248 | * Returning ZeroOrMoreItems is safe here because staticType() returns the operand's type |
249 | * and therefore the convertors like Atomizer will be parents to us, and hence only affect |
250 | * the relevant path. |
251 | * |
252 | * ZeroOrMoreItems also make sense logically since we're actually only used where the |
253 | * variable references reference us. */ |
254 | SequenceType::List result; |
255 | result.append(t: CommonSequenceTypes::ZeroOrMoreItems); |
256 | |
257 | return result; |
258 | } |
259 | |
260 | template<bool IsForGlobal> |
261 | Expression::Properties EvaluationCache<IsForGlobal>::properties() const |
262 | { |
263 | /* We cannot return the operand's properties unconditionally, because some |
264 | * doesn't hold for this Expression. |
265 | * |
266 | * However, some of the properties must propagate through, which are the ones being OR'd here. |
267 | */ |
268 | return m_operand->properties() & (DisableElimination | IsEvaluated | DisableTypingDeduction); |
269 | } |
270 | |
271 | template<bool IsForGlobal> |
272 | ExpressionVisitorResult::Ptr |
273 | EvaluationCache<IsForGlobal>::accept(const ExpressionVisitor::Ptr &visitor) const |
274 | { |
275 | return visitor->visit(this); |
276 | } |
277 | |
278 | template<bool IsForGlobal> |
279 | const SourceLocationReflection *EvaluationCache<IsForGlobal>::actualReflection() const |
280 | { |
281 | return m_operand->actualReflection(); |
282 | } |
283 | |
284 | |