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29 
30 // contained_range_map-inl.h: Hierarchically-organized range map implementation.
31 //
32 // See contained_range_map.h for documentation.
33 //
34 // Author: Mark Mentovai
35 
36 #ifndef PROCESSOR_CONTAINED_RANGE_MAP_INL_H__
37 #define PROCESSOR_CONTAINED_RANGE_MAP_INL_H__
38 
39 #include "processor/contained_range_map.h"
40 
41 #include <assert.h>
42 
43 #include "processor/logging.h"
44 
45 
46 namespace google_breakpad {
47 
48 
49 template<typename AddressType, typename EntryType>
~ContainedRangeMap()50 ContainedRangeMap<AddressType, EntryType>::~ContainedRangeMap() {
51   // Clear frees the children pointed to by the map, and frees the map itself.
52   Clear();
53 }
54 
55 
56 template<typename AddressType, typename EntryType>
StoreRange(const AddressType & base,const AddressType & size,const EntryType & entry)57 bool ContainedRangeMap<AddressType, EntryType>::StoreRange(
58     const AddressType &base, const AddressType &size, const EntryType &entry) {
59   AddressType high = base + size - 1;
60 
61   // Check for undersize or overflow.
62   if (size <= 0 || high < base) {
63     //TODO(nealsid) We are commenting this out in order to prevent
64     // excessive logging.  We plan to move to better logging as this
65     // failure happens quite often and is expected(see comment in
66     // basic_source_line_resolver.cc:671).
67     // BPLOG(INFO) << "StoreRange failed, " << HexString(base) << "+"
68     // << HexString(size) << ", " << HexString(high);
69     return false;
70   }
71 
72   if (!map_)
73     map_ = new AddressToRangeMap();
74 
75   MapIterator iterator_base = map_->lower_bound(base);
76   MapIterator iterator_high = map_->lower_bound(high);
77   MapIterator iterator_end = map_->end();
78 
79   if (iterator_base == iterator_high && iterator_base != iterator_end &&
80       base >= iterator_base->second->base_) {
81     // The new range is entirely within an existing child range.
82 
83     // If the new range's geometry is exactly equal to an existing child
84     // range's, it violates the containment rules, and an attempt to store
85     // it must fail.  iterator_base->first contains the key, which was the
86     // containing child's high address.
87     if (iterator_base->second->base_ == base && iterator_base->first == high) {
88       // TODO(nealsid): See the TODO above on why this is commented out.
89 //       BPLOG(INFO) << "StoreRange failed, identical range is already "
90 //                      "present: " << HexString(base) << "+" << HexString(size);
91       return false;
92     }
93 
94     // Pass the new range on to the child to attempt to store.
95     return iterator_base->second->StoreRange(base, size, entry);
96   }
97 
98   // iterator_high might refer to an irrelevant range: one whose base address
99   // is higher than the new range's high address.  Set contains_high to true
100   // only if iterator_high refers to a range that is at least partially
101   // within the new range.
102   bool contains_high = iterator_high != iterator_end &&
103                        high >= iterator_high->second->base_;
104 
105   // If the new range encompasses any existing child ranges, it must do so
106   // fully.  Partial containment isn't allowed.
107   if ((iterator_base != iterator_end && base > iterator_base->second->base_) ||
108       (contains_high && high < iterator_high->first)) {
109     // TODO(mmentovai): Some symbol files will trip this check frequently
110     // on STACK lines.  Too many messages will be produced.  These are more
111     // suitable for a DEBUG channel than an INFO channel.
112     // BPLOG(INFO) << "StoreRange failed, new range partially contains "
113     //               "existing range: " << HexString(base) << "+" <<
114     //               HexString(size);
115     return false;
116   }
117 
118   // When copying and erasing contained ranges, the "end" iterator needs to
119   // point one past the last item of the range to copy.  If contains_high is
120   // false, the iterator's already in the right place; the increment is safe
121   // because contains_high can't be true if iterator_high == iterator_end.
122   if (contains_high)
123     ++iterator_high;
124 
125   // Optimization: if the iterators are equal, no child ranges would be
126   // moved.  Create the new child range with a NULL map to conserve space
127   // in leaf nodes, of which there will be many.
128   AddressToRangeMap *child_map = NULL;
129 
130   if (iterator_base != iterator_high) {
131     // The children of this range that are contained by the new range must
132     // be transferred over to the new range.  Create the new child range map
133     // and copy the pointers to range maps it should contain into it.
134     child_map = new AddressToRangeMap(iterator_base, iterator_high);
135 
136     // Remove the copied child pointers from this range's map of children.
137     map_->erase(iterator_base, iterator_high);
138   }
139 
140   // Store the new range in the map by its high address.  Any children that
141   // the new child range contains were formerly children of this range but
142   // are now this range's grandchildren.  Ownership of these is transferred
143   // to the new child range.
144   map_->insert(MapValue(high,
145                         new ContainedRangeMap(base, entry, child_map)));
146   return true;
147 }
148 
149 
150 template<typename AddressType, typename EntryType>
RetrieveRange(const AddressType & address,EntryType * entry)151 bool ContainedRangeMap<AddressType, EntryType>::RetrieveRange(
152     const AddressType &address, EntryType *entry) const {
153   BPLOG_IF(ERROR, !entry) << "ContainedRangeMap::RetrieveRange requires "
154                              "|entry|";
155   assert(entry);
156 
157   // If nothing was ever stored, then there's nothing to retrieve.
158   if (!map_)
159     return false;
160 
161   // Get an iterator to the child range whose high address is equal to or
162   // greater than the supplied address.  If the supplied address is higher
163   // than all of the high addresses in the range, then this range does not
164   // contain a child at address, so return false.  If the supplied address
165   // is lower than the base address of the child range, then it is not within
166   // the child range, so return false.
167   MapConstIterator iterator = map_->lower_bound(address);
168   if (iterator == map_->end() || address < iterator->second->base_)
169     return false;
170 
171   // The child in iterator->second contains the specified address.  Find out
172   // if it has a more-specific descendant that also contains it.  If it does,
173   // it will set |entry| appropriately.  If not, set |entry| to the child.
174   if (!iterator->second->RetrieveRange(address, entry))
175     *entry = iterator->second->entry_;
176 
177   return true;
178 }
179 
180 
181 template<typename AddressType, typename EntryType>
Clear()182 void ContainedRangeMap<AddressType, EntryType>::Clear() {
183   if (map_) {
184     MapConstIterator end = map_->end();
185     for (MapConstIterator child = map_->begin(); child != end; ++child)
186       delete child->second;
187 
188     delete map_;
189     map_ = NULL;
190   }
191 }
192 
193 
194 }  // namespace google_breakpad
195 
196 
197 #endif  // PROCESSOR_CONTAINED_RANGE_MAP_INL_H__
198