/thirdparty/breakpad/processor/contained_range_map-inl.h

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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
 46namespace google_breakpad {
 47
 48
 49template<typename AddressType, typename EntryType>
 50ContainedRangeMap<AddressType, EntryType>::~ContainedRangeMap() {
 51  // Clear frees the children pointed to by the map, and frees the map itself.
 52  Clear();
 53}
 54
 55
 56template<typename AddressType, typename EntryType>
 57bool 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
150template<typename AddressType, typename EntryType>
151bool 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
181template<typename AddressType, typename EntryType>
182void 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__