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      1 // Copyright (c) 2006, Google Inc.
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are
      6 // met:
      7 //
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      9 // notice, this list of conditions and the following disclaimer.
     10 //     * Redistributions in binary form must reproduce the above
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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>
     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>
     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>
    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>
    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