/thirdparty/breakpad/processor/contained_range_map.h

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 29
 30// contained_range_map.h: Hierarchically-organized range maps.
 31//
 32// A contained range map is similar to a standard range map, except it allows
 33// objects to be organized hierarchically.  A contained range map allows
 34// objects to contain other objects.  It is not sensitive to the order that
 35// objects are added to the map: larger, more general, containing objects
 36// may be added either before or after smaller, more specific, contained
 37// ones.
 38//
 39// Contained range maps guarantee that each object may only contain smaller
 40// objects than itself, and that a parent object may only contain child
 41// objects located entirely within the parent's address space.  Attempts
 42// to introduce objects (via StoreRange) that violate these rules will fail.
 43// Retrieval (via RetrieveRange) always returns the most specific (smallest)
 44// object that contains the address being queried.  Note that while it is
 45// not possible to insert two objects into a map that have exactly the same
 46// geometry (base address and size), it is possible to completely mask a
 47// larger object by inserting smaller objects that entirely fill the larger
 48// object's address space.
 49//
 50// Internally, contained range maps are implemented as a tree.  Each tree
 51// node except for the root node describes an object in the map.  Each node
 52// maintains its list of children in a map similar to a standard range map,
 53// keyed by the highest address that each child occupies.  Each node's
 54// children occupy address ranges entirely within the node.  The root node
 55// is the only node directly accessible to the user, and represents the
 56// entire address space.
 57//
 58// Author: Mark Mentovai
 59
 60#ifndef PROCESSOR_CONTAINED_RANGE_MAP_H__
 61#define PROCESSOR_CONTAINED_RANGE_MAP_H__
 62
 63
 64#include <map>
 65
 66
 67namespace google_breakpad {
 68
 69// Forward declarations (for later friend declarations of specialized template).
 70template<class, class> class ContainedRangeMapSerializer;
 71
 72template<typename AddressType, typename EntryType>
 73class ContainedRangeMap {
 74 public:
 75  // The default constructor creates a ContainedRangeMap with no geometry
 76  // and no entry, and as such is only suitable for the root node of a
 77  // ContainedRangeMap tree.
 78  ContainedRangeMap() : base_(), entry_(), map_(NULL) {}
 79
 80  ~ContainedRangeMap();
 81
 82  // Inserts a range into the map.  If the new range is encompassed by
 83  // an existing child range, the new range is passed into the child range's
 84  // StoreRange method.  If the new range encompasses any existing child
 85  // ranges, those child ranges are moved to the new range, becoming
 86  // grandchildren of this ContainedRangeMap.  Returns false for a
 87  // parameter error, or if the ContainedRangeMap hierarchy guarantees
 88  // would be violated.
 89  bool StoreRange(const AddressType &base,
 90                  const AddressType &size,
 91                  const EntryType &entry);
 92
 93  // Retrieves the most specific (smallest) descendant range encompassing
 94  // the specified address.  This method will only return entries held by
 95  // child ranges, and not the entry contained by |this|.  This is necessary
 96  // to support a sparsely-populated root range.  If no descendant range
 97  // encompasses the address, returns false.
 98  bool RetrieveRange(const AddressType &address, EntryType *entry) const;
 99
100  // Removes all children.  Note that Clear only removes descendants,
101  // leaving the node on which it is called intact.  Because the only
102  // meaningful things contained by a root node are descendants, this
103  // is sufficient to restore an entire ContainedRangeMap to its initial
104  // empty state when called on the root node.
105  void Clear();
106
107 private:
108  friend class ContainedRangeMapSerializer<AddressType, EntryType>;
109  friend class ModuleComparer;
110
111  // AddressToRangeMap stores pointers.  This makes reparenting simpler in
112  // StoreRange, because it doesn't need to copy entire objects.
113  typedef std::map<AddressType, ContainedRangeMap *> AddressToRangeMap;
114  typedef typename AddressToRangeMap::const_iterator MapConstIterator;
115  typedef typename AddressToRangeMap::iterator MapIterator;
116  typedef typename AddressToRangeMap::value_type MapValue;
117
118  // Creates a new ContainedRangeMap with the specified base address, entry,
119  // and initial child map, which may be NULL.  This is only used internally
120  // by ContainedRangeMap when it creates a new child.
121  ContainedRangeMap(const AddressType &base, const EntryType &entry,
122                    AddressToRangeMap *map)
123      : base_(base), entry_(entry), map_(map) {}
124
125  // The base address of this range.  The high address does not need to
126  // be stored, because it is used as the key to an object in its parent's
127  // map, and all ContainedRangeMaps except for the root range are contained
128  // within maps.  The root range does not actually contain an entry, so its
129  // base_ field is meaningless, and the fact that it has no parent and thus
130  // no key is unimportant.  For this reason, the base_ field should only be
131  // is accessed on child ContainedRangeMap objects, and never on |this|.
132  const AddressType base_;
133
134  // The entry corresponding to this range.  The root range does not
135  // actually contain an entry, so its entry_ field is meaningless.  For
136  // this reason, the entry_ field should only be accessed on child
137  // ContainedRangeMap objects, and never on |this|.
138  const EntryType entry_;
139
140  // The map containing child ranges, keyed by each child range's high
141  // address.  This is a pointer to avoid allocating map structures for
142  // leaf nodes, where they are not needed.
143  AddressToRangeMap *map_;
144};
145
146
147}  // namespace google_breakpad
148
149
150#endif  // PROCESSOR_CONTAINED_RANGE_MAP_H__