contained_range_map.h

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// Copyright (c) 2006, Google Inc.

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// contained_range_map.h: Hierarchically-organized range maps.

//

// A contained range map is similar to a standard range map, except it allows

// objects to be organized hierarchically.  A contained range map allows

// objects to contain other objects.  It is not sensitive to the order that

// objects are added to the map: larger, more general, containing objects

// may be added either before or after smaller, more specific, contained

// ones.

//

// Contained range maps guarantee that each object may only contain smaller

// objects than itself, and that a parent object may only contain child

// objects located entirely within the parent's address space.  Attempts

// to introduce objects (via StoreRange) that violate these rules will fail.

// Retrieval (via RetrieveRange) always returns the most specific (smallest)

// object that contains the address being queried.  Note that while it is

// not possible to insert two objects into a map that have exactly the same

// geometry (base address and size), it is possible to completely mask a

// larger object by inserting smaller objects that entirely fill the larger

// object's address space.

//

// Internally, contained range maps are implemented as a tree.  Each tree

// node except for the root node describes an object in the map.  Each node

// maintains its list of children in a map similar to a standard range map,

// keyed by the highest address that each child occupies.  Each node's

// children occupy address ranges entirely within the node.  The root node

// is the only node directly accessible to the user, and represents the

// entire address space.

//

// Author: Mark Mentovai

#ifndef PROCESSOR_CONTAINED_RANGE_MAP_H__

#define PROCESSOR_CONTAINED_RANGE_MAP_H__

#include <map>

namespace google_breakpad {

// Forward declarations (for later friend declarations of specialized template).

template<class, class> class ContainedRangeMapSerializer;

template<typename AddressType, typename EntryType>

class ContainedRangeMap {

 public:

  // The default constructor creates a ContainedRangeMap with no geometry

  // and no entry, and as such is only suitable for the root node of a

  // ContainedRangeMap tree.

  ContainedRangeMap() : base_(), entry_(), map_(NULL) {}

  ~ContainedRangeMap();

  // Inserts a range into the map.  If the new range is encompassed by

  // an existing child range, the new range is passed into the child range's

  // StoreRange method.  If the new range encompasses any existing child

  // ranges, those child ranges are moved to the new range, becoming

  // grandchildren of this ContainedRangeMap.  Returns false for a

  // parameter error, or if the ContainedRangeMap hierarchy guarantees

  // would be violated.

  bool StoreRange(const AddressType &base,

                  const AddressType &size,

                  const EntryType &entry);

  // Retrieves the most specific (smallest) descendant range encompassing

  // the specified address.  This method will only return entries held by

  // child ranges, and not the entry contained by |this|.  This is necessary

  // to support a sparsely-populated root range.  If no descendant range

  // encompasses the address, returns false.

  bool RetrieveRange(const AddressType &address, EntryType *entry) const;

  // Removes all children.  Note that Clear only removes descendants,

  // leaving the node on which it is called intact.  Because the only

  // meaningful things contained by a root node are descendants, this

  // is sufficient to restore an entire ContainedRangeMap to its initial

  // empty state when called on the root node.

  void Clear();

 private:

  friend class ContainedRangeMapSerializer<AddressType, EntryType>;

  friend class ModuleComparer;

  // AddressToRangeMap stores pointers.  This makes reparenting simpler in

  // StoreRange, because it doesn't need to copy entire objects.

  typedef std::map<AddressType, ContainedRangeMap *> AddressToRangeMap;

  typedef typename AddressToRangeMap::const_iterator MapConstIterator;

  typedef typename AddressToRangeMap::iterator MapIterator;

  typedef typename AddressToRangeMap::value_type MapValue;

  // Creates a new ContainedRangeMap with the specified base address, entry,

  // and initial child map, which may be NULL.  This is only used internally

  // by ContainedRangeMap when it creates a new child.

  ContainedRangeMap(const AddressType &base, const EntryType &entry,

                    AddressToRangeMap *map)

      : base_(base), entry_(entry), map_(map) {}

  // The base address of this range.  The high address does not need to

  // be stored, because it is used as the key to an object in its parent's

  // map, and all ContainedRangeMaps except for the root range are contained

  // within maps.  The root range does not actually contain an entry, so its

  // base_ field is meaningless, and the fact that it has no parent and thus

  // no key is unimportant.  For this reason, the base_ field should only be

  // is accessed on child ContainedRangeMap objects, and never on |this|.

  const AddressType base_;

  // The entry corresponding to this range.  The root range does not

  // actually contain an entry, so its entry_ field is meaningless.  For

  // this reason, the entry_ field should only be accessed on child

  // ContainedRangeMap objects, and never on |this|.

  const EntryType entry_;

  // The map containing child ranges, keyed by each child range's high

  // address.  This is a pointer to avoid allocating map structures for

  // leaf nodes, where they are not needed.

  AddressToRangeMap *map_;

};

}  // namespace google_breakpad

#endif  // PROCESSOR_CONTAINED_RANGE_MAP_H__