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// Copyright (C) 2006 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// 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_airbag {
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, or if there is a parameter error, 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:
// 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_airbag
#endif // PROCESSOR_CONTAINED_RANGE_MAP_H__
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