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// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_ID_MAP_H__
#define BASE_ID_MAP_H__
#include "base/basictypes.h"
#include "base/hash_tables.h"
#include "base/logging.h"
// This object maintains a list of IDs that can be quickly converted to
// pointers to objects. It is implemented as a hash table, optimized for
// relatively small data sets (in the common case, there will be exactly one
// item in the list).
//
// Items can be inserted into the container with arbitrary ID, but the caller
// must ensure they are unique. Inserting IDs and relying on automatically
// generated ones is not allowed because they can collide.
template<class T>
class IDMap {
private:
typedef base::hash_map<int32, T*> HashTable;
typedef typename HashTable::iterator iterator;
public:
// support const iterators over the items
// Note, use iterator->first to get the ID, iterator->second to get the T*
typedef typename HashTable::const_iterator const_iterator;
IDMap() : next_id_(1) {
}
IDMap(const IDMap& other) : next_id_(other.next_id_),
data_(other.data_) {
}
const_iterator begin() const {
return data_.begin();
}
const_iterator end() const {
return data_.end();
}
// Adds a view with an automatically generated unique ID. See AddWithID.
int32 Add(T* data) {
int32 this_id = next_id_;
DCHECK(data_.find(this_id) == data_.end()) << "Inserting duplicate item";
data_[this_id] = data;
next_id_++;
return this_id;
}
// Adds a new data member with the specified ID. The ID must not be in
// the list. The caller either must generate all unique IDs itself and use
// this function, or allow this object to generate IDs and call Add. These
// two methods may not be mixed, or duplicate IDs may be generated
void AddWithID(T* data, int32 id) {
DCHECK(data_.find(id) == data_.end()) << "Inserting duplicate item";
data_[id] = data;
}
void Remove(int32 id) {
iterator i = data_.find(id);
if (i == data_.end()) {
NOTREACHED() << "Attempting to remove an item not in the list";
return;
}
data_.erase(i);
}
bool IsEmpty() const {
return data_.empty();
}
T* Lookup(int32 id) const {
const_iterator i = data_.find(id);
if (i == data_.end())
return NULL;
return i->second;
}
size_t size() const {
return data_.size();
}
protected:
// The next ID that we will return from Add()
int32 next_id_;
HashTable data_;
};
#endif // BASE_ID_MAP_H__
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