注意一下代码的Entry& e = _table[key];,如果key不在map中,那么该代码应该会自动分配一个key和其数据空间
osgEarthDrivers/engine_rex/TileNodeRegistry
struct RandomAccessTileMap
{
struct Entry {
osg::ref_ptr<TileNode> tile;
unsigned index;
};
typedef std::map<TileKey, Entry> Table;
void insert(const TileKey& key, TileNode* data) {
Entry& e = _table[key];
e.tile = data;
e.index = _vector.size();
_vector.push_back( &e );
}
}