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#ifndef _GEOMETRY_CACHE_H
#define _GEOMETRY_CACHE_H
// A small class to map from ID -> geometry, with
// a bounded size and LRU-ish behaviour.
//
// Not safe for multi-threaded use!
#include "coordinates.h"
#include <memory>
#define NUM_BUCKETS 256
// Keep bucket size small so linear search is fast
#define BUCKET_SIZE 32
template <class T>
class GeometryCache {
public:
GeometryCache():
offsets(NUM_BUCKETS),
ids(NUM_BUCKETS * BUCKET_SIZE),
geometries(NUM_BUCKETS * BUCKET_SIZE) {}
T* get(NodeID objectID) {
const size_t bucket = objectID % NUM_BUCKETS;
for (size_t i = bucket * BUCKET_SIZE; i < (bucket + 1) * BUCKET_SIZE; i++)
if (ids[i] == objectID)
return geometries[i].get();
return nullptr;
}
void add(NodeID objectID, std::shared_ptr<T> geom) {
const size_t bucket = objectID % NUM_BUCKETS;
size_t offset = bucket * BUCKET_SIZE + offsets[bucket];
geometries[offset] = geom;
ids[offset] = objectID;
offsets[bucket]++;
if (offsets[bucket] == BUCKET_SIZE)
offsets[bucket] = 0;
}
private:
std::vector<uint8_t> offsets;
std::vector<NodeID> ids;
// CONSIDER: we could use a raw pointer - getOrBuildLinestring controls the lifetime
std::vector<std::shared_ptr<Linestring>> geometries;
};
#endif
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