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#ifndef _LEASED_STORE_H
#define _LEASED_STORE_H
#include "tile_data.h"
// LeasedStore implements "leases" for generated geometries.
//
// When Lua code calls Layer(...), we need to store the point, linestring,
// multilinestring, polygon geometry.
//
// Previously, we had code that would lock on each insertion:
//
// lock_guard<mutex> lock(mutex);
// insert(...)
//
// Instead, store leases let each of N threads claim a range of 1/N of the IDs.
// Then each thread can insert into their own stores without taking additional
// locks.
template<typename S>
std::vector<std::pair<size_t, S*>>& getAvailableLeases(TileDataSource* source) {
throw std::runtime_error("you need to specialize this");
}
template<>
inline std::vector<std::pair<size_t, TileDataSource::point_store_t*>>& getAvailableLeases(TileDataSource* source) {
return source->availablePointStoreLeases;
}
template<>
inline std::vector<std::pair<size_t, TileDataSource::linestring_store_t*>>& getAvailableLeases(TileDataSource* source) {
return source->availableLinestringStoreLeases;
}
template<>
inline std::vector<std::pair<size_t, TileDataSource::multi_linestring_store_t*>>& getAvailableLeases(TileDataSource* source) {
return source->availableMultiLinestringStoreLeases;
}
template<>
inline std::vector<std::pair<size_t, TileDataSource::multi_polygon_store_t*>>& getAvailableLeases(TileDataSource* source) {
return source->availableMultiPolygonStoreLeases;
}
template <class T>
class LeasedStore {
std::vector<std::pair<TileDataSource*, std::pair<size_t, T*>>> leases;
public:
~LeasedStore() {
for (const auto& lease : leases) {
auto source = lease.first;
std::lock_guard<std::mutex> lock(source->storeMutex);
std::vector<std::pair<size_t, T*>>& availableLeases = getAvailableLeases<T>(source);
availableLeases.push_back(lease.second);
}
}
std::pair<size_t, T*> get(TileDataSource* source) {
for (const auto& lease : leases) {
if (lease.first == source)
return lease.second;
}
std::lock_guard<std::mutex> lock(source->storeMutex);
std::vector<std::pair<size_t, T*>>& availableLeases = getAvailableLeases<T>(source);
if (availableLeases.empty())
throw std::runtime_error("fatal: no available stores to lease");
std::pair<size_t, T*> entry = availableLeases.back();
availableLeases.pop_back();
leases.push_back(std::make_pair(source, entry));
return entry;
}
};
#endif
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