ObjectPool_test.cc

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#include "catch.hpp"
 
#include "ObjectPool.hh"
#include "xrange.hh"
#include <vector>
 
 
struct Tracked
{
        static inline std::vector<int> constructed;
        static inline std::vector<int> destructed;
 
        explicit Tracked(int i_) : i(i_) {
                constructed.push_back(i);
        }
        Tracked(const Tracked&) = delete;
        Tracked(Tracked&&) = delete;
        Tracked& operator=(const Tracked&) = delete;
        Tracked& operator=(Tracked&&) = delete;
        ~Tracked() {
                destructed.push_back(i);
        }
        int i;
};
 
TEST_CASE("ObjectPool")
{
        REQUIRE(Tracked::constructed.empty());
        REQUIRE(Tracked::destructed.empty());
 
        {
                ObjectPool<Tracked> pool;
                CHECK(pool.capacity() == 0); // empty pool does no memory allocation
 
                // insert '10'
                auto [idx1, ptr1] = pool.emplace(10);
                CHECK(ptr1->i == 10);
                CHECK(&pool[idx1] == ptr1);
                CHECK(Tracked::constructed == std::vector{10});
                CHECK(Tracked::destructed  == std::vector<int>{});
                CHECK(pool.capacity() == 256); // allocates in chunks of 256
 
                // insert '20'
                auto [idx2, ptr2] = pool.emplace(20);
                CHECK(ptr1->i == 10);
                CHECK(ptr2->i == 20);
                CHECK(&pool[idx1] == ptr1);
                CHECK(&pool[idx2] == ptr2);
                CHECK(Tracked::constructed == std::vector{10, 20});
                CHECK(Tracked::destructed  == std::vector<int>{});
 
                // insert '30'
                auto [idx3, ptr3] = pool.emplace(30);
                CHECK(ptr1->i == 10);
                CHECK(ptr2->i == 20);
                CHECK(ptr3->i == 30);
                CHECK(&pool[idx1] == ptr1);
                CHECK(&pool[idx2] == ptr2);
                CHECK(&pool[idx3] == ptr3);
                CHECK(Tracked::constructed == std::vector{10, 20, 30});
                CHECK(Tracked::destructed  == std::vector<int>{});
 
                // remove '20'
                pool.remove(idx2);
                CHECK(ptr1->i == 10);
                CHECK(ptr3->i == 30);
                CHECK(&pool[idx1] == ptr1);
                CHECK(&pool[idx3] == ptr3);
                CHECK(Tracked::constructed == std::vector{10, 20, 30});
                CHECK(Tracked::destructed  == std::vector{20});
 
                // insert '40'
                auto [idx4, ptr4] = pool.emplace(40);
                CHECK(idx4 == idx2); // recycled
                CHECK(ptr1->i == 10);
                CHECK(ptr3->i == 30);
                CHECK(ptr4->i == 40);
                CHECK(&pool[idx1] == ptr1);
                CHECK(&pool[idx3] == ptr3);
                CHECK(&pool[idx4] == ptr4);
                CHECK(Tracked::constructed == std::vector{10, 20, 30, 40});
                CHECK(Tracked::destructed  == std::vector{20});
                CHECK(pool.capacity() == 256);
 
                // insert a lot more (force allocating more memory in the pool)
                for (auto i : xrange(1000)) {
                        auto val = 1000 + i;
                        auto [idx, ptr] = pool.emplace(val);
                        CHECK(ptr->i == val);
                        CHECK(&pool[idx] == ptr);
                }
                CHECK(Tracked::constructed.size() == 1004);
                CHECK(Tracked::destructed == std::vector{20});
                CHECK(pool.capacity() == 1024);
        }
 
        // When 'pool' goes out of scope it does _not_ destruct the elements it
        // still contained. (But it does free the memory it used to store those
        // elements.)
        CHECK(Tracked::constructed.size() == 1004);
        CHECK(Tracked::destructed == std::vector{20});
}
 
 
// To (manually) inspect quality of generated code
#if 0
 
auto inspect_operator(ObjectPool<int>& pool, unsigned idx)
{
        return pool[idx];
}
 
auto inspect_emplace(ObjectPool<int>& pool, int val)
{
        return pool.emplace(val);
}
 
void inspect_remove(ObjectPool<int>& pool, unsigned idx)
{
        return pool.remove(idx);
}
 
#endif