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adding support to object construction with arguments. #259

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3ebbaf2
adding support to object construction with arguments.
tinebp Oct 23, 2023
a83f06e
minor update
tinebp Oct 24, 2023
f86a0ba
fixed C++ 11 compatibility
tinebp Oct 26, 2023
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123 changes: 53 additions & 70 deletions include/marl/pool.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,10 @@ class Pool {
MARL_NO_EXPORT inline T* get();

// construct() calls the constructor on the item's data.
MARL_NO_EXPORT inline void construct();
template <typename... Args>
MARL_NO_EXPORT inline void construct(Args&&... args) {
new (&data) T(std::forward<Args>(args)...);
}

// destruct() calls the destructor on the item's data.
MARL_NO_EXPORT inline void destruct();
Expand All @@ -110,11 +113,6 @@ T* Pool<T>::Item::get() {
return reinterpret_cast<T*>(&data);
}

template <typename T>
void Pool<T>::Item::construct() {
new (&data) T;
}

template <typename T>
void Pool<T>::Item::destruct() {
get()->~T();
Expand Down Expand Up @@ -214,32 +212,64 @@ class BoundedPool : public Pool<T> {

// borrow() borrows a single item from the pool, blocking until an item is
// returned if the pool is empty.
MARL_NO_EXPORT inline Loan borrow() const;
template <typename... Args>
MARL_NO_EXPORT inline Loan borrow(Args&&... args) const {
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@ben-clayton ben-clayton Oct 26, 2023 •
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Any reason you've inlined these methods into the class? Marl tries to keep the implementations out of the class, so the public interface is easily human parsable. I'd prefer it if these were put back where they were.

marl::lock lock(storage->mutex);
storage->returned.wait(lock, [&] { return storage->free != nullptr; });
auto item = storage->free;
storage->free = storage->free->next;
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->construct(std::forward<Args>(args)...);
}
return Loan(item, storage);
}

// borrow() borrows count items from the pool, blocking until there are at
// borrowList() borrows count items from the pool, blocking until there are at
// least count items in the pool. The function f() is called with each
// borrowed item.
// F must be a function with the signature: void(T&&)
template <typename F>
MARL_NO_EXPORT inline void borrow(size_t count, const F& f) const;
template <typename F, typename... Args>
MARL_NO_EXPORT inline void borrowList(size_t count, const F& f, Args&&... args) const {
marl::lock lock(storage->mutex);
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Please also add the static_assert here.

for (size_t i = 0; i < count; i++) {
storage->returned.wait(lock, [&] { return storage->free != nullptr; });
auto item = storage->free;
storage->free = storage->free->next;
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->construct(std::forward<Args>(args)...);
}
f(std::move(Loan(item, storage)));
}
}

// tryBorrow() attempts to borrow a single item from the pool without
// blocking.
// The boolean of the returned pair is true on success, or false if the pool
// is empty.
MARL_NO_EXPORT inline std::pair<Loan, bool> tryBorrow() const;
template <typename... Args>
MARL_NO_EXPORT inline std::pair<Loan, bool> tryBorrow(Args&&... args) const {
Item* item = nullptr;
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And here

{
marl::lock lock(storage->mutex);
if (storage->free == nullptr) {
return std::make_pair(Loan(), false);
}
item = storage->free;
storage->free = storage->free->next;
item->pool = this;
}
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->construct(std::forward<Args>(args)...);
}
return std::make_pair(Loan(item, storage), true);
}

private:
class Storage : public Pool<T>::Storage {
public:
MARL_NO_EXPORT inline Storage(Allocator* allocator);
MARL_NO_EXPORT inline ~Storage();
MARL_NO_EXPORT inline void return_(Item*) override;
// We cannot copy this as the Item pointers would be shared and
// deleted at a wrong point. We cannot move this because we return
// pointers into items[N].
MARL_NO_EXPORT inline Storage(const Storage&) = delete;
MARL_NO_EXPORT inline Storage& operator=(const Storage&) = delete;

Item items[N];
marl::mutex mutex;
Expand All @@ -253,7 +283,7 @@ template <typename T, int N, PoolPolicy POLICY>
BoundedPool<T, N, POLICY>::Storage::Storage(Allocator* allocator)
: returned(allocator) {
for (int i = 0; i < N; i++) {
if (POLICY == PoolPolicy::Preserve) {
if constexpr (POLICY == PoolPolicy::Preserve) {
items[i].construct();
}
items[i].next = this->free;
Expand All @@ -263,7 +293,7 @@ BoundedPool<T, N, POLICY>::Storage::Storage(Allocator* allocator)

template <typename T, int N, PoolPolicy POLICY>
BoundedPool<T, N, POLICY>::Storage::~Storage() {
if (POLICY == PoolPolicy::Preserve) {
if constexpr (POLICY == PoolPolicy::Preserve) {
for (int i = 0; i < N; i++) {
items[i].destruct();
}
Expand All @@ -275,51 +305,9 @@ BoundedPool<T, N, POLICY>::BoundedPool(
Allocator* allocator /* = Allocator::Default */)
: storage(allocator->make_shared<Storage>(allocator)) {}

template <typename T, int N, PoolPolicy POLICY>
typename BoundedPool<T, N, POLICY>::Loan BoundedPool<T, N, POLICY>::borrow()
const {
Loan out;
borrow(1, [&](Loan&& loan) { out = std::move(loan); });
return out;
}

template <typename T, int N, PoolPolicy POLICY>
template <typename F>
void BoundedPool<T, N, POLICY>::borrow(size_t n, const F& f) const {
marl::lock lock(storage->mutex);
for (size_t i = 0; i < n; i++) {
storage->returned.wait(lock, [&] { return storage->free != nullptr; });
auto item = storage->free;
storage->free = storage->free->next;
if (POLICY == PoolPolicy::Reconstruct) {
item->construct();
}
f(std::move(Loan(item, storage)));
}
}

template <typename T, int N, PoolPolicy POLICY>
std::pair<typename BoundedPool<T, N, POLICY>::Loan, bool>
BoundedPool<T, N, POLICY>::tryBorrow() const {
Item* item = nullptr;
{
marl::lock lock(storage->mutex);
if (storage->free == nullptr) {
return std::make_pair(Loan(), false);
}
item = storage->free;
storage->free = storage->free->next;
item->pool = this;
}
if (POLICY == PoolPolicy::Reconstruct) {
item->construct();
}
return std::make_pair(Loan(item, storage), true);
}

template <typename T, int N, PoolPolicy POLICY>
void BoundedPool<T, N, POLICY>::Storage::return_(Item* item) {
if (POLICY == PoolPolicy::Reconstruct) {
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->destruct();
}
{
Expand Down Expand Up @@ -366,11 +354,6 @@ class UnboundedPool : public Pool<T> {
MARL_NO_EXPORT inline Storage(Allocator* allocator);
MARL_NO_EXPORT inline ~Storage();
MARL_NO_EXPORT inline void return_(Item*) override;
// We cannot copy this as the Item pointers would be shared and
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While I see you've moved this up to Storage, I think it would be generally safer if this remained here as well. Please revert.

// deleted at a wrong point. We could move this but would have to take
// extra care no Item pointers are left in the moved-out object.
MARL_NO_EXPORT inline Storage(const Storage&) = delete;
MARL_NO_EXPORT inline Storage& operator=(const Storage&) = delete;

Allocator* allocator;
marl::mutex mutex;
Expand All @@ -389,7 +372,7 @@ UnboundedPool<T, POLICY>::Storage::Storage(Allocator* allocator)
template <typename T, PoolPolicy POLICY>
UnboundedPool<T, POLICY>::Storage::~Storage() {
for (auto item : items) {
if (POLICY == PoolPolicy::Preserve) {
if constexpr (POLICY == PoolPolicy::Preserve) {
item->destruct();
}
allocator->destroy(item);
Expand Down Expand Up @@ -418,7 +401,7 @@ inline void UnboundedPool<T, POLICY>::borrow(size_t n, const F& f) const {
auto count = std::max<size_t>(storage->items.size(), 32);
for (size_t j = 0; j < count; j++) {
auto item = allocator->create<Item>();
if (POLICY == PoolPolicy::Preserve) {
if constexpr (POLICY == PoolPolicy::Preserve) {
item->construct();
}
storage->items.push_back(item);
Expand All @@ -429,7 +412,7 @@ inline void UnboundedPool<T, POLICY>::borrow(size_t n, const F& f) const {

auto item = storage->free;
storage->free = storage->free->next;
if (POLICY == PoolPolicy::Reconstruct) {
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->construct();
}
f(std::move(Loan(item, storage)));
Expand All @@ -438,7 +421,7 @@ inline void UnboundedPool<T, POLICY>::borrow(size_t n, const F& f) const {

template <typename T, PoolPolicy POLICY>
void UnboundedPool<T, POLICY>::Storage::return_(Item* item) {
if (POLICY == PoolPolicy::Reconstruct) {
if constexpr (POLICY == PoolPolicy::Reconstruct) {
item->destruct();
}
marl::lock lock(mutex);
Expand Down