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Class Template resource_pool<T>

Defined in header <siddiqsoft/arrp.hpp> / <siddiqsoft/private/resource_pool.hpp>.

namespace siddiqsoft::arrp {
    template <NonNumericMoveConstructible T>
    class resource_pool;
}

resource_pool<T> is a thread-safe, non-copyable, non-movable class template that manages a pool of moveable resource instances of type T.

Member Functions

Constructors & Destructor

resource_pool(
    uint8_t init_capacity = resource_pool_limits::DefaultCapacity,
    std::function<void(T&)>&& on_shutdown_callback = {}
);

resource_pool(
    std::function<void(T&)>&& on_shutdown_callback
);
  • init_capacity: Initial capacity guidance. Clamped internally to [resource_pool_limits::MinimumCapacity, resource_pool_limits::MaxCapacity] (1 to 255).
  • on_shutdown_callback: Optional cleanup callback executed for every available resource during clear() or pool destruction. The callback executes under pool synchronization lock and must not call pool methods.

Borrowing Methods

try_borrow

resource_guard<T> try_borrow(std::chrono::nanoseconds timeout = {});

Borrows the next available resource in FIFO order.

  • Parameters: timeout - Duration to wait if no resource is available. A zero duration (0ns, default) returns immediately without blocking.
  • Return Value: A resource_guard<T>. If borrowing succeeded, operator bool() is true. If exhausted/timed out, returns an invalid guard where .error() is pool_error::NoMoreResources or pool_error::Timeout.

try_borrow_create

resource_guard<T> try_borrow_create(std::chrono::nanoseconds timeout = {});

Borrows an available resource from the pool, or invokes the registered factory callback if no resource is available after the timeout.

  • Parameters: timeout - Duration to wait before invoking the factory.
  • Return Value: A valid resource_guard<T> containing a borrowed or factory-created resource, or an invalid guard if no factory callback was set or shutdown was initiated.

Configuration & Modification

set_factory_callback

template <class F>
void set_factory_callback(F&& f);

Registers a factory callback used by try_borrow_create().

  • Parameters: f - Callable taking no parameters and returning T or resource_guard<T>.

seed

template <class... Args>
pool_error seed(Args&&... args);

pool_error seed(T&& item);

Adds a new resource to the available pool.

  • In-place construction: Constructs T(std::forward<Args>(args)...) directly in pool storage.
  • Move-seeding: Moves an existing instance of T into pool storage.
  • Return Value: pool_error::Ok on success, or pool_error::ShutdownInitiated if the pool is shutting down.

clear

pool_error clear();

Removes and destroys all resources currently available (idle) in the pool. If a shutdown callback was provided, it is invoked for each removed resource.

  • Return Value: pool_error::Ok.

Inspection & Metrics

size

size_t size() const noexcept;

Returns the current count of available (idle) resources in the pool.

to_json

nlohmann::json to_json() const;

Returns a JSON object containing pool metrics (capacity, size, borrows, returns, abandons, loans, etc.). Only compiled when nlohmann/json.hpp is included prior to arrp.hpp.