crow

Utility library

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Resource Handle

#include "crow/resource.hpp"
namespace Crow;

Resource Handle

Supporting types

template <typename T, typename U>
concept ResourceDeleter =
    std::is_default_constructible_v<T> && std::invocable<T, U>;

Concept representing a type that can be used as a deleter to free a resource.

Resource class

template <std::regular T, ResourceDeleter<T> Del, T Null = T()>
    class Resource;

This is a wrapper class for resource handles (e.g. file handles). The destructor will release the resource by calling the deleter function. The null value represents a null resource handle; this defaults to zero or a null pointer, but a different value can be supplied (e.g. -1 for a null Unix file descriptor).

Behaviour is undefined if the deleter throws an exception.

using Resource::value_type = T;
using Resource::deleter_type = Del;

Member types.

static constexpr T Resource::null = Null;

Member constants.

constexpr Resource::Resource() noexcept;
constexpr explicit Resource::Resource(T t) noexcept;
Resource::~Resource() noexcept;
constexpr Resource::Resource(Resource&& r) noexcept;
Resource& Resource::operator=(Resource&& r) noexcept;
Resource& Resource::operator=(T t) noexcept;

Life cycle functions. Resource is movable but not copyable. The internal handle in a moved-from Resource is reset to Null. The destructor will call the deleter to release the resource if the internal handle is not equal to Null. The LHS of the move assignment operator will also be released.

The assignment operator from a T is a synonym for reset(t).

constexpr explicit Resource::operator T() const noexcept;
constexpr T Resource::get() const noexcept;

Return the internal handle.

constexpr explicit Resource::operator bool() const noexcept;

True if the handle is not equal to Null.

constexpr std::remove_pointer_t<T>& Resource::operator*() const noexcept;
constexpr std::remove_pointer_t<T>* Resource::operator->() const noexcept;

Dereference the internal handle. These are only defined if T is a pointer type.

constexpr T Resource::release() noexcept;

Returns the resource handle and sets the object’s internal handle to Null.

void Resource::reset() noexcept;

If the internal handle is not Null, this will call the deleter and then set the handle to Null.

void Resource::reset(T t) noexcept;

Replaces the current internal handle. The deleter will be called on the original handle if it is not Null.

constexpr void Resource::swap(Resource& r) noexcept;
constexpr void swap(Resource& a, Resource& b) noexcept;

Swap two resource handles.

crow

Resource Handle

Contents

Supporting types

Resource class