kcenon::thread::result< T > Class Template Reference

A template class representing either a value or an error. More...

#include <error_handling.h>

Collaboration diagram for kcenon::thread::result< T >:

Public Types
using	value_type = T
using	error_type = error

Public Member Functions
	result (T value)
	Constructs a result with a value.
	result (error err)
	Constructs a result with an error.
	operator bool () const noexcept
	Checks if the result contains a value.
bool	has_value () const noexcept
	Checks if the result contains a value.
bool	is_ok () const noexcept
	Checks if the result is successful.
bool	is_error () const noexcept
	Checks if the result contains an error.
T &	value () &
	Gets the value.
const T &	value () const &
	Gets the value.
T &&	value () &&
	Gets the value.
error &	get_error () &
	Gets the error.
const error &	get_error () const &
	Gets the error.
error &&	get_error () &&
	Gets the error.
template<typename U >
T	value_or (U &&default_value) const &
	Gets the value or a default.
template<typename U >
T	value_or (U &&default_value) &&
	Gets the value or a default.
T	value_or_throw () const &
	Gets the value or throws an exception.
T	value_or_throw () &&
	Gets the value or throws an exception.
template<typename Fn >
auto	map (Fn &&fn) const -> result< std::invoke_result_t< Fn, const T & > >
	Maps the result to another type using a function.
template<typename Fn >
auto	and_then (Fn &&fn) const -> std::invoke_result_t< Fn, const T & >
	Maps the result to another type using a function that returns a result.

Private Attributes
bool	has_value_ = false
T	value_ {}
error	error_ {error_code::success, ""}

Detailed Description

template<typename T>
class kcenon::thread::result< T >

A template class representing either a value or an error.

This class is similar to std::expected from C++23, but can be used with C++20. It holds either a value of type T or an error.

Examples

adaptive_queue_sample.cpp, composition_example.cpp, crash_protection/main.cpp, hazard_pointer_sample.cpp, minimal_thread_pool.cpp, mpmc_queue_sample.cpp, multi_process_monitoring_integration.cpp, queue_factory_sample.cpp, thread_pool_sample.cpp, and typed_job_queue_sample.cpp.

Definition at line 252 of file error_handling.h.

Member Typedef Documentation

error_type

template<typename T >

using kcenon::thread::result< T >::error_type = error

Definition at line 255 of file error_handling.h.

value_type

template<typename T >

using kcenon::thread::result< T >::value_type = T

Definition at line 254 of file error_handling.h.

Constructor & Destructor Documentation

result() [1/2]

template<typename T >

kcenon::thread::result< T >::result ( T value )

inline

Constructs a result with a value.

Parameters

value

The value to store

Definition at line 261 of file error_handling.h.

: has_value_(true), value_(std::move(value)), error_(error_code::success, "") {}

result() [2/2]

template<typename T >

kcenon::thread::result< T >::result ( error err )

inline

Constructs a result with an error.

Parameters

err	The error to store

Definition at line 267 of file error_handling.h.

: has_value_(false), error_(std::move(err)) {}

Member Function Documentation

and_then()

template<typename T >

template<typename Fn >

auto kcenon::thread::result< T >::and_then ( Fn && fn ) const -> std::invoke_result_t<Fn, const T&>

inlinenodiscard

Maps the result to another type using a function that returns a result.

Parameters

fn	The function to apply to the value

Returns

A new result with the mapped value or the original error

Definition at line 446 of file error_handling.h.

                                                                                   {
        using ResultType = std::invoke_result_t<Fn, const T&>;
        static_assert(std::is_same_v<typename ResultType::error_type, error>, "Function must return a result with the same error type");
        
        if (has_value_) {
            return std::invoke(std::forward<Fn>(fn), value_);
        }
        return ResultType(error_);
    }

References kcenon::thread::result< T >::error_, kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

get_error() [1/3]

template<typename T >

error & kcenon::thread::result< T >::get_error ( ) &

inlinenodiscard

Gets the error.

Returns

A reference to the contained error

Exceptions

std::runtime_error

if the result contains a value

Definition at line 344 of file error_handling.h.

                                       {
        if (has_value_) {
            throw std::runtime_error("Cannot get error from successful result");
        }
        return error_;
    }

References kcenon::thread::result< T >::error_, and kcenon::thread::result< T >::has_value_.

Referenced by kcenon::thread::typed_thread_pool_builder< job_type >::build(), kcenon::thread::result_to_optional_error(), and kcenon::thread::result_to_pair().

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get_error() [2/3]

template<typename T >

error && kcenon::thread::result< T >::get_error ( ) &&

inlinenodiscard

Gets the error.

Returns

An rvalue reference to the contained error

Exceptions

std::runtime_error

if the result contains a value

Definition at line 368 of file error_handling.h.

                                         {
        if (has_value_) {
            throw std::runtime_error("Cannot get error from successful result");
        }
        return std::move(error_);
    }

References kcenon::thread::result< T >::error_, and kcenon::thread::result< T >::has_value_.

get_error() [3/3]

template<typename T >

const error & kcenon::thread::result< T >::get_error ( ) const &

inlinenodiscard

Gets the error.

Returns

A const reference to the contained error

Exceptions

std::runtime_error

if the result contains a value

Definition at line 356 of file error_handling.h.

                                                   {
        if (has_value_) {
            throw std::runtime_error("Cannot get error from successful result");
        }
        return error_;
    }

References kcenon::thread::result< T >::error_, and kcenon::thread::result< T >::has_value_.

has_value()

template<typename T >

bool kcenon::thread::result< T >::has_value ( ) const

inlinenodiscardnoexcept

Checks if the result contains a value.

Returns

true if the result contains a value, false if it contains an error

Examples

mpmc_queue_sample.cpp.

Definition at line 281 of file error_handling.h.

                                                  {
        return has_value_;
    }

References kcenon::thread::result< T >::has_value_.

Referenced by basic_spsc_example(), kcenon::thread::aging_typed_job_queue_t< job_type >::dequeue(), kcenon::thread::aging_typed_job_queue_t< job_type >::dequeue(), mpmc_example(), performance_example(), and kcenon::thread::numa_work_stealer::steal_for().

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is_error()

template<typename T >

bool kcenon::thread::result< T >::is_error ( ) const

inlinenodiscardnoexcept

Checks if the result contains an error.

Returns

true if the result contains an error, false if it contains a value

Note

Added for API compatibility with common::Result

Definition at line 299 of file error_handling.h.

                                                 {
        return !has_value_;
    }

References kcenon::thread::result< T >::has_value_.

is_ok()

template<typename T >

bool kcenon::thread::result< T >::is_ok ( ) const

inlinenodiscardnoexcept

Checks if the result is successful.

Returns

true if the result contains a value, false if it contains an error

Note

Added for API compatibility with common::Result

Examples

adaptive_queue_sample.cpp, mpmc_queue_sample.cpp, queue_factory_sample.cpp, and typed_job_queue_sample.cpp.

Definition at line 290 of file error_handling.h.

                                              {
        return has_value_;
    }

References kcenon::thread::result< T >::has_value_.

Referenced by adaptive_behavior_example(), kcenon::thread::backpressure_job_queue::apply_backpressure(), batch_operations_example(), kcenon::thread::adaptive_job_queue::dequeue(), kcenon::thread::aging_typed_job_queue_t< job_type >::dequeue(), different_policies_example(), kcenon::thread::protected_job::do_work(), kcenon::thread::adaptive_job_queue::enqueue(), kcenon::thread::backpressure_job_queue::enqueue_batch(), kcenon::thread::dag_scheduler::execute_job(), kcenon::thread::autoscaler::execute_scaling(), kcenon::thread::backpressure_job_queue::handle_adaptive_policy(), kcenon::thread::backpressure_job_queue::handle_block_policy(), kcenon::thread::backpressure_job_queue::handle_drop_oldest_policy(), mpmc_typed_queue_example(), kcenon::thread::dag_scheduler::on_job_failed(), optimal_selection(), performance_monitoring_example(), policy_comparison_example(), practical_use_cases(), kcenon::thread::dag_job::set_work_with_result(), kcenon::thread::adapters::thread_pool_executor_adapter::submit(), task_scheduling_example(), kcenon::thread::adaptive_job_queue::try_dequeue(), web_server_simulation(), and kcenon::thread::dag_job_builder::work_with_result().

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map()

template<typename T >

template<typename Fn >

auto kcenon::thread::result< T >::map ( Fn && fn ) const -> result<std::invoke_result_t<Fn, const T&>>

inlinenodiscard

Maps the result to another type using a function.

Parameters

fn	The function to apply to the value

Returns

A new result with the mapped value or the original error

Definition at line 431 of file error_handling.h.

                                                                                      {
        using ResultType = result<std::invoke_result_t<Fn, const T&>>;
        
        if (has_value_) {
            return ResultType(std::invoke(std::forward<Fn>(fn), value_));
        }
        return ResultType(error_);
    }

References kcenon::thread::result< T >::error_, kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

operator bool()

template<typename T >

kcenon::thread::result< T >::operator bool ( ) const

inlineexplicitnodiscardnoexcept

Checks if the result contains a value.

Returns

true if the result contains a value, false if it contains an error

Definition at line 273 of file error_handling.h.

                                                          {
        return has_value_;
    }

References kcenon::thread::result< T >::has_value_.

value() [1/3]

template<typename T >

T & kcenon::thread::result< T >::value ( ) &

inlinenodiscard

Gets the value.

Returns

A reference to the contained value

Exceptions

std::runtime_error

if the result contains an error

Examples

adaptive_queue_sample.cpp, mpmc_queue_sample.cpp, queue_factory_sample.cpp, and typed_job_queue_sample.cpp.

Definition at line 308 of file error_handling.h.

                               {
        if (!has_value_) {
            throw std::runtime_error("Cannot access value of an error result");
        }
        return value_;
    }

References kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

Referenced by adaptive_behavior_example(), basic_spsc_example(), kcenon::thread::aging_typed_job_queue_t< job_type >::dequeue(), kcenon::thread::aging_typed_job_queue_t< job_type >::dequeue(), different_policies_example(), kcenon::thread::adaptive_job_queue::migrate_to_mode(), mpmc_example(), optimal_selection(), performance_monitoring_example(), policy_comparison_example(), practical_use_cases(), kcenon::thread::result_to_pair(), kcenon::thread::dag_job::set_work_with_result(), kcenon::thread::numa_work_stealer::steal_for(), task_scheduling_example(), kcenon::thread::aging_typed_job_queue_t< job_type >::try_dequeue_from_priority(), web_server_simulation(), and kcenon::thread::dag_job_builder::work_with_result().

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value() [2/3]

template<typename T >

T && kcenon::thread::result< T >::value ( ) &&

inlinenodiscard

Gets the value.

Returns

An rvalue reference to the contained value

Exceptions

std::runtime_error

if the result contains an error

Definition at line 332 of file error_handling.h.

                                 {
        if (!has_value_) {
            throw std::runtime_error("Cannot access value of an error result");
        }
        return std::move(value_);
    }

References kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

value() [3/3]

template<typename T >

const T & kcenon::thread::result< T >::value ( ) const &

inlinenodiscard

Gets the value.

Returns

A const reference to the contained value

Exceptions

std::runtime_error

if the result contains an error

Definition at line 320 of file error_handling.h.

                                           {
        if (!has_value_) {
            throw std::runtime_error("Cannot access value of an error result");
        }
        return value_;
    }

References kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

value_or() [1/2]

template<typename T >

template<typename U >

T kcenon::thread::result< T >::value_or ( U && default_value ) &&

inlinenodiscard

Gets the value or a default.

Parameters

default_value

The value to return if the result contains an error

Returns

The contained value or the default

Definition at line 394 of file error_handling.h.

                                                   {
        if (has_value_) {
            return std::move(value_);
        }
        return static_cast<T>(std::forward<U>(default_value));
    }

References kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

value_or() [2/2]

template<typename T >

template<typename U >

T kcenon::thread::result< T >::value_or ( U && default_value ) const &

inlinenodiscard

Gets the value or a default.

Parameters

default_value

The value to return if the result contains an error

Returns

The contained value or the default

Definition at line 381 of file error_handling.h.

                                                        {
        if (has_value_) {
            return value_;
        }
        return static_cast<T>(std::forward<U>(default_value));
    }

References kcenon::thread::result< T >::has_value_, and kcenon::thread::result< T >::value_.

value_or_throw() [1/2]

template<typename T >

T kcenon::thread::result< T >::value_or_throw ( ) &&

inlinenodiscard

Gets the value or throws an exception.

Returns

The contained value

Exceptions

std::runtime_error

with the error message if the result contains an error

Definition at line 418 of file error_handling.h.

                                        {
        if (has_value_) {
            return std::move(value_);
        }
        throw std::runtime_error(error_.to_string());
    }

References kcenon::thread::result< T >::error_, kcenon::thread::result< T >::has_value_, kcenon::thread::error::to_string(), and kcenon::thread::result< T >::value_.

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value_or_throw() [2/2]

template<typename T >

T kcenon::thread::result< T >::value_or_throw ( ) const &

inlinenodiscard

Gets the value or throws an exception.

Returns

The contained value

Exceptions

std::runtime_error

with the error message if the result contains an error

Definition at line 406 of file error_handling.h.

                                             {
        if (has_value_) {
            return value_;
        }
        throw std::runtime_error(error_.to_string());
    }

References kcenon::thread::result< T >::error_, kcenon::thread::result< T >::has_value_, kcenon::thread::error::to_string(), and kcenon::thread::result< T >::value_.

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Member Data Documentation

error_

template<typename T >

error kcenon::thread::result< T >::error_ {error_code::success, ""}

private

Definition at line 459 of file error_handling.h.

{error_code::success, ""};

Referenced by kcenon::thread::result< T >::and_then(), kcenon::thread::result< void >::and_then(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< void >::get_error(), kcenon::thread::result< void >::get_error(), kcenon::thread::result< void >::get_error(), kcenon::thread::result< T >::map(), kcenon::thread::result< void >::map(), kcenon::thread::result< T >::value_or_throw(), kcenon::thread::result< T >::value_or_throw(), and kcenon::thread::result< void >::value_or_throw().

has_value_

template<typename T >

bool kcenon::thread::result< T >::has_value_ = false

private

Definition at line 457 of file error_handling.h.

Referenced by kcenon::thread::result< T >::and_then(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< T >::get_error(), kcenon::thread::result< T >::has_value(), kcenon::thread::result< T >::is_error(), kcenon::thread::result< T >::is_ok(), kcenon::thread::result< T >::map(), kcenon::thread::result< T >::operator bool(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value_or(), kcenon::thread::result< T >::value_or(), kcenon::thread::result< T >::value_or_throw(), and kcenon::thread::result< T >::value_or_throw().

value_

template<typename T >

T kcenon::thread::result< T >::value_ {}

private

Definition at line 458 of file error_handling.h.

{};

Referenced by kcenon::thread::result< T >::and_then(), kcenon::thread::result< T >::map(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value(), kcenon::thread::result< T >::value_or(), kcenon::thread::result< T >::value_or(), kcenon::thread::result< T >::value_or_throw(), and kcenon::thread::result< T >::value_or_throw().

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The documentation for this class was generated from the following file:

• core/sync/include/error_handling.h