379 lines
8.3 KiB
C++
379 lines
8.3 KiB
C++
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/*
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* Result.hpp
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*
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* Created on: 11 May 2023
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* Author: malyarenko
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*/
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/*
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* <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <EFBFBD><EFBFBD><EFBFBD> C++ <EFBFBD> <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> header-only <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> Result
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* https://github.com/oktal/result
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*/
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#ifndef UMLIBRARY_COMMON_RESULT_HH_
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#define UMLIBRARY_COMMON_RESULT_HH_
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#include <cstddef>
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#include <cstdlib>
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#include <utility>
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#include <new>
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#include <type_traits>
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#include "Error.hh"
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namespace result {
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namespace types {
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template< typename T >
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struct Ok {
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#if __cplusplus >= 201103L
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Ok(T&& value)
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: value(std::move(value)) { }
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#else
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Ok(T& value)
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: value(value) { }
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#endif
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T value;
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};
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template<>
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struct Ok<void> { };
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template< typename E >
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struct Err {
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#if __cplusplus >= 201103L
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Err(E&& value)
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: value(std::move(value)) { }
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#else
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Err(E& value)
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: value(value) { }
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#endif
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Err(const E& value)
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: value(value) { }
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E value;
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};
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} /* namespace types */
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} /* namespace result */
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inline result::types::Ok<void> Ok() {
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return result::types::Ok<void>();
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}
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#if __cplusplus >= 201103L
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template<typename T, typename CleanT = typename std::decay<T>::type>
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result::types::Ok<CleanT> Ok(T&& value) {
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return result::types::Ok<CleanT>(std::forward<CleanT>(value));
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}
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template<typename E, typename CleanE = typename std::decay<E>::type>
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result::types::Err<CleanE> Err(E&& value) {
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return result::types::Err<CleanE>(std::forward<CleanE>(value));
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}
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#else
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template<typename T, typename CleanT = typename std::tr1::decay<T>::type>
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result::types::Ok<CleanT> Ok(T& value) {
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return result::types::Ok<CleanT>(value);
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}
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template<typename E, typename CleanE = typename std::tr1::decay<E>::type>
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result::types::Err<CleanE> Err(E& value) {
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return result::types::Err<CleanE>(value);
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}
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#endif
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namespace result {
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namespace storage {
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struct OkTag { };
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struct ErrTag { };
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template< typename T, typename E >
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class Storage {
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public:
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Storage()
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: initialized(false) { }
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void construct(result::types::Ok<T> ok) {
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new (&storage) T(ok.value);
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initialized = true;
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}
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void construct(result::types::Err<E> err) {
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new (&storage) E(err.value);
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initialized = true;
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}
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#if __cplusplus >= 201103L
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template< typename U >
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void constructRaw(U&& value) {
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typedef typename std::decay<U>::type CleanU;
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new (&storage) CleanU(std::forward<U>(value));
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initialized = true;
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}
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#else
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template< typename U >
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void constructRaw(U& value) {
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typedef typename std::tr1::decay<U>::type CleanU;
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new (&storage) CleanU(value);
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initialized = true;
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}
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#endif
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template< typename U >
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const U& get() const {
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return *reinterpret_cast< const U * >(&storage);
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}
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template< typename U >
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U& get() {
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return *reinterpret_cast< U * >(&storage);
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}
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void destroy(OkTag) {
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if (initialized) {
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get<T>().~T();
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initialized = false;
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}
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}
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void destroy(ErrTag) {
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if (initialized) {
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get<E>().~E();
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initialized = false;
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}
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}
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private:
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static constexpr std::size_t Size = sizeof(T) > sizeof(E) ? sizeof(T) : sizeof(E);
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static constexpr std::size_t Align = alignof(T) > alignof(E) ? alignof(T) : alignof(E);
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#if __cplusplus >= 201103L
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typedef typename std::aligned_storage<Size, Align>::type type;
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type storage;
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#else
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unsigned long storage[1+Size/2];
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#endif
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bool initialized;
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};
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template< typename E >
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struct Storage< void, E > {
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#if __cplusplus >= 201103L
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typedef typename std::aligned_storage<sizeof(E), alignof(E)>::type type;
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type storage;
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#else
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unsigned long storage[1+sizeof(E)/2];
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#endif
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void construct(result::types::Ok<void>) {
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initialized = true;
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}
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void construct(result::types::Err<E> err) {
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new (&storage) E(err.value);
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initialized = true;
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}
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#if __cplusplus >= 201103L
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template< typename U >
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void constructRaw(U&& value) {
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typedef typename std::decay<U>::type CleanU;
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new (&storage) CleanU(std::forward<U>(value));
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initialized = true;
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}
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#else
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template< typename U >
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void constructRaw(U& value) {
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typedef typename std::tr1::decay<U>::type CleanU;
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new (&storage) CleanU(value);
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initialized = true;
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}
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#endif
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void destroy(OkTag) {
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initialized = false;
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}
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void destroy(ErrTag) {
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if (initialized) {
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get<E>().~E();
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initialized = false;
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}
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}
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template<typename U>
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const U& get() const {
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return *reinterpret_cast< const U * >(&storage);
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}
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template<typename U>
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U& get() {
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return *reinterpret_cast< U * >(&storage);
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}
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bool initialized;
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};
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template< typename T, typename E >
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struct Constructor {
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static void copy(const Storage<T, E>& src, Storage<T, E>& dst, OkTag) {
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dst.constructRaw(src.template get<T>());
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}
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static void copy(const Storage<T, E>& src, Storage<T, E>& dst, ErrTag) {
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dst.constructRaw(src.template get<E>());
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}
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#if __cplusplus >= 201103L
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static void move(Storage<T, E>&& src, Storage<T, E>& dst, OkTag) {
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dst.constructRaw(std::move(src.template get<T>()));
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src.destroy(OkTag());
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}
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static void move(Storage<T, E>&& src, Storage<T, E>& dst, ErrTag) {
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dst.constructRaw(std::move(src.template get<E>()));
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src.destroy(ErrTag());
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}
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#endif
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};
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template<typename E>
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struct Constructor<void, E> {
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static void copy(const Storage<void, E>& src, Storage<void, E>& dst, OkTag) { }
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static void copy(const Storage<void, E>& src, Storage<void, E>& dst, ErrTag) {
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dst.constructRaw(src.template get<E>());
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}
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#if __cplusplus >= 201103L
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static void move(Storage<void, E>&& src, Storage<void, E>& dst, OkTag) { }
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static void move(Storage<void, E>&& src, Storage<void, E>& dst, ErrTag) {
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dst.constructRaw(std::move(src.template get<E>()));
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src.destroy(ErrTag());
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}
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#endif
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};
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} /* namespace storage */
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} /* namespace result */
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template< typename T, typename E >
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class Result {
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public:
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#if __cplusplus >= 201103L
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static_assert(!std::is_same<E, void>::value, "void error type is not allowed");
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#endif
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typedef result::storage::Storage<T, E> storage_type;
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#if __cplusplus >= 201103L
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Result(result::types::Ok<T> ok)
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: ok(true)
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{
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storage.construct(std::move(ok));
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}
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Result(result::types::Err<E> err)
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: ok(false)
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{
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storage.construct(std::move(err));
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}
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Result(Result&& other) {
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if (other.isOk()) {
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result::storage::Constructor<T, E>::move(std::move(other.storage), storage, result::storage::OkTag());
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ok = true;
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} else {
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result::storage::Constructor<T, E>::move(std::move(other.storage), storage, result::storage::ErrTag());
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ok = false;
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}
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}
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#else
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Result(result::types::Ok<T> ok)
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: ok(true)
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{
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storage.construct(ok);
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}
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Result(result::types::Err<E> err)
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: ok(false)
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{
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storage.construct(err);
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}
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#endif
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Result(const Result& other) {
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if (other.isOk()) {
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result::storage::Constructor<T, E>::copy(other.storage, storage, result::storage::OkTag());
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ok = true;
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} else {
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result::storage::Constructor<T, E>::copy(other.storage, storage, result::storage::ErrTag());
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ok = false;
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}
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}
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~Result() {
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if (ok) {
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storage.destroy(result::storage::OkTag());
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} else {
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storage.destroy(result::storage::ErrTag());
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}
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}
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bool isOk() const {
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return ok;
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}
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bool isErr() const {
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return !ok;
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}
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#if __cplusplus >= 201103L
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template< typename U = T >
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typename std::enable_if<!std::is_same<U, void>::value, U >::type
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unwrap() const {
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if (isOk()) {
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return storage.template get<U>();
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}
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std::abort();
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}
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#else
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template< typename U = T >
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typename std::tr1::enable_if<!std::tr1::is_same<U, void>::value, U >::type
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unwrap() const {
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if (isOk()) {
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return storage.template get<U>();
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}
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std::abort();
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}
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#endif
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E unwrapErr() const {
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if (isErr()) {
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return storage.template get<E>();
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}
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std::abort();
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}
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private:
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bool ok;
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storage_type storage;
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};
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#endif /* UMLIBRARY_COMMON_RESULT_HH_ */
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