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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229335 91177308-0d34-0410-b5e6-96231b3b80d8
210 lines
6.4 KiB
C++
210 lines
6.4 KiB
C++
//===-- Optional.h - Simple variant for passing optional values ---*- C++ -*-=//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file provides Optional, a template class modeled in the spirit of
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// OCaml's 'opt' variant. The idea is to strongly type whether or not
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// a value can be optional.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_OPTIONAL_H
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#define LLVM_ADT_OPTIONAL_H
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#include "llvm/ADT/None.h"
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#include "llvm/Support/AlignOf.h"
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#include "llvm/Support/Compiler.h"
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#include <cassert>
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#include <new>
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#include <utility>
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namespace llvm {
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template<typename T>
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class Optional {
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AlignedCharArrayUnion<T> storage;
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bool hasVal;
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public:
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typedef T value_type;
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Optional(NoneType) : hasVal(false) {}
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explicit Optional() : hasVal(false) {}
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Optional(const T &y) : hasVal(true) {
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new (storage.buffer) T(y);
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}
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Optional(const Optional &O) : hasVal(O.hasVal) {
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if (hasVal)
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new (storage.buffer) T(*O);
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}
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Optional(T &&y) : hasVal(true) {
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new (storage.buffer) T(std::forward<T>(y));
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}
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Optional(Optional<T> &&O) : hasVal(O) {
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if (O) {
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new (storage.buffer) T(std::move(*O));
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O.reset();
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}
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}
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Optional &operator=(T &&y) {
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if (hasVal)
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**this = std::move(y);
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else {
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new (storage.buffer) T(std::move(y));
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hasVal = true;
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}
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return *this;
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}
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Optional &operator=(Optional &&O) {
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if (!O)
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reset();
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else {
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*this = std::move(*O);
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O.reset();
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}
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return *this;
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}
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/// Create a new object by constructing it in place with the given arguments.
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template<typename ...ArgTypes>
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void emplace(ArgTypes &&...Args) {
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reset();
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hasVal = true;
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new (storage.buffer) T(std::forward<ArgTypes>(Args)...);
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}
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static inline Optional create(const T* y) {
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return y ? Optional(*y) : Optional();
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}
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// FIXME: these assignments (& the equivalent const T&/const Optional& ctors)
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// could be made more efficient by passing by value, possibly unifying them
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// with the rvalue versions above - but this could place a different set of
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// requirements (notably: the existence of a default ctor) when implemented
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// in that way. Careful SFINAE to avoid such pitfalls would be required.
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Optional &operator=(const T &y) {
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if (hasVal)
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**this = y;
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else {
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new (storage.buffer) T(y);
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hasVal = true;
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}
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return *this;
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}
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Optional &operator=(const Optional &O) {
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if (!O)
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reset();
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else
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*this = *O;
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return *this;
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}
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void reset() {
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if (hasVal) {
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(**this).~T();
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hasVal = false;
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}
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}
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~Optional() {
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reset();
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}
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const T* getPointer() const { assert(hasVal); return reinterpret_cast<const T*>(storage.buffer); }
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T* getPointer() { assert(hasVal); return reinterpret_cast<T*>(storage.buffer); }
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const T& getValue() const LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
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T& getValue() LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
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explicit operator bool() const { return hasVal; }
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bool hasValue() const { return hasVal; }
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const T* operator->() const { return getPointer(); }
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T* operator->() { return getPointer(); }
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const T& operator*() const LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
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T& operator*() LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
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template <typename U>
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LLVM_CONSTEXPR T getValueOr(U &&value) const LLVM_LVALUE_FUNCTION {
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return hasValue() ? getValue() : std::forward<U>(value);
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}
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#if LLVM_HAS_RVALUE_REFERENCE_THIS
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T&& getValue() && { assert(hasVal); return std::move(*getPointer()); }
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T&& operator*() && { assert(hasVal); return std::move(*getPointer()); }
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template <typename U>
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T getValueOr(U &&value) && {
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return hasValue() ? std::move(getValue()) : std::forward<U>(value);
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}
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#endif
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};
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template <typename T> struct isPodLike;
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template <typename T> struct isPodLike<Optional<T> > {
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// An Optional<T> is pod-like if T is.
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static const bool value = isPodLike<T>::value;
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};
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator==(const Optional<T> &X, const Optional<U> &Y);
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator!=(const Optional<T> &X, const Optional<U> &Y);
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator<(const Optional<T> &X, const Optional<U> &Y);
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator<=(const Optional<T> &X, const Optional<U> &Y);
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator>=(const Optional<T> &X, const Optional<U> &Y);
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/// \brief Poison comparison between two \c Optional objects. Clients needs to
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/// explicitly compare the underlying values and account for empty \c Optional
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/// objects.
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///
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/// This routine will never be defined. It returns \c void to help diagnose
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/// errors at compile time.
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template<typename T, typename U>
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void operator>(const Optional<T> &X, const Optional<U> &Y);
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} // end llvm namespace
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#endif
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