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