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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CRDTP_MAYBE_H_
#define CRDTP_MAYBE_H_
#include <cassert>
#include <memory>
namespace crdtp {
// =============================================================================
// detail::PtrMaybe, detail::ValueMaybe, templates for optional
// pointers / values which are used in ../lib/Forward_h.template.
// =============================================================================
namespace detail {
template <typename T>
class PtrMaybe {
public:
PtrMaybe() = default;
PtrMaybe(std::unique_ptr<T> value) : value_(std::move(value)) {}
PtrMaybe(PtrMaybe&& other) noexcept : value_(std::move(other.value_)) {}
void operator=(std::unique_ptr<T> value) { value_ = std::move(value); }
// std::optional<>-compatible accessors (preferred).
bool has_value() const { return !!value_; }
operator bool() const { return has_value(); }
const T& value() const& {
assert(has_value());
return *value_;
}
T& value() & {
assert(has_value());
return *value_;
}
T&& value() && {
assert(has_value());
return std::move(*value_);
}
const T& value_or(const T& default_value) const {
return has_value() ? *value_ : default_value;
}
T* operator->() { return &value(); }
const T* operator->() const { return &value(); }
T& operator*() & { return value(); }
const T& operator*() const& { return value(); }
T&& operator*() && { return std::move(value()); }
// Legacy Maybe<> accessors (deprecated).
T* fromJust() const {
assert(value_);
return value_.get();
}
T* fromMaybe(T* default_value) const {
return value_ ? value_.get() : default_value;
}
bool isJust() const { return value_ != nullptr; }
private:
std::unique_ptr<T> value_;
};
template <typename T>
class ValueMaybe {
public:
ValueMaybe() : is_just_(false), value_() {}
ValueMaybe(T value) : is_just_(true), value_(std::move(value)) {}
ValueMaybe(ValueMaybe&& other) noexcept
: is_just_(other.is_just_), value_(std::move(other.value_)) {}
void operator=(T value) {
value_ = std::move(value);
is_just_ = true;
}
// std::optional<>-compatible accessors (preferred).
bool has_value() const { return is_just_; }
operator bool() const { return has_value(); }
const T& value() const& {
assert(is_just_);
return value_;
}
T& value() & {
assert(is_just_);
return value_;
}
T&& value() && {
assert(is_just_);
return *std::move(value_);
}
template <typename U>
T value_or(U&& default_value) const& {
return is_just_ ? value_ : std::forward<U>(default_value);
}
template <typename U>
T value_or(U&& default_value) && {
return is_just_ ? std::move(value_) : std::forward<U>(default_value);
}
T* operator->() { return &value(); }
const T* operator->() const { return &value(); }
T& operator*() & { return value(); }
const T& operator*() const& { return value(); }
T&& operator*() && { return std::move(value()); }
// Legacy Maybe<> accessors (deprecated).
const T& fromJust() const {
assert(is_just_);
return value_;
}
const T& fromMaybe(const T& default_value) const {
return is_just_ ? value_ : default_value;
}
bool isJust() const { return is_just_; }
private:
bool is_just_;
T value_;
};
template <typename T>
struct MaybeTypedef {
typedef PtrMaybe<T> type;
};
template <>
struct MaybeTypedef<bool> {
typedef ValueMaybe<bool> type;
};
template <>
struct MaybeTypedef<int> {
typedef ValueMaybe<int> type;
};
template <>
struct MaybeTypedef<double> {
typedef ValueMaybe<double> type;
};
template <>
struct MaybeTypedef<std::string> {
typedef ValueMaybe<std::string> type;
};
} // namespace detail
template <typename T>
using Maybe = typename detail::MaybeTypedef<T>::type;
} // namespace crdtp
#endif // CRDTP_MAYBE_H_
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