optional.h

Go to the documentation of this file.

 //-----------------------------------------------------------------------------
// Project     : VST SDK
//
// Category    : Helpers
// Filename    : public.sdk/source/vst/utility/optional.h
// Created by  : Steinberg, 08/2016
// Description : optional helper
//
//-----------------------------------------------------------------------------
// LICENSE
// (c) 2023, Steinberg Media Technologies GmbH, All Rights Reserved
//-----------------------------------------------------------------------------
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
// 
//   * Redistributions of source code must retain the above copyright notice, 
//     this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation 
//     and/or other materials provided with the distribution.
//   * Neither the name of the Steinberg Media Technologies nor the names of its
//     contributors may be used to endorse or promote products derived from this 
//     software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
// IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE  OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.
//-----------------------------------------------------------------------------
 
#pragma once
 
#include <cassert>
#include <memory>
#include <utility>
 
//------------------------------------------------------------------------
namespace VST3 {
 
//------------------------------------------------------------------------
template <typename T>
struct Optional
{
    Optional () noexcept : valid (false) {}
    explicit Optional (const T& v) noexcept : _value (v), valid (true) {}
    Optional (T&& v) noexcept : _value (std::move (v)), valid (true) {}
 
    Optional (Optional&& other) noexcept { *this = std::move (other); }
    Optional& operator= (Optional&& other) noexcept
    {
        valid = other.valid;
        _value = std::move (other._value);
        return *this;
    }
 
    explicit operator bool () const noexcept
    {
        setValidationChecked ();
        return valid;
    }
 
    const T& operator* () const noexcept
    {
        checkValid ();
        return _value;
    }
 
    const T* operator-> () const noexcept
    {
        checkValid ();
        return &_value;
    }
 
    T& operator* () noexcept
    {
        checkValid ();
        return _value;
    }
 
    T* operator-> () noexcept
    {
        checkValid ();
        return &_value;
    }
 
    T&& value () noexcept
    {
        checkValid ();
        return move (_value);
    }
 
    const T& value () const noexcept
    {
        checkValid ();
        return _value;
    }
 
    void swap (T& other) noexcept
    {
        checkValid ();
        auto tmp = std::move (other);
        other = std::move (_value);
        _value = std::move (tmp);
    }
 
private:
    T _value {};
    bool valid;
 
#if !defined(NDEBUG)
    mutable bool validationChecked {false};
#endif
 
    void setValidationChecked () const
    {
#if !defined(NDEBUG)
        validationChecked = true;
#endif
    }
    void checkValid () const
    {
#if !defined(NDEBUG)
        assert (validationChecked);
#endif
    }
};
 
//------------------------------------------------------------------------
}