ValueContainer.h

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#pragma once

#include <OnixS/CME/iLink3/ABI.h>
#include <OnixS/CME/iLink3/messaging/Memory.h>

#include <new>

ONIXS_ILINK3_MESSAGING_TAGBASED_NAMESPACE_BEGIN

/// Container for a value.
ONIXS_ILINK3_LTWT_CLASS
ValueContainer
{
    enum
    {
        /// Capacity of the storage.
        ///
        /// The storage must be spacious enough
        /// to store all integer types, string refs,
        /// time-related typed and the Decimal.
        Capacity = 16
    };

    Byte bytes_[Capacity];

    /// This method is used to make g++ happy with the
    /// concept of storing a value in an array.
    void* place() ONIXS_ILINK3_NOTHROW
    {
        return static_cast<void*>(bytes_);
    }

    /// This method is used to make g++ happy with the
    /// concept of storing a value in an array.
    const void* place() const ONIXS_ILINK3_NOTHROW
    {
        return static_cast<const void*>(bytes_);
    }

public:
    /// Initializes the container.
    ValueContainer() ONIXS_ILINK3_DEFAULT;

    /// \return the stored value.
    template <typename Value>
    ONIXS_ILINK3_NODISCARD Value& get() ONIXS_ILINK3_NOTHROW
    {
        ONIXS_ILINK3_STATIC_ASSERT_MSG
        (
            (sizeof(Value) <= static_cast<size_t>(Capacity)), "Capacity is not sufficient for storing values of the given type."
        );

        return * static_cast<Value*> (place());
    }

    /// \return the stored value.
    template <typename Value>
    ONIXS_ILINK3_NODISCARD const Value& get() const ONIXS_ILINK3_NOTHROW
    {
        ONIXS_ILINK3_STATIC_ASSERT_MSG
        (
            (sizeof(Value) <= static_cast<size_t>(Capacity)), "Capacity of the storage is not sufficient to store values of the specified type."
        );

        return * static_cast<const Value*>(place());
    }

    /// Stores the given value.
    template<class Value>
    ValueContainer& assign(const Value& value) ONIXS_ILINK3_NOTHROW
    {
        ONIXS_ILINK3_STATIC_ASSERT_MSG
        (
            (sizeof(Value) <= static_cast<size_t>(Capacity)), "Capacity of the storage is not sufficient to store values of the specified type."
        );

#if defined (ONIXS_ILINK3_CXX11)
        static_assert(
            std::is_nothrow_copy_constructible<Value>::value,
            "must be noexcept");
#endif

        new (place()) Value(value);

        return *this;
    }
};

ONIXS_ILINK3_MESSAGING_TAGBASED_NAMESPACE_END