ValueContainer.h

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// Copyright Onix Solutions Limited [OnixS]. All rights reserved.
//
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#pragma once

#include <new>

#include <OnixS/CME/MDH/Memory.h>
#include <OnixS/CME/MDH/Assertion.h>

ONIXS_CMEMDHFIX_NAMESPACE_BEGIN

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

    Byte bytes_[Capacity];

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

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

public:
    /// Initializes the container.
    ValueContainer() {}

    /// Provides access to the value stored
    /// in the container assuming the value
    /// is of the specified type.
    template <typename Value>
    Value& get()
    {
        ONIXS_SASSERT_MSG(
            sizeof(Value) <= Capacity,
            "Capacity isn't sufficient for "
            "storing values of the given type. "
        );

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

    /// Provides access to the value stored
    /// in the container assuming the value
    /// is of the specified type.
    template <typename Value>
    const Value& get() const
    {
        ONIXS_SASSERT_MSG(
            sizeof(Value) <= Capacity,
            "Capacity of the storage isn't "
            "sufficient to store values "
            "of the specified type. "
        );

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

    /// Stores the given value in the container.
    template <class Value>
    ValueContainer& assign(const Value& value)
    {
        ONIXS_SASSERT_MSG(
            sizeof(Value) <= Capacity,
            "Capacity of the storage isn't "
            "sufficient to store values "
            "of the specified type. "
        );

        new (place()) Value(value);

        return *this;
    }
};

ONIXS_CMEMDHFIX_NAMESPACE_END