ValueContainer.h

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// Copyright Onix Solutions Limited [OnixS]. All rights reserved.
//
// This software owned by Onix Solutions Limited [OnixS] and is
// protected by copyright law and international copyright treaties.
//
// Access to and use of the software is governed by the terms of the applicable
// OnixS Software Services Agreement (the Agreement) and Customer end user license
// agreements granting a non-assignable, non-transferable and non-exclusive license
// to use the software for it's own data processing purposes under the terms defined
// in the Agreement.
//
// Except as otherwise granted within the terms of the Agreement, copying or
// reproduction of any part of this source code or associated reference material
// to any other location for further reproduction or redistribution, and any
// amendments to this copyright notice, are expressly prohibited.
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//
 
#pragma once
 
#include <new>
 
#include <OnixS/CME/MDH/Memory.h>
#include <OnixS/CME/MDH/Assertion.h>
 
ONIXS_CMEMDHFIX_NAMESPACE_BEGIN

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:
    ValueContainer() {}

    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());
    }

    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());
    }

    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