ClickHouse/base/poco/Foundation/include/Poco/Any.h

//
// Any.h
//
// Library: Foundation
// Package: Core
// Module:	Any
//
// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
// Extracted from Boost 1.33.1 lib and adapted for poco: Peter Schojer/AppliedInformatics 2006-02-02
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_Any_INCLUDED
#define Foundation_Any_INCLUDED


#include <algorithm>
#include <cstring>
#include <typeinfo>
#include "Poco/Exception.h"
#include "Poco/MetaProgramming.h"


namespace Poco
{


class Any;


namespace Dynamic
{

    class Var;
    class VarHolder;
    template <class>
    class VarHolderImpl;

}

#ifndef POCO_NO_SOO

#    ifndef POCO_ENABLE_CPP11
// C++11 needed for std::aligned_storage
#        error "Any SOO can only be enabled with C++11 support"
#    endif

template <typename PlaceholderT, unsigned int SizeV = POCO_SMALL_OBJECT_SIZE>
union Placeholder
/// ValueHolder union (used by Poco::Any and Poco::Dynamic::Var for small
/// object optimization, when enabled).
///
/// If Holder<Type> fits into POCO_SMALL_OBJECT_SIZE bytes of storage,
/// it will be placement-new-allocated into the local buffer
/// (i.e. there will be no heap-allocation). The local buffer size is one byte
/// larger - [POCO_SMALL_OBJECT_SIZE + 1], additional byte value indicating
/// where the object was allocated (0 => heap, 1 => local).
{
public:
    struct Size
    {
        static const unsigned int value = SizeV;
    };

    Placeholder() { erase(); }

    void erase() { std::memset(holder, 0, sizeof(Placeholder)); }

    bool isLocal() const { return holder[SizeV] != 0; }

    void setLocal(bool local) const { holder[SizeV] = local ? 1 : 0; }

    PlaceholderT * content() const
    {
        if (isLocal())
            return reinterpret_cast<PlaceholderT *>(holder);
        else
            return pHolder;
    }

// MSVC71,80 won't extend friendship to nested class (Any::Holder)
#    if !defined(POCO_MSVC_VERSION) || (defined(POCO_MSVC_VERSION) && (POCO_MSVC_VERSION > 80))
private:
#    endif
    typedef typename std::aligned_storage<SizeV + 1>::type AlignerType;

    PlaceholderT * pHolder;
    mutable char holder[SizeV + 1];
    AlignerType aligner;

    friend class Any;
    friend class Dynamic::Var;
    friend class Dynamic::VarHolder;
    template <class>
    friend class Dynamic::VarHolderImpl;
};


#else // !POCO_NO_SOO


template <typename PlaceholderT>
union Placeholder
/// ValueHolder union (used by Poco::Any and Poco::Dynamic::Var for small
/// object optimization, when enabled).
///
/// If Holder<Type> fits into POCO_SMALL_OBJECT_SIZE bytes of storage,
/// it will be placement-new-allocated into the local buffer
/// (i.e. there will be no heap-allocation). The local buffer size is one byte
/// larger - [POCO_SMALL_OBJECT_SIZE + 1], additional byte value indicating
/// where the object was allocated (0 => heap, 1 => local).
{
public:
    Placeholder() { }

    PlaceholderT * content() const { return pHolder; }

// MSVC71,80 won't extend friendship to nested class (Any::Holder)
#    if !defined(POCO_MSVC_VERSION) || (defined(POCO_MSVC_VERSION) && (POCO_MSVC_VERSION > 80))
private:
#    endif

    PlaceholderT * pHolder;

    friend class Any;
    friend class Dynamic::Var;
    friend class Dynamic::VarHolder;
    template <class>
    friend class Dynamic::VarHolderImpl;
};


#endif // POCO_NO_SOO


class Any
/// An Any class represents a general type and is capable of storing any type, supporting type-safe extraction
/// of the internally stored data.
///
/// Code taken from the Boost 1.33.1 library. Original copyright by Kevlin Henney. Modified for Poco
/// by Applied Informatics.
///
/// Modified for small object optimization support (optionally supported through conditional compilation)
/// by Alex Fabijanic.
{
public:
#ifndef POCO_NO_SOO

    Any()
    /// Creates an empty any type.
    {
    }

    template <typename ValueType>
    Any(const ValueType & value)
    /// Creates an any which stores the init parameter inside.
    ///
    /// Example:
    ///   Any a(13);
    ///   Any a(string("12345"));
    {
        construct(value);
    }

    Any(const Any & other)
    /// Copy constructor, works with both empty and initialized Any values.
    {
        if ((this != &other) && !other.empty())
            construct(other);
    }

    ~Any()
    /// Destructor. If Any is locally held, calls ValueHolder destructor;
    /// otherwise, deletes the placeholder from the heap.
    {
        if (!empty())
        {
            if (_valueHolder.isLocal())
                destruct();
            else
                delete content();
        }
    }

    Any & swap(Any & other)
    /// Swaps the content of the two Anys.
    ///
    /// When small object optimization is enabled, swap only
    /// has no-throw guarantee when both (*this and other)
    /// objects are allocated on the heap.
    {
        if (this == &other)
            return *this;

        if (!_valueHolder.isLocal() && !other._valueHolder.isLocal())
        {
            std::swap(_valueHolder.pHolder, other._valueHolder.pHolder);
        }
        else
        {
            Any tmp(*this);
            try
            {
                if (_valueHolder.isLocal())
                    destruct();
                construct(other);
                other = tmp;
            }
            catch (...)
            {
                construct(tmp);
                throw;
            }
        }

        return *this;
    }

    template <typename ValueType>
    Any & operator=(const ValueType & rhs)
    /// Assignment operator for all types != Any.
    ///
    /// Example:
    ///   Any a = 13;
    ///   Any a = string("12345");
    {
        construct(rhs);
        return *this;
    }

    Any & operator=(const Any & rhs)
    /// Assignment operator for Any.
    {
        if ((this != &rhs) && !rhs.empty())
            construct(rhs);
        else if ((this != &rhs) && rhs.empty())
            _valueHolder.erase();

        return *this;
    }

    bool empty() const
    /// Returns true if the Any is empty.
    {
        char buf[POCO_SMALL_OBJECT_SIZE] = {0};
        return 0 == std::memcmp(_valueHolder.holder, buf, POCO_SMALL_OBJECT_SIZE);
    }

    const std::type_info & type() const
    /// Returns the type information of the stored content.
    /// If the Any is empty typeid(void) is returned.
    /// It is recommended to always query an Any for its type info before
    /// trying to extract data via an AnyCast/RefAnyCast.
    {
        return empty() ? typeid(void) : content()->type();
    }

private:
    class ValueHolder
    {
    public:
        virtual ~ValueHolder() { }

        virtual const std::type_info & type() const = 0;
        virtual void clone(Placeholder<ValueHolder> *) const = 0;
    };

    template <typename ValueType>
    class Holder : public ValueHolder
    {
    public:
        Holder(const ValueType & value) : _held(value) { }

        virtual const std::type_info & type() const { return typeid(ValueType); }

        virtual void clone(Placeholder<ValueHolder> * pPlaceholder) const
        {
            if ((sizeof(Holder<ValueType>) <= POCO_SMALL_OBJECT_SIZE))
            {
                new ((ValueHolder *)pPlaceholder->holder) Holder(_held);
                pPlaceholder->setLocal(true);
            }
            else
            {
                pPlaceholder->pHolder = new Holder(_held);
                pPlaceholder->setLocal(false);
            }
        }

        ValueType _held;

    private:
        Holder & operator=(const Holder &);
    };

    ValueHolder * content() const
    {
        return _valueHolder.content();
    }

    template <typename ValueType>
    void construct(const ValueType & value)
    {
        if (sizeof(Holder<ValueType>) <= Placeholder<ValueType>::Size::value)
        {
            new (reinterpret_cast<ValueHolder *>(_valueHolder.holder)) Holder<ValueType>(value);
            _valueHolder.setLocal(true);
        }
        else
        {
            _valueHolder.pHolder = new Holder<ValueType>(value);
            _valueHolder.setLocal(false);
        }
    }

    void construct(const Any & other)
    {
        if (!other.empty())
            other.content()->clone(&_valueHolder);
        else
            _valueHolder.erase();
    }

    void destruct()
    {
        content()->~ValueHolder();
    }

    Placeholder<ValueHolder> _valueHolder;


#else // if POCO_NO_SOO


    Any() : _pHolder(0)
    /// Creates an empty any type.
    {
    }

    template <typename ValueType>
    Any(const ValueType & value) : _pHolder(new Holder<ValueType>(value))
    /// Creates an any which stores the init parameter inside.
    ///
    /// Example:
    ///	 Any a(13);
    ///	 Any a(string("12345"));
    {
    }

    Any(const Any & other) : _pHolder(other._pHolder ? other._pHolder->clone() : 0)
    /// Copy constructor, works with both empty and initialized Any values.
    {
    }

    ~Any()
    {
        delete _pHolder;
    }

    Any & swap(Any & rhs)
    /// Swaps the content of the two Anys.
    {
        std::swap(_pHolder, rhs._pHolder);
        return *this;
    }

    template <typename ValueType>
    Any & operator=(const ValueType & rhs)
    /// Assignment operator for all types != Any.
    ///
    /// Example:
    ///   Any a = 13;
    ///   Any a = string("12345");
    {
        Any(rhs).swap(*this);
        return *this;
    }

    Any & operator=(const Any & rhs)
    /// Assignment operator for Any.
    {
        Any(rhs).swap(*this);
        return *this;
    }

    bool empty() const
    /// Returns true if the Any is empty.
    {
        return !_pHolder;
    }

    const std::type_info & type() const
    /// Returns the type information of the stored content.
    /// If the Any is empty typeid(void) is returned.
    /// It is recommended to always query an Any for its type info before
    /// trying to extract data via an AnyCast/RefAnyCast.
    {
        return _pHolder ? _pHolder->type() : typeid(void);
    }

private:
    class ValueHolder
    {
    public:
        virtual ~ValueHolder() { }

        virtual const std::type_info & type() const = 0;
        virtual ValueHolder * clone() const = 0;
    };

    template <typename ValueType>
    class Holder : public ValueHolder
    {
    public:
        Holder(const ValueType & value) : _held(value) { }

        virtual const std::type_info & type() const { return typeid(ValueType); }

        virtual ValueHolder * clone() const { return new Holder(_held); }

        ValueType _held;

    private:
        Holder & operator=(const Holder &);
    };

    ValueHolder * content() const
    {
        return _pHolder;
    }

private:
    ValueHolder * _pHolder;

#endif // POCO_NO_SOO

    template <typename ValueType>
    friend ValueType * AnyCast(Any *);

    template <typename ValueType>
    friend ValueType * UnsafeAnyCast(Any *);
};


template <typename ValueType>
ValueType * AnyCast(Any * operand)
/// AnyCast operator used to extract the ValueType from an Any*. Will return a pointer
/// to the stored value.
///
/// Example Usage:
///	 MyType* pTmp = AnyCast<MyType*>(pAny).
/// Will return NULL if the cast fails, i.e. types don't match.
{
    return operand && operand->type() == typeid(ValueType) ? &static_cast<Any::Holder<ValueType> *>(operand->content())->_held : 0;
}


template <typename ValueType>
const ValueType * AnyCast(const Any * operand)
/// AnyCast operator used to extract a const ValueType pointer from an const Any*. Will return a const pointer
/// to the stored value.
///
/// Example Usage:
///	 const MyType* pTmp = AnyCast<MyType*>(pAny).
/// Will return NULL if the cast fails, i.e. types don't match.
{
    return AnyCast<ValueType>(const_cast<Any *>(operand));
}


template <typename ValueType>
ValueType AnyCast(Any & operand)
/// AnyCast operator used to extract a copy of the ValueType from an Any&.
///
/// Example Usage:
///	 MyType tmp = AnyCast<MyType>(anAny).
/// Will throw a BadCastException if the cast fails.
/// Dont use an AnyCast in combination with references, i.e. MyType& tmp = ... or const MyType& tmp = ...
/// Some compilers will accept this code although a copy is returned. Use the RefAnyCast in
/// these cases.
{
    typedef typename TypeWrapper<ValueType>::TYPE NonRef;

    NonRef * result = AnyCast<NonRef>(&operand);
    if (!result)
        throw BadCastException("Failed to convert between Any types");
    return *result;
}


template <typename ValueType>
ValueType AnyCast(const Any & operand)
/// AnyCast operator used to extract a copy of the ValueType from an const Any&.
///
/// Example Usage:
///	 MyType tmp = AnyCast<MyType>(anAny).
/// Will throw a BadCastException if the cast fails.
/// Dont use an AnyCast in combination with references, i.e. MyType& tmp = ... or const MyType& = ...
/// Some compilers will accept this code although a copy is returned. Use the RefAnyCast in
/// these cases.
{
    typedef typename TypeWrapper<ValueType>::TYPE NonRef;

    return AnyCast<NonRef &>(const_cast<Any &>(operand));
}


template <typename ValueType>
const ValueType & RefAnyCast(const Any & operand)
/// AnyCast operator used to return a const reference to the internal data.
///
/// Example Usage:
///	 const MyType& tmp = RefAnyCast<MyType>(anAny);
{
    ValueType * result = AnyCast<ValueType>(const_cast<Any *>(&operand));
    if (!result)
        throw BadCastException("RefAnyCast: Failed to convert between const Any types");
    return *result;
}


template <typename ValueType>
ValueType & RefAnyCast(Any & operand)
/// AnyCast operator used to return a reference to the internal data.
///
/// Example Usage:
///	 MyType& tmp = RefAnyCast<MyType>(anAny);
{
    ValueType * result = AnyCast<ValueType>(&operand);
    if (!result)
        throw BadCastException("RefAnyCast: Failed to convert between Any types");
    return *result;
}


template <typename ValueType>
ValueType * UnsafeAnyCast(Any * operand)
/// The "unsafe" versions of AnyCast are not part of the
/// public interface and may be removed at any time. They are
/// required where we know what type is stored in the any and can't
/// use typeid() comparison, e.g., when our types may travel across
/// different shared libraries.
{
    return &static_cast<Any::Holder<ValueType> *>(operand->content())->_held;
}


template <typename ValueType>
const ValueType * UnsafeAnyCast(const Any * operand)
/// The "unsafe" versions of AnyCast are not part of the
/// public interface and may be removed at any time. They are
/// required where we know what type is stored in the any and can't
/// use typeid() comparison, e.g., when our types may travel across
/// different shared libraries.
{
    return AnyCast<ValueType>(const_cast<Any *>(operand));
}


} // namespace Poco


#endif