ImfAttribute.h

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//
// SPDX-License-Identifier: BSD-3-Clause
// Copyright (c) Contributors to the OpenEXR Project.
//

#ifndef INCLUDED_IMF_ATTRIBUTE_H
#define INCLUDED_IMF_ATTRIBUTE_H

//-----------------------------------------------------------------------------
//
//      class Attribute
//
//-----------------------------------------------------------------------------

#include "ImfForward.h"

#include "ImfIO.h"
#include "ImfXdr.h"

#include "IexBaseExc.h"

#include <cstring>
#include <typeinfo>

#if defined(_MSC_VER)
// suppress warning about non-exported base classes
#    pragma warning(push)
#    pragma warning(disable : 4251)
#    pragma warning(disable : 4275)
#endif

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER

class IMF_EXPORT_TYPE Attribute
{
public:
    //---------------------------
    // Constructor and destructor
    //---------------------------

    IMF_EXPORT Attribute ();
    IMF_EXPORT virtual ~Attribute ();

    //-------------------------------
    // Get this attribute's type name
    //-------------------------------

    virtual const char* typeName () const = 0;

    //------------------------------
    // Make a copy of this attribute
    //------------------------------

    virtual Attribute* copy () const = 0;

    //----------------------------------------
    // Type-specific attribute I/O and copying
    //----------------------------------------

    virtual void writeValueTo (
        OPENEXR_IMF_INTERNAL_NAMESPACE::OStream& os, int version) const = 0;

    virtual void readValueFrom (
        OPENEXR_IMF_INTERNAL_NAMESPACE::IStream& is, int size, int version) = 0;

    virtual void copyValueFrom (const Attribute& other) = 0;

    //------------------
    // Attribute factory
    //------------------

    IMF_EXPORT static Attribute* newAttribute (const char typeName[]);

    //-----------------------------------------------------------
    // Test if a given attribute type has already been registered
    //-----------------------------------------------------------

    IMF_EXPORT static bool knownType (const char typeName[]);

protected:
    //--------------------------------------------------
    // Register an attribute type so that newAttribute()
    // knows how to make objects of this type.
    //--------------------------------------------------
    IMF_EXPORT
    static void registerAttributeType (
        const char typeName[], Attribute* (*newAttribute) ());

    //------------------------------------------------------
    // Un-register an attribute type so that newAttribute()
    // no longer knows how to make objects of this type (for
    // debugging only).
    //------------------------------------------------------
    IMF_EXPORT
    static void unRegisterAttributeType (const char typeName[]);
};

//-------------------------------------------------
// Class template for attributes of a specific type
//-------------------------------------------------

template <class T>
class IMF_EXPORT_TEMPLATE_TYPE TypedAttribute : public Attribute
{
public:
    //------------------------------------------------------------
    // Constructors and destructor: default behavior. This assumes
    // that the type T is copyable/assignable/moveable.
    //------------------------------------------------------------

    TypedAttribute () = default;
    TypedAttribute (const T& value);
    TypedAttribute (const TypedAttribute<T>& other) = default;
    TypedAttribute (TypedAttribute<T>&& other)      = default;
    //NB: if we use a default destructor, it wreaks havoc with where the vtable and such end up
    //at least under mingw+windows, and since we are providing extern template instantiations
    //this will be pretty trim and should reduce code bloat
    virtual ~TypedAttribute ();

    TypedAttribute& operator= (const TypedAttribute<T>& other) = default;
    TypedAttribute& operator= (TypedAttribute<T>&& other) = default;

    //--------------------------------
    // Access to the attribute's value
    //--------------------------------

    T&       value ();
    const T& value () const;

    //--------------------------------
    // Get this attribute's type name.
    //--------------------------------

    virtual const char* typeName () const;

    //---------------------------------------------------------
    // Static version of typeName()
    // This function must be specialized for each value type T.
    //---------------------------------------------------------

    static const char* staticTypeName ();

    //---------------------
    // Make a new attribute
    //---------------------

    static Attribute* makeNewAttribute ();

    //------------------------------
    // Make a copy of this attribute
    //------------------------------

    virtual Attribute* copy () const;

    //-----------------------------------------------------------------
    // Type-specific attribute I/O and copying.
    // Depending on type T, these functions may have to be specialized.
    //-----------------------------------------------------------------

    virtual void writeValueTo (
        OPENEXR_IMF_INTERNAL_NAMESPACE::OStream& os, int version) const;

    virtual void readValueFrom (
        OPENEXR_IMF_INTERNAL_NAMESPACE::IStream& is, int size, int version);

    virtual void copyValueFrom (const Attribute& other);

    //------------------------------------------------------------
    // Dynamic casts that throw exceptions instead of returning 0.
    //------------------------------------------------------------

    static TypedAttribute*       cast (Attribute* attribute);
    static const TypedAttribute* cast (const Attribute* attribute);
    static TypedAttribute&       cast (Attribute& attribute);
    static const TypedAttribute& cast (const Attribute& attribute);

    //---------------------------------------------------------------
    // Register this attribute type so that Attribute::newAttribute()
    // knows how to make objects of this type.
    //
    // Note that this function is not thread-safe because it modifies
    // a global variable in the IlmIlm library.  A thread in a multi-
    // threaded program may call registerAttributeType() only when no
    // other thread is accessing any functions or classes in the
    // OpenEXR library.
    //
    //---------------------------------------------------------------

    static void registerAttributeType ();

    //-----------------------------------------------------
    // Un-register this attribute type (for debugging only)
    //-----------------------------------------------------

    static void unRegisterAttributeType ();

private:
    T _value;
};

//------------------------------------
// Implementation of TypedAttribute<T>
//------------------------------------

template <class T>
TypedAttribute<T>::TypedAttribute (const T& value)
    : Attribute (), _value (value)
{
    // empty
}

template <class T> TypedAttribute<T>::~TypedAttribute ()
{
    // empty
}

template <class T>
inline T&
TypedAttribute<T>::value ()
{
    return _value;
}

template <class T>
inline const T&
TypedAttribute<T>::value () const
{
    return _value;
}

template <class T>
const char*
TypedAttribute<T>::typeName () const
{
    return staticTypeName ();
}

template <class T>
Attribute*
TypedAttribute<T>::makeNewAttribute ()
{
    return new TypedAttribute<T> ();
}

template <class T>
Attribute*
TypedAttribute<T>::copy () const
{
    Attribute* attribute = new TypedAttribute<T> ();
    attribute->copyValueFrom (*this);
    return attribute;
}

template <class T>
void
TypedAttribute<T>::writeValueTo (
    OPENEXR_IMF_INTERNAL_NAMESPACE::OStream& os, int version) const
{
    OPENEXR_IMF_INTERNAL_NAMESPACE::Xdr::write<
        OPENEXR_IMF_INTERNAL_NAMESPACE::StreamIO> (os, _value);
}

template <class T>
void
TypedAttribute<T>::readValueFrom (
    OPENEXR_IMF_INTERNAL_NAMESPACE::IStream& is, int size, int version)
{
    OPENEXR_IMF_INTERNAL_NAMESPACE::Xdr::read<
        OPENEXR_IMF_INTERNAL_NAMESPACE::StreamIO> (is, _value);
}

template <class T>
void
TypedAttribute<T>::copyValueFrom (const Attribute& other)
{
    _value = cast (other)._value;
}

template <class T>
TypedAttribute<T>*
TypedAttribute<T>::cast (Attribute* attribute)
{
    TypedAttribute<T>* t = dynamic_cast<TypedAttribute<T>*> (attribute);

    if (t == 0) throw IEX_NAMESPACE::TypeExc ("Unexpected attribute type.");

    return t;
}

template <class T>
const TypedAttribute<T>*
TypedAttribute<T>::cast (const Attribute* attribute)
{
    const TypedAttribute<T>* t =
        dynamic_cast<const TypedAttribute<T>*> (attribute);

    if (t == 0) throw IEX_NAMESPACE::TypeExc ("Unexpected attribute type.");

    return t;
}

template <class T>
inline TypedAttribute<T>&
TypedAttribute<T>::cast (Attribute& attribute)
{
    return *cast (&attribute);
}

template <class T>
inline const TypedAttribute<T>&
TypedAttribute<T>::cast (const Attribute& attribute)
{
    return *cast (&attribute);
}

template <class T>
inline void
TypedAttribute<T>::registerAttributeType ()
{
    Attribute::registerAttributeType (staticTypeName (), makeNewAttribute);
}

template <class T>
inline void
TypedAttribute<T>::unRegisterAttributeType ()
{
    Attribute::unRegisterAttributeType (staticTypeName ());
}

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT

#if defined(_MSC_VER)
#    pragma warning(pop)
#endif

#endif