ImfAttribute.h

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//
// Copyright (c) 2004, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
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#ifndef INCLUDED_IMF_ATTRIBUTE_H
#define INCLUDED_IMF_ATTRIBUTE_H

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

#include "IexBaseExc.h"
#include "ImfIO.h"
#include "ImfXdr.h"
#include "ImfForward.h"
#include "ImfExport.h"
#include "ImfNamespace.h"

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER


class IMF_EXPORT Attribute
{
  public:

    //---------------------------
    // Constructor and destructor
    //---------------------------

    Attribute ();
    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
    //------------------

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


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

    static bool                 knownType (const char typeName[]);


  protected:

    //--------------------------------------------------
    // Register an attribute type so that newAttribute()
    // knows how to make objects of this type.
    //--------------------------------------------------

    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).
    //------------------------------------------------------

    static void         unRegisterAttributeType (const char typeName[]);
};


//-------------------------------------------------
// Class template for attributes of a specific type
//-------------------------------------------------
    
template <class T>
class TypedAttribute: public Attribute
{
  public:

    //----------------------------
    // Constructors and destructor
    //------------_---------------

    TypedAttribute ();
    TypedAttribute (const T &value);
    TypedAttribute (const TypedAttribute<T> &other);
    virtual ~TypedAttribute ();


    //--------------------------------
    // 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
    // IlmImf 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 ():
    Attribute (),
    _value (T())
{
    // empty
}


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


template <class T>
TypedAttribute<T>::TypedAttribute (const TypedAttribute<T> &other):
    Attribute (other),
    _value ()
{
    copyValueFrom (other);
}


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


#endif