StelVertexBufferBackend.hpp

/*
 * Stellarium
 * Copyright (C) 2012 Ferdinand Majerech
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335, USA.
 */

#ifndef _STELVERTEXBUFFERBACKEND_HPP_
#define _STELVERTEXBUFFERBACKEND_HPP_

#include <QVector>

#include "StelVertexAttribute.hpp"


static const int MAX_VERTEX_ATTRIBUTES = 8;

class StelVertexBufferBackend
{
    struct Attributes
    {
        StelVertexAttribute attributes[MAX_VERTEX_ATTRIBUTES];
        int sizes[MAX_VERTEX_ATTRIBUTES];
        int count;

        Attributes(const QVector<StelVertexAttribute>& attributeVector)
            : count(attributeVector.size())
        {
            for(int a = 0; a < count; ++a)
            {
                Q_ASSERT_X(count < MAX_VERTEX_ATTRIBUTES, Q_FUNC_INFO,
                           "Too many vertex attributes (increase MAX_VERTEX_ATTRIBUTES"
                           "in StelVertexBufferBackend.hpp)");
                attributes[a] = attributeVector[a];
                sizes[a]      = attributeSize(attributes[a].type);
            }
        }
    };

public:
    StelVertexBufferBackend(const QVector<StelVertexAttribute>& attributes)
        : attributes(attributes)
    {
    }

    virtual ~StelVertexBufferBackend(){};
    
    virtual void addVertex(const void* const vertexInPtr) = 0;
    
    virtual void getVertex(const int index, void* const vertexOutPtr) const = 0;
    
    virtual void setVertex(const int index, const void* const vertexInPtr) = 0;
    
    virtual void lock() = 0;
    
    virtual void unlock() = 0;
    
    virtual void clear() = 0;

    void validateVertexType(const int vertexSize)
    {
#ifdef NDEBUG
        Q_UNUSED(vertexSize);
#endif
        // We have no way of looking at each data member of the vertex type, 
        // but we can at least enforce that their total length matches.
        int bytes = 0;
        
        for(int attrib = 0; attrib < attributes.count; ++attrib)
        {
            bytes += attributes.sizes[attrib];
        }
        
        Q_ASSERT_X(bytes == vertexSize, Q_FUNC_INFO,
                   "Size of the vertex type in bytes doesn't match the sum of sizes of "
                   "all vertex attributes as reported by \"attributes\" data member.");
    }
    
protected:
    const Attributes attributes;
};


#endif // _STELVERTEXBUFFERBACKEND_HPP_