OpenSpace/modules/globebrowsing/other/pixelbuffer.h

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2017                                                               *
 *                                                                                       *
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#ifndef __OPENSPACE_MODULE_GLOBEBROWSING___PIXEL_BUFFER___H__
#define __OPENSPACE_MODULE_GLOBEBROWSING___PIXEL_BUFFER___H__

#include <ghoul/opengl/ghoul_gl.h>

namespace openspace {
namespace globebrowsing {

/**
 * Handles an OpenGL pixel buffer which contains data allocated on the GPU. A simple
 * class that wraps the standard functionality of OpenGL pixel buffer objects. Once
 * the PixelBuffer is created, data is allocated on the GPU. When mapping data to a
 * address pointer, the user needs to ensure the data is unmapped before the data can
 * be used on the GPU / CPU depending on Usage.
 */
class PixelBuffer
{
public:
    /**
     * All kinds of usage for pixel buffer objects as defined by the OpenGL standard.
     * See: https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBufferData.xhtml
     */
	enum class Usage {
		StreamDraw = GL_STREAM_DRAW,
		StreamRead = GL_STREAM_READ,
		StreamCopy = GL_STREAM_COPY,
		StaticDraw = GL_STATIC_DRAW,
		StaticRead = GL_STATIC_READ,
		StaticCopy = GL_STATIC_COPY,
		DynamicDraw = GL_DYNAMIC_DRAW,
		DynamicRead = GL_DYNAMIC_READ,
		DynamicCopy = GL_DYNAMIC_COPY
	};

    /**
     * Access hints for OpenGL buffer mapping
     * See: https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/glMapBuffer.xml
     */
    enum class Access {
        ReadOnly = GL_READ_ONLY,
        WriteOnly = GL_WRITE_ONLY,
        ReadWrite = GL_READ_WRITE
    };

    /**
     * Allocates <code>numBytes</code> bytes on the GPU and creates an ID for the pixel
     * buffer object.
     * \param numBytes is the number of bytes to be allocated on GPU memory
     * \param usage is the <code>Usage</code> for the pixel buffer
     */
    PixelBuffer(size_t numBytes, Usage usage);
    
    /**
     * calls glDeleteBuffers().
     */
    ~PixelBuffer();

    /**
     * Maps an address pointer to GPU direct memory access. The user must make sure the
     * buffer is bound before calling this function.
     * \param access is the access to which can be any of <code>GL_READ_ONLY</code>,
     * <code>GL_WRITE_ONLY</code>, or <code>GL_READ_WRITE</code>
     * \returns the DMA address to the mapped buffer. Returns nullptr if the mapping
     * failed
     */
    void* mapBuffer(Access access);
    
    /**
     * Maps an address pointer to GPU direct memory access. Gives access to a range of
     * the buffer. The user must make sure the buffer is bound before calling this
     * function.
     * \param offet is the number of bytes to the first address to get in the buffer
     * \param length is the number of bytes to access in the buffer
     * \param access is a bitfield describing the access as described in:
     * https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glMapBufferRange.xhtml
     * \returns the DMA address to the mapped buffer. Returns nullptr if the mapping
     * failed
     */
    void* mapBufferRange(GLintptr offset, GLsizeiptr length, GLbitfield access);

    /**
     * Maps the default buffer and makes the data available on the GPU
     */
    bool unMapBuffer();

    /**
     * Calls glBindBuffer()
     */
    void bind();

    /**
     * Calls glBindBuffer() with argument 0 to unmap any pixel buffer
     */
    void unbind();

    /**
     * \returns true of the buffer is mapped, otherwise false 
     */
    bool isMapped() const;

    /**
     * \returns the OpenGL id of the pixel buffer object
     */
    operator GLuint() const;

private:
    GLuint _id;
    const size_t _numBytes;
    const Usage _usage;
    bool _isMapped;
};

} // namespace globebrowsing
} // namespace openspace

#endif // __OPENSPACE_MODULE_GLOBEBROWSING___PIXEL_BUFFER___H__