magnum/src/Buffer.h

#ifndef Magnum_Buffer_h
#define Magnum_Buffer_h
/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013 Vladimír Vondruš <mosra@centrum.cz>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

/** @file
 * @brief Class Magnum::Buffer
 */

#include <cstddef>
#include <array>
#include <vector>
#include <Containers/EnumSet.h>

#include "Magnum.h"
#include "OpenGL.h"
#include "magnumVisibility.h"

namespace Magnum {

/**
@brief %Buffer

Encapsulates one OpenGL buffer object and provides functions for convenient
data updates.

@section Buffer-data Data updating

Default way to set or update buffer data with setData() or setSubData() is to
explicitly specify data size and pass the pointer to it:
@code
Buffer buffer;
Vector3* data = new Vector3[200];
buffer.setData(200*sizeof(Vector3), data, Buffer::Usage::StaticDraw);
@endcode
Howewer, in some cases, you have the data in fixed-size array with size known
at compile time. There is an convenient overload which detects the size of
passed array, so you don't have to repeat it:
@code
Vector3 data[] = {
    // ...
};
buffer.setData(data, Buffer::Usage::StaticDraw);
@endcode
There is also overload for array-like containers from STL, such as `std::vector` or
`std::array`:
@code
std::vector<Vector3> data;
buffer.setData(data, Buffer::Usage::StaticDraw);
@endcode

@subsection Buffer-data-mapping Memory mapping

%Buffer data can be also updated asynchronously. First you need to allocate
the buffer to desired size by passing `nullptr` to setData(), e.g.:
@code
buffer.setData(200*sizeof(Vector3)), nullptr, Buffer::Usage::StaticDraw);
@endcode
Then you can map the buffer to client memory and operate with the memory
directly. After you are done with the operation, call unmap() to unmap the
buffer again.
@code
Vector3* data = static_cast<Vector3*>(buffer.map(0, 200*sizeof(Vector3), Buffer::MapFlag::Write|Buffer::MapFlag::InvalidateBuffer));
for(std::size_t i = 0; i != 200; ++i)
    data[i] = ...;
CORRADE_INTERNAL_ASSERT_OUTPUT(buffer.unmap());
@endcode
If you are updating only a few discrete portions of the buffer, you can use
@ref MapFlag "MapFlag::FlushExplicit" and flushMappedRange() to reduce number
of memory operations performed by OpenGL on unmapping. Example:
@code
Vector3* data = static_cast<Vector3*>(buffer.map(0, 200*sizeof(Vector3), Buffer::MapFlag::Write|Buffer::MapFlag::FlushExplicit));
for(std::size_t i: {7, 27, 56, 128}) {
    data[i] = ...;
    buffer.flushMappedRange(i*sizeof(Vector3), sizeof(Vector3));
}
CORRADE_INTERNAL_ASSERT_OUTPUT(buffer.unmap());
@endcode

@section Buffer-performance-optimization Performance optimizations

The engine tracks currently bound buffers to avoid unnecessary calls to
@fn_gl{BindBuffer}. If the buffer is already bound to some target, functions
copy(), setData(), setSubData(), map(), flushMappedRange() and unmap() use
that target instead of binding the buffer to some specific target. You can
also use setTargetHint() to possibly reduce unnecessary rebinding.

If extension @extension{EXT,direct_state_access} is available, functions
copy(), setData(), setSubData(), map(), flushMappedRange() and unmap() use DSA
functions to avoid unnecessary calls to @fn_gl{BindBuffer}. See their
respective documentation for more information.

You can use functions invalidateData() and invalidateSubData() if you don't
need buffer data anymore to avoid unnecessary memory operations performed by
OpenGL in order to preserve the data. If running on OpenGL ES or extension
@extension{ARB,invalidate_subdata} is not available, these functions do
nothing.

@todo Support for AMD's query buffer (@extension{AMD,query_buffer_object})
@todo BindBufferRange/BindBufferOffset/BindBufferBase for transform feedback (3.0, @extension{EXT,transform_feedback})
 */
class MAGNUM_EXPORT Buffer {
    friend class Context;

    Buffer(const Buffer&) = delete;
    Buffer(Buffer&&) = delete;
    Buffer& operator=(const Buffer&) = delete;
    Buffer& operator=(Buffer&&) = delete;

    public:
        /**
         * @brief %Buffer target
         *
         * @see bind(Target), unbind(Target)
         */
        enum class Target: GLenum {
            /** Used for storing vertex attributes. */
            Array = GL_ARRAY_BUFFER,

            #ifndef MAGNUM_TARGET_GLES
            /**
             * Used for storing atomic counters.
             * @requires_gl42 %Extension @extension{ARB,shader_atomic_counters}
             * @requires_gl Atomic counters are not available in OpenGL ES.
             */
            AtomicCounter = GL_ATOMIC_COUNTER_BUFFER,
            #endif

            #ifndef MAGNUM_TARGET_GLES2
            /**
             * Source for copies. See copy().
             * @requires_gl31 %Extension @extension{ARB,copy_buffer}
             * @requires_gles30 Buffer copying is not available in OpenGL ES
             *      2.0.
             */
            CopyRead = GL_COPY_READ_BUFFER,

            /**
             * Target for copies. See copy().
             * @requires_gl31 %Extension @extension{ARB,copy_buffer}
             * @requires_gles30 Buffer copying is not available in OpenGL ES
             *      2.0.
             */
            CopyWrite = GL_COPY_WRITE_BUFFER,
            #endif

            #ifndef MAGNUM_TARGET_GLES
            /**
             * Indirect compute dispatch commands.
             * @requires_gl43 %Extension @extension{ARB,compute_shader}
             * @requires_gl Compute shaders are not available in OpenGL ES.
             */
            DispatchIndirect = GL_DISPATCH_INDIRECT_BUFFER,

            /**
             * Used for supplying arguments for indirect drawing.
             * @requires_gl40 %Extension @extension{ARB,draw_indirect}
             * @requires_gl Indirect drawing not available in OpenGL ES.
             */
            DrawIndirect = GL_DRAW_INDIRECT_BUFFER,
            #endif

            /** Used for storing vertex indices. */
            ElementArray = GL_ELEMENT_ARRAY_BUFFER

            #ifndef MAGNUM_TARGET_GLES2
            ,

            /**
             * Target for pixel pack operations.
             * @requires_gles30 Pixel buffer objects are not available in
             *      OpenGL ES 2.0.
             */
            PixelPack = GL_PIXEL_PACK_BUFFER,

            /**
             * Source for texture update operations.
             * @requires_gles30 Pixel buffer objects are not available in
             *      OpenGL ES 2.0.
             */
            PixelUnpack = GL_PIXEL_UNPACK_BUFFER,
            #endif

            #ifndef MAGNUM_TARGET_GLES
            /**
             * Used for shader storage.
             * @requires_gl43 %Extension @extension{ARB,shader_storage_buffer_object}
             * @requires_gl Shader storage is not available in OpenGL ES.
             */
            ShaderStorage = GL_SHADER_STORAGE_BUFFER,

            /**
             * Source for texel fetches. See BufferTexture.
             * @requires_gl31 %Extension @extension{ARB,texture_buffer_object}
             * @requires_gl Texture buffers are not available in OpenGL ES.
             */
            Texture = GL_TEXTURE_BUFFER,
            #endif

            #ifndef MAGNUM_TARGET_GLES2
            /**
             * Target for transform feedback.
             * @requires_gl30 %Extension @extension{EXT,transform_feedback}
             * @requires_gles30 Transform feedback is not available in OpenGL
             *      ES 2.0.
             */
            TransformFeedback = GL_TRANSFORM_FEEDBACK_BUFFER,

            /**
             * Used for storing uniforms.
             * @requires_gl31 %Extension @extension{ARB,uniform_buffer_object}
             * @requires_gles30 Uniform buffers are not available in OpenGL ES
             *      2.0.
             */
            Uniform = GL_UNIFORM_BUFFER
            #endif
        };

        /**
         * @brief %Buffer usage
         *
         * @see setData(GLsizeiptr, const GLvoid*, Usage)
         */
        enum class Usage: GLenum {
            /**
             * Set once by the application and used infrequently for drawing.
             */
            StreamDraw = GL_STREAM_DRAW,

            #ifndef MAGNUM_TARGET_GLES2
            /**
             * Set once as output from an OpenGL command and used infequently
             * for drawing.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::StreamDraw"
             *      is available in OpenGL ES 2.0.
             */
            StreamRead = GL_STREAM_READ,

            /**
             * Set once as output from an OpenGL command and used infrequently
             * for drawing or copying to other buffers.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::StreamDraw"
             *      is available in OpenGL ES 2.0.
             */
            StreamCopy = GL_STREAM_COPY,
            #endif

            /**
             * Set once by the application and used frequently for drawing.
             */
            StaticDraw = GL_STATIC_DRAW,

            #ifndef MAGNUM_TARGET_GLES2
            /**
             * Set once as output from an OpenGL command and queried many
             * times by the application.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::StaticDraw"
             *      is available in OpenGL ES 2.0.
             */
            StaticRead = GL_STATIC_READ,

            /**
             * Set once as output from an OpenGL command and used frequently
             * for drawing or copying to other buffers.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::StaticDraw"
             *      is available in OpenGL ES 2.0.
             */
            StaticCopy = GL_STATIC_COPY,
            #endif

            /**
             * Updated frequently by the application and used frequently
             * for drawing or copying to other images.
             */
            DynamicDraw = GL_DYNAMIC_DRAW

            #ifndef MAGNUM_TARGET_GLES2
            ,

            /**
             * Updated frequently as output from OpenGL command and queried
             * many times from the application.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::DynamicDraw"
             *      is available in OpenGL ES 2.0.
             */
            DynamicRead = GL_DYNAMIC_READ,

            /**
             * Updated frequently as output from OpenGL command and used
             * frequently for drawing or copying to other images.
             * @requires_gles30 Only @ref Magnum::Buffer::Usage "Usage::DynamicDraw"
             *      is available in OpenGL ES 2.0.
             */
            DynamicCopy = GL_DYNAMIC_COPY
            #endif
        };

        #ifndef MAGNUM_TARGET_GLES3
        /**
         * @brief Memory mapping access
         *
         * @deprecated Prefer to use @ref Magnum::Buffer::map(GLintptr, GLsizeiptr, MapFlags) "map(GLintptr, GLsizeiptr, MapFlags)"
         *      instead, as it has more complete set of features.
         * @see map(MapAccess)
         * @requires_es_extension %Extension @es_extension{OES,mapbuffer} in
         *      OpenGL ES 2.0, use @ref Magnum::Buffer::map(GLintptr, GLsizeiptr, MapFlags) "map(GLintptr, GLsizeiptr, MapFlags)"
         *      in OpenGL ES 3.0 instead.
         */
        enum class MapAccess: GLenum {
            #ifndef MAGNUM_TARGET_GLES
            /**
             * Map buffer for reading only.
             * @requires_gl Only @ref Magnum::Buffer::MapAccess "MapAccess::WriteOnly"
             *      is available in OpenGL ES 2.0.
             */
            ReadOnly = GL_READ_ONLY,
            #endif

            /**
             * Map buffer for writing only.
             */
            #ifdef MAGNUM_TARGET_GLES
            WriteOnly = GL_WRITE_ONLY_OES
            #else
            WriteOnly = GL_WRITE_ONLY,

            /**
             * Map buffer for both reading and writing.
             * @requires_gl Only @ref Magnum::Buffer::MapAccess "MapAccess::WriteOnly"
             *      is available in OpenGL ES 2.0.
             */
            ReadWrite = GL_READ_WRITE
            #endif
        };
        #endif

        /**
         * @brief Memory mapping flag
         *
         * @see MapFlags, map(GLintptr, GLsizeiptr, MapFlags)
         * @requires_gl30 %Extension @extension{ARB,map_buffer_range}
         * @requires_gles30 %Extension @es_extension{EXT,map_buffer_range}
         */
        enum class MapFlag: GLbitfield {
            /** Map buffer for reading. */
            #ifndef MAGNUM_TARGET_GLES2
            Read = GL_MAP_READ_BIT,
            #else
            Read = GL_MAP_READ_BIT_EXT,
            #endif

            /** Map buffer for writing. */
            #ifndef MAGNUM_TARGET_GLES2
            Write = GL_MAP_WRITE_BIT,
            #else
            Write = GL_MAP_WRITE_BIT_EXT,
            #endif

            /**
             * Previous contents of the entire buffer may be discarded. May
             * not be used in combination with @ref MapFlag "MapFlag::Read".
             * @see invalidateData()
             */
            #ifndef MAGNUM_TARGET_GLES2
            InvalidateBuffer = GL_MAP_INVALIDATE_BUFFER_BIT,
            #else
            InvalidateBuffer = GL_MAP_INVALIDATE_BUFFER_BIT_EXT,
            #endif

            /**
             * Previous contents of mapped range may be discarded. May not
             * be used in combination with @ref MapFlag "MapFlag::Read".
             * @see invalidateSubData()
             */
            #ifndef MAGNUM_TARGET_GLES2
            InvalidateRange = GL_MAP_INVALIDATE_RANGE_BIT,
            #else
            InvalidateRange = GL_MAP_INVALIDATE_RANGE_BIT_EXT,
            #endif

            /**
             * Only one or more discrete subranges of the mapping will be
             * modified. See flushMappedRange() for more information. May only
             * be used in conjuction with @ref MapFlag "MapFlag::Write".
             */
            #ifndef MAGNUM_TARGET_GLES2
            FlushExplicit = GL_MAP_FLUSH_EXPLICIT_BIT,
            #else
            FlushExplicit = GL_MAP_FLUSH_EXPLICIT_BIT_EXT,
            #endif

            /**
             * No pending operations on the buffer should be synchronized
             * before mapping.
             */
            #ifndef MAGNUM_TARGET_GLES2
            Unsynchronized = GL_MAP_UNSYNCHRONIZED_BIT
            #else
            Unsynchronized = GL_MAP_UNSYNCHRONIZED_BIT_EXT
            #endif
        };

        /**
         * @brief Memory mapping flags
         *
         * @see map(GLintptr, GLsizeiptr, MapFlags)
         * @requires_gl30 %Extension @extension{ARB,map_buffer_range}
         * @requires_gles30 %Extension @es_extension{EXT,map_buffer_range}
         */
        typedef Corrade::Containers::EnumSet<MapFlag, GLbitfield> MapFlags;

        /**
         * @brief Unbind any buffer from given target
         * @param target    %Target
         *
         * @see @fn_gl{BindBuffer}
         */
        inline static void unbind(Target target) { bind(target, 0); }

        #ifndef MAGNUM_TARGET_GLES2
        /**
         * @brief Copy one buffer to another
         * @param read          %Buffer from which to read
         * @param write         %Buffer to which to copy
         * @param readOffset    Offset in the read buffer
         * @param writeOffset   Offset in the write buffer
         * @param size          Data size
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffers aren't already bound somewhere, they are bound to
         * `Target::CopyRead` and `Target::CopyWrite` before the copy is
         * performed.
         * @see @fn_gl{BindBuffer} and @fn_gl{CopyBufferSubData} or
         *      @fn_gl_extension{NamedCopyBufferSubData,EXT,direct_state_access}
         * @requires_gl31 %Extension @extension{ARB,copy_buffer}
         * @requires_gles30 %Buffer copying is not available in OpenGL ES 2.0.
         */
        inline static void copy(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size) {
            copyImplementation(read, write, readOffset, writeOffset, size);
        }
        #endif

        /**
         * @brief Constructor
         * @param targetHint    Target hint, see setTargetHint() for more
         *      information
         *
         * Generates new OpenGL buffer.
         * @see @fn_gl{GenBuffers}
         */
        inline explicit Buffer(Target targetHint = Target::Array): _targetHint(targetHint) {
            glGenBuffers(1, &_id);
        }

        /**
         * @brief Destructor
         *
         * Deletes associated OpenGL buffer.
         * @see @fn_gl{DeleteBuffers}
         */
        virtual ~Buffer();

        /** @brief OpenGL buffer ID */
        inline GLuint id() const { return _id; }

        /** @brief Target hint */
        inline Target targetHint() const { return _targetHint; }

        /**
         * @brief Set target hint
         *
         * If @extension{EXT,direct_state_access} is not available, the buffer
         * must be internally bound to some target before any operation. You
         * can specify target which will always be used when binding the
         * buffer internally, possibly saving some calls to @fn_gl{BindBuffer}.
         *
         * Default target hint is `Target::Array`.
         * @see setData(), setSubData()
         * @todo Target::ElementArray cannot be used when no VAO is bound -
         *      http://www.opengl.org/wiki/Vertex_Specification#Index_buffers
         *      ... damned GL state
         */
        inline void setTargetHint(Target hint) { _targetHint = hint; }

        /**
         * @brief Bind buffer
         * @param target    %Target
         *
         * @todo Allow binding to Target::ElementArray only if VAO is bound
         *      to avoid potential issues?
         * @bug Binding to ElementArray if any VAO is active will corrupt the mesh
         * @todo Don't allow user to bind buffers?
         * @see @fn_gl{BindBuffer}
         */
        inline void bind(Target target) { bind(target, _id); }

        /**
         * @brief Set buffer data
         * @param size      Data size
         * @param data      Pointer to data
         * @param usage     %Buffer usage
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffer is not already bound somewhere, it is bound to hinted target
         * before the operation.
         * @see setTargetHint(), @fn_gl{BindBuffer} and @fn_gl{BufferData} or
         *      @fn_gl_extension{NamedBufferData,EXT,direct_state_access}
         */
        inline void setData(GLsizeiptr size, const GLvoid* data, Usage usage) {
            (this->*setDataImplementation)(size, data, usage);
        }

        /**
         * @brief Set buffer data
         * @param data      Fixed-size array with data
         * @param usage     %Buffer usage
         *
         * @see setData(GLsizeiptr, const GLvoid*, Usage).
         */
        template<std::size_t size, class T> inline void setData(const T(&data)[size], Usage usage) {
            setData(size*sizeof(T), data, usage);
        }

        /**
         * @brief Set buffer data
         * @param data      Vector with data
         * @param usage     %Buffer usage
         *
         * @see setData(GLsizeiptr, const GLvoid*, Usage)
         */
        template<class T> inline void setData(const std::vector<T>& data, Usage usage) {
            setData(data.size()*sizeof(T), data.data(), usage);
        }

        /** @overload */
        template<std::size_t size, class T> inline void setData(const std::array<T, size>& data, Usage usage) {
            setData(data.size()*sizeof(T), data.data(), usage);
        }

        /**
         * @brief Set buffer subdata
         * @param offset    Offset in the buffer
         * @param size      Data size
         * @param data      Pointer to data
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffer is not already bound somewhere, it is bound to hinted target
         * before the operation.
         * @see setTargetHint(), @fn_gl{BindBuffer} and @fn_gl{BufferSubData}
         *      or @fn_gl_extension{NamedBufferSubData,EXT,direct_state_access}
         */
        inline void setSubData(GLintptr offset, GLsizeiptr size, const GLvoid* data) {
            (this->*setSubDataImplementation)(offset, size, data);
        }

        /**
         * @brief Set buffer subdata
         * @param offset    Offset in the buffer
         * @param data      Fixed-size array with data
         *
         * @see setSubData(GLintptr, GLsizeiptr, const GLvoid*)
         */
        template<std::size_t size, class T> inline void setSubData(GLintptr offset, const T(&data)[size]) {
            setSubData(offset, size*sizeof(T), data);
        }

        /**
         * @brief Set buffer subdata
         * @param offset    Offset in the buffer
         * @param data      Vector with data
         *
         * @see setSubData(GLintptr, GLsizeiptr, const GLvoid*)
         */
        template<class T> inline void setSubData(GLintptr offset, const std::vector<T>& data) {
            setSubData(offset, data.size()*sizeof(T), data.data());
        }

        /** @overload */
        template<std::size_t size, class T> inline void setSubData(GLintptr offset, const std::array<T, size>& data) {
            setSubData(offset, data.size()*sizeof(T), data.data());
        }

        #ifndef MAGNUM_TARGET_GLES
        /**
         * @brief Invalidate buffer data
         *
         * If running on OpenGL ES or extension @extension{ARB,invalidate_subdata}
         * is not available, this function does nothing.
         * @see @ref MapFlag "MapFlag::InvalidateBuffer", @fn_gl{InvalidateBufferData}
         */
        inline void invalidateData() {
            (this->*invalidateImplementation)();
        }

        /**
         * @brief Invalidate buffer subdata
         * @param offset    Offset into the buffer
         * @param length    Length of the invalidated range
         *
         * If running on OpenGL ES or extension @extension{ARB,invalidate_subdata}
         * is not available, this function does nothing.
         * @see @ref MapFlag "MapFlag::InvalidateRange", @fn_gl{InvalidateBufferData}
         */
        inline void invalidateSubData(GLintptr offset, GLsizeiptr length) {
            (this->*invalidateSubImplementation)(offset, length);
        }
        #endif

        #ifndef MAGNUM_TARGET_GLES3
        /**
         * @brief Map buffer to client memory
         * @param access    Access
         * @return Pointer to buffer data
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffer is not already bound somewhere, it is bound to hinted target
         * before the operation.
         * @deprecated Prefer to use @ref Magnum::Buffer::map(GLintptr, GLsizeiptr, MapFlags) "map(GLintptr, GLsizeiptr, MapFlags)"
         *      instead, as it has more complete set of features.
         * @see unmap(), setTargetHint(), @fn_gl{BindBuffer} and @fn_gl{MapBuffer}
         *      or @fn_gl_extension{MapNamedBuffer,EXT,direct_state_access}
         * @requires_es_extension %Extension @es_extension{OES,mapbuffer} in
         *      OpenGL ES 2.0, use @ref Magnum::Buffer::map(GLintptr, GLsizeiptr, MapFlags) "map(GLintptr, GLsizeiptr, MapFlags)"
         *      in OpenGL ES 3.0 instead.
         */
        inline void* map(MapAccess access) {
            return (this->*mapImplementation)(access);
        }
        #endif

        /**
         * @brief Map buffer to client memory
         * @param offset    Offset into the buffer
         * @param length    Length of the mapped memory
         * @param flags     Flags. At least @ref MapFlag "MapFlag::Read" or
         *      @ref MapFlag "MapFlag::Write" must be specified.
         * @return Pointer to buffer data
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffer is not already bound somewhere, it is bound to hinted target
         * before the operation.
         * @see flushMappedRange(), unmap(), map(MapAccess), setTargetHint(), @fn_gl{BindBuffer}
         *      and @fn_gl{MapBufferRange} or @fn_gl_extension{MapNamedBufferRange,EXT,direct_state_access}
         * @requires_gl30 %Extension @extension{ARB,map_buffer_range}
         * @requires_gles30 %Extension @es_extension{EXT,map_buffer_range}
         */
        inline void* map(GLintptr offset, GLsizeiptr length, MapFlags flags) {
            return (this->*mapRangeImplementation)(offset, length, flags);
        }

        /**
         * @brief Flush mapped range
         * @param offset    Offset relative to start of mapped range
         * @param length    Length of the flushed memory
         *
         * Flushes specified subsection of mapped range. Use only if you called
         * map() with @ref MapFlag "MapFlag::FlushExplicit" flag. See
         * @ref Buffer-data-mapping "class documentation" for usage example.
         *
         * If @extension{EXT,direct_state_access} is not available and the
         * buffer is not already bound somewhere, it is bound to hinted target
         * before the operation.
         * @see setTargetHint(), @fn_gl{BindBuffer} and @fn_gl{FlushMappedBufferRange}
         *      or @fn_gl_extension{FlushMappedNamedBufferRange,EXT,direct_state_access}
         * @requires_gl30 %Extension @extension{ARB,map_buffer_range}
         * @requires_gles30 %Extension @es_extension{EXT,map_buffer_range}
         */
        inline void flushMappedRange(GLintptr offset, GLsizeiptr length) {
            (this->*flushMappedRangeImplementation)(offset, length);
        }

        /**
         * @brief Unmap buffer
         * @return `False` if the data have become corrupt during the time
         *      the buffer was mapped (e.g. after screen was resized), `true`
         *      otherwise.
         *
         * Unmaps buffer previously mapped with map(), invalidating the
         * pointer returned by these functions. If @extension{EXT,direct_state_access}
         * is not available and the buffer is not already bound somewhere, it
         * is bound to hinted target before the operation.
         * @see setTargetHint(), @fn_gl{BindBuffer} and @fn_gl{UnmapBuffer} or
         *      @fn_gl_extension{UnmapNamedBuffer,EXT,direct_state_access}
         * @requires_gles30 %Extension @es_extension{OES,mapbuffer}
         */
        inline bool unmap() {
            return (this->*unmapImplementation)();
        }

    private:
        static void MAGNUM_LOCAL initializeContextBasedFunctionality(Context* context);

        static void bind(Target hint, GLuint id);
        Target MAGNUM_LOCAL bindInternal(Target hint);

        #ifndef MAGNUM_TARGET_GLES2
        typedef void(*CopyImplementation)(Buffer*, Buffer*, GLintptr, GLintptr, GLsizeiptr);
        static void MAGNUM_LOCAL copyImplementationDefault(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size);
        #ifndef MAGNUM_TARGET_GLES
        static void MAGNUM_LOCAL copyImplementationDSA(Buffer* read, Buffer* write, GLintptr readOffset, GLintptr writeOffset, GLsizeiptr size);
        #endif
        static CopyImplementation copyImplementation;
        #endif

        typedef void(Buffer::*SetDataImplementation)(GLsizeiptr, const GLvoid*, Usage);
        void MAGNUM_LOCAL setDataImplementationDefault(GLsizeiptr size, const GLvoid* data, Usage usage);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL setDataImplementationDSA(GLsizeiptr size, const GLvoid* data, Usage usage);
        #endif
        static SetDataImplementation setDataImplementation;

        typedef void(Buffer::*SetSubDataImplementation)(GLintptr, GLsizeiptr, const GLvoid*);
        void MAGNUM_LOCAL setSubDataImplementationDefault(GLintptr offset, GLsizeiptr size, const GLvoid* data);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL setSubDataImplementationDSA(GLintptr offset, GLsizeiptr size, const GLvoid* data);
        #endif
        static SetSubDataImplementation setSubDataImplementation;

        typedef void(Buffer::*InvalidateImplementation)();
        void MAGNUM_LOCAL invalidateImplementationNoOp();
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL invalidateImplementationARB();
        #endif
        static InvalidateImplementation invalidateImplementation;

        typedef void(Buffer::*InvalidateSubImplementation)(GLintptr, GLsizeiptr);
        void MAGNUM_LOCAL invalidateSubImplementationNoOp(GLintptr offset, GLsizeiptr length);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL invalidateSubImplementationARB(GLintptr offset, GLsizeiptr length);
        #endif
        static InvalidateSubImplementation invalidateSubImplementation;

        #ifndef MAGNUM_TARGET_GLES3
        typedef void*(Buffer::*MapImplementation)(MapAccess);
        void MAGNUM_LOCAL * mapImplementationDefault(MapAccess access);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL * mapImplementationDSA(MapAccess access);
        #endif
        static MapImplementation mapImplementation;
        #endif

        typedef void*(Buffer::*MapRangeImplementation)(GLintptr, GLsizeiptr, MapFlags);
        void MAGNUM_LOCAL * mapRangeImplementationDefault(GLintptr offset, GLsizeiptr length, MapFlags access);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL * mapRangeImplementationDSA(GLintptr offset, GLsizeiptr length, MapFlags access);
        #endif
        static MapRangeImplementation mapRangeImplementation;

        typedef void(Buffer::*FlushMappedRangeImplementation)(GLintptr, GLsizeiptr);
        void MAGNUM_LOCAL flushMappedRangeImplementationDefault(GLintptr offset, GLsizeiptr length);
        #ifndef MAGNUM_TARGET_GLES
        void MAGNUM_LOCAL flushMappedRangeImplementationDSA(GLintptr offset, GLsizeiptr length);
        #endif
        static FlushMappedRangeImplementation flushMappedRangeImplementation;

        typedef bool(Buffer::*UnmapImplementation)();
        bool MAGNUM_LOCAL unmapImplementationDefault();
        #ifndef MAGNUM_TARGET_GLES
        bool MAGNUM_LOCAL unmapImplementationDSA();
        #endif
        static UnmapImplementation unmapImplementation;

        GLuint _id;
        Target _targetHint;
};

CORRADE_ENUMSET_OPERATORS(Buffer::MapFlags)

/** @debugoperator{Magnum::Buffer} */
Debug MAGNUM_EXPORT operator<<(Debug debug, Buffer::Target value);

}

#endif