axmol/core/renderer/backend/Buffer.h

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 Copyright (c) 2018-2019 Xiamen Yaji Software Co., Ltd.

 https://axmolengine.github.io/

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#pragma once

#include "Macros.h"
#include "Types.h"
#include "base/Ref.h"

NS_AX_BEGIN

class MeshVertexData;
class MeshIndexData;
NS_AX_END  // namespace ax

NS_AX_BACKEND_BEGIN

/**
 * @addtogroup _backend
 * @{
 */

/**
 * @brief Used to store vertex and index data data.
 */
class Buffer : public ax::Ref
{
public:
    /**
     * @brief Update buffer data
     * @param data Specifies a pointer to data that will be copied into the data store for initialization.
     * @param size Specifies the size in bytes of the data store region being replaced.
     * @see `updateSubData(void* data, unsigned int offset, unsigned int size)`
     */
    virtual void updateData(const void* data, std::size_t size) = 0;

    /**
     * @brief Update buffer sub-region data
     * @param data Specifies a pointer to the new data that will be copied into the data store.
     * @param offset Specifies the offset into the buffer object's data store where data replacement will begin,
     * measured in bytes.
     * @param size Specifies the size in bytes of the data store region being replaced.
     * @see `updateData(void* data, unsigned int size)`
     */
    virtual void updateSubData(const void* data, std::size_t offset, std::size_t size) = 0;

    /**
     * By default, static buffer data will automatically stored when it comes to foreground.
     * This function is used to indicate whether external data needs to be used to update the buffer instead of using
     * the default stored data.
     * @param needDefaultStoredData Specifies whether to use the default stored data.
     */
    virtual void usingDefaultStoredData(bool needDefaultStoredData) = 0;

    /**
     * Get buffer size in bytes.
     * @return The buffer size in bytes.
     */
    std::size_t getSize() const { return _size; }

protected:
    /**
     * @param size Specifies the size in bytes of the buffer object's new data store.
     * @param type Specifies the target buffer object. The symbolic constant must be BufferType::VERTEX or
     * BufferType::INDEX.
     * @param usage Specifies the expected usage pattern of the data store. The symbolic constant must be
     * GL_STREAM_DRAW, GL_STATIC_DRAW, or GL_DYNAMIC_DRAW.
     */
    Buffer(std::size_t size, BufferType type, BufferUsage usage) : _usage(usage), _type(type), _size(size) {}

    virtual ~Buffer() = default;

    BufferUsage _usage = BufferUsage::DYNAMIC;  ///< Buffer usage.
    BufferType _type   = BufferType::VERTEX;    ///< Buffer type.
    std::size_t _size  = 0;                     ///< buffer size in bytes.
};

// end of _backend group
/// @}
NS_AX_BACKEND_END