cocos-enhance-kit/cocos2d-x/cocos/renderer/gfx/IndexBuffer.h

/****************************************************************************
 Copyright (c) 2018 Xiamen Yaji Software Co., Ltd.

 http://www.cocos2d-x.org
 
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 of this software and associated documentation files (the "Software"), to deal
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#pragma once

#include <functional>
#include "../Macro.h"
#include "../Types.h"
#include "GraphicsHandle.h"

RENDERER_BEGIN

/**
 * @addtogroup gfx
 * @{
 */

class DeviceGraphics;

/**
 * IndexBuffer manages the GL buffer for element indices.
 * It creates, updates and destoies the GL buffer.
 */
class IndexBuffer final : public GraphicsHandle
{
public:
    /**
     * Creates an IndexBuffer object
     * @param[in] device DeviceGraphics pointer.
     * @param[in] format Index element format.
     * @param[in] usage The usage pattern of the index buffer.
     * @param[in] data Data pointer, could be nullptr, then nothing is updated to the buffer.
     * @param[in] dataByteLength Data's byte length.
     * @param[in] numIndices Count of indices.
     */
    RENDERER_DEFINE_CREATE_METHOD_6(IndexBuffer, init, DeviceGraphics*, IndexFormat, Usage, const void*, size_t, uint32_t)

    IndexBuffer();
    virtual ~IndexBuffer();

    /**
     * Initializes the index buffer with necessary options.
     * @param[in] device DeviceGraphics pointer.
     * @param[in] format Index element format.
     * @param[in] usage The usage pattern of the index buffer.
     * @param[in] data Data pointer, could be nullptr, then nothing is updated to the buffer.
     * @param[in] dataByteLength Data's byte length.
     * @param[in] numIndices Count of indices.
     */
    bool init(DeviceGraphics* device, IndexFormat format, Usage usage, const void* data, size_t dataByteLength, uint32_t numIndices);
    /**
     * Update data to the GL index buffer
     * @param[in] offset Destination offset for filling buffer data.
     * @param[in] data Data to be updated.
     * @param[in] dataByteLength Data byte length to be updated.
     */
    void update(uint32_t offset, const void* data, size_t dataByteLength);

    /**
     * Gets the count of indices.
     */
    inline uint32_t getCount() const { return _numIndices; }
    /**
     * Sets the count of indices.
     */
    inline void setCount(uint32_t numIndices) { _numIndices = numIndices; }

    /**
     * Gets the format of indices.
     */
    inline IndexFormat getFormat() const { return _format; }
    /**
     * Sets the format of indices.
     */
    inline void setFormat(IndexFormat format) { _format = format; }

    /**
     * Gets bytes occupied by each index.
     */
    inline uint32_t getBytesPerIndex() const { return _bytesPerIndex; }
    /**
     * Sets bytes occupied by each index.
     */
    inline void setBytesPerIndex(uint32_t bytesPerIndex) {_bytesPerIndex = bytesPerIndex; }

    /**
     * Gets usage pattern of the index buffer
     */
    inline Usage getUsage() const { return _usage; }
    /**
     * Sets usage pattern of the index buffer
     */
    inline void setUsage(Usage usage) { _usage = usage; }

    /**
     * Gets byte size of the index buffer
     */
    inline uint32_t getBytes() const { return _bytes; }

    using FetchDataCallback = std::function<uint8_t*(size_t*)>;
    void setFetchDataCallback(const FetchDataCallback& cb) { _fetchDataCallback = cb; }
    uint8_t* invokeFetchDataCallback(size_t* bytes) {
        if (_fetchDataCallback == nullptr)
        {
            *bytes = 0;
            return nullptr;
        }
        return _fetchDataCallback(bytes);
    }

    /**
     * Destroies the index buffer
     */
    void destroy();
    
private:
    DeviceGraphics* _device;
    IndexFormat _format;
    Usage _usage;
    uint32_t _numIndices;
    uint32_t _bytesPerIndex;
    uint32_t _bytes;
    bool _needExpandDataStore = true;

    FetchDataCallback _fetchDataCallback;

    CC_DISALLOW_COPY_ASSIGN_AND_MOVE(IndexBuffer)
};

// end of gfx group
/// @}

RENDERER_END