Availability.h

#pragma once
 
#include <CesiumGeometry/Library.h>
#include <CesiumUtility/Assert.h>
 
#include <cstdint>
#include <memory>
#include <optional>
#include <span>
#include <utility>
#include <variant>
#include <vector>
 
namespace CesiumGeometry {
 
namespace AvailabilityUtilities {
uint8_t countOnesInByte(uint8_t _byte);
uint32_t countOnesInBuffer(std::span<const std::byte> buffer);
} // namespace AvailabilityUtilities

struct CESIUMGEOMETRY_API ConstantAvailability {
  bool constant;
};

struct CESIUMGEOMETRY_API SubtreeBufferView {
  uint32_t byteOffset;
  uint32_t byteLength;
  uint8_t buffer;
};

typedef std::variant<ConstantAvailability, SubtreeBufferView> AvailabilityView;

struct CESIUMGEOMETRY_API AvailabilitySubtree {
  AvailabilityView tileAvailability;
  AvailabilityView contentAvailability;
  AvailabilityView subtreeAvailability;
  std::vector<std::vector<std::byte>> buffers;
};

struct CESIUMGEOMETRY_API AvailabilityNode {
  std::optional<AvailabilitySubtree> subtree;

  std::vector<std::unique_ptr<AvailabilityNode>> childNodes;

  AvailabilityNode() noexcept;

  void setLoadedSubtree(
      AvailabilitySubtree&& subtree_,
      uint32_t maxChildrenSubtrees) noexcept;
};

struct CESIUMGEOMETRY_API AvailabilityTree {
  std::unique_ptr<AvailabilityNode> pRoot;
};

class CESIUMGEOMETRY_API AvailabilityAccessor {
public:
  AvailabilityAccessor(
      const AvailabilityView& view,
      const AvailabilitySubtree& subtree) noexcept;

  bool isBufferView() const noexcept {
    return pBufferView != nullptr && bufferAccessor;
  }

  bool isConstant() const noexcept { return pConstant != nullptr; }

  bool getConstant() const { return pConstant->constant; }

  const std::span<const std::byte>& getBufferAccessor() const {
    CESIUM_ASSERT(bufferAccessor.has_value());
    return *bufferAccessor;
  }

  const std::byte& operator[](size_t i) const {
    CESIUM_ASSERT(bufferAccessor.has_value());
    return bufferAccessor.value()[i];
  }

  size_t size() const { return pBufferView->byteLength; }
 
private:
  const SubtreeBufferView* pBufferView;
  const ConstantAvailability* pConstant;
  std::optional<std::span<const std::byte>> bufferAccessor;
};
} // namespace CesiumGeometry