StyleValueHandle.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#pragma once
 
#include <cstdint>
 
#include <yoga/Yoga.h>
 
#include <yoga/numeric/FloatOptional.h>
#include <yoga/style/SmallValueBuffer.h>
#include <yoga/style/StyleLength.h>
 
namespace facebook::yoga {
 
#pragma pack(push)
#pragma pack(1)
 
class StyleValueHandle {
 public:
  static constexpr StyleValueHandle ofAuto() {
    StyleValueHandle handle;
    handle.setType(Type::Auto);
    return handle;
  }
 
  constexpr bool isUndefined() const {
    return type() == Type::Undefined;
  }
 
  constexpr bool isDefined() const {
    return !isUndefined();
  }
 
  constexpr bool isAuto() const {
    return type() == Type::Auto;
  }
 
  constexpr bool isPercent() const {
    return type() == Type::Percent;
  }
 
  constexpr bool isPoint() const {
    return type() == Type::Point;
  }
 
 private:
  friend class StyleValuePool;
 
  static constexpr uint16_t kHandleTypeMask = 0b0000'0000'0000'0111;
  static constexpr uint16_t kHandleIndexedMask = 0b0000'0000'0000'1000;
  static constexpr uint16_t kHandleValueMask = 0b1111'1111'1111'0000;
 
  enum class Type : uint8_t {
    Undefined,
    Point,
    Percent,
    Number,
    Auto,
    Keyword
  };
 
  // Intentionally leaving out auto as a fast path
  enum class Keyword : uint8_t { MaxContent, FitContent, Stretch };
 
  constexpr bool isKeyword(Keyword keyword) const {
    return type() == Type::Keyword && value() == static_cast<uint16_t>(keyword);
  }
 
  constexpr Type type() const {
    return static_cast<Type>(repr_ & kHandleTypeMask);
  }
 
  constexpr void setType(Type handleType) {
    repr_ &= (~kHandleTypeMask);
    repr_ |= static_cast<uint8_t>(handleType);
  }
 
  constexpr uint16_t value() const {
    return repr_ >> 4;
  }
 
  constexpr void setValue(uint16_t value) {
    repr_ &= (~kHandleValueMask);
    repr_ |= (value << 4);
  }
 
  constexpr bool isValueIndexed() const {
    return (repr_ & kHandleIndexedMask) != 0;
  }
 
  constexpr void setValueIsIndexed() {
    repr_ |= kHandleIndexedMask;
  }
 
  uint16_t repr_{0};
};
 
#pragma pack(pop)
 
} // namespace facebook::yoga