OptionalUint.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.8;

/// @dev
/// An `OptionalUint` is either absent (the default, uninitialized value) or a
/// `uint256` from `0` through `type(uint256).max - 1`, inclusive. Note that an
/// `OptionalUint` cannot represent the max value of a `uint256`.
type OptionalUint is uint256;

/// @dev
/// Operations on `OptionalUint` values.
///
/// This library uses the terms `encode` and decode rather than the more
/// standard `wrap` and `unwrap` to avoid confusion with the built-in methods
/// on the `OptionalUint` user-defined value type.
library OptionalUints {
    OptionalUint internal constant NONE = OptionalUint.wrap(0);

    /// @dev Tests whether the given `OptionalUint` is present. If it is, call
    /// `decode` to get its value.
    function isPresent(OptionalUint ox) internal pure returns (bool) {
        return OptionalUint.unwrap(ox) != 0;
    }

    /// @dev Encodes a `uint256` as an `OptionalUint` that is present with the
    /// given value, which must be at most `type(uint256).max - 1`. It always
    /// holds that `OptionalUints.encode(x).decode() == x`.
    function encode(uint256 x) internal pure returns (OptionalUint) {
        return OptionalUint.wrap(x + 1);
    }

    /// @dev Decodes a `uint256` that is known to be present. If `ox` is not
    /// actually present, execution reverts. See `isPresent`.
    function decode(OptionalUint ox) internal pure returns (uint256 x) {
        return OptionalUint.unwrap(ox) - 1;
    }
}