function `toString` as an example of how `while` loops are used in Solidity

HexString.sol

// SPDX-License-Identifier: GPL-2.0-or-later

pragma solidity ^0.7.6;

/// @title HexStrings
/// Based on https://github.com/OpenZeppelin/openzeppelin-contracts/blob/8dd744fc1843d285c38e54e9d439dea7f6b93495/contracts/utils/Strings.sol
library HexStrings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /// @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
    function toString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /// @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        
        // function body (omitted for brievity)
        
    }
}