openzeppelin-contracts/contracts/drafts/Strings.sol

pragma solidity ^0.5.0;

/**
 * @title Strings
 * @dev String operations.
 */
library Strings {
    /**
     * Concatenates two strings.
     * string(abi.encodePacked(a, b))
     * https://solidity.readthedocs.io/en/latest/types.html?highlight=concatenate
     */

    /**
     * @dev Converts a uint256 to a string.
     * via OraclizeAPI - MIT licence
     * https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol
     */
    function fromUint256(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        uint256 index = digits - 1;
        temp = value;
        while (temp != 0) {
            buffer[index--] = byte(uint8(48 + temp % 10));
            temp /= 10;
        }
        return string(buffer);
    }
}