Solidity Decimal String Helpers

DecimalStrings.sol

function decimalString(uint256 number, uint8 decimals, bool isPercent) private pure returns(string memory){
    uint8 percentBufferOffset = isPercent ? 1 : 0;
    uint256 tenPowDecimals = 10 ** decimals;

    uint256 temp = number;
    uint8 digits;
    uint8 numSigfigs;
    while (temp != 0) {
        if (numSigfigs > 0) {
            // count all digits preceding least significant figure
            numSigfigs++;
        } else if (temp % 10 != 0) {
            numSigfigs++;
        }
        digits++;
        temp /= 10;
    }

    DecimalStringParams memory params;
    params.isPercent = isPercent;
    if((digits - numSigfigs) >= decimals) {
        // no decimals, ensure we preserve all trailing zeros
        params.sigfigs = number / tenPowDecimals;
        params.sigfigIndex = digits - decimals;
        params.bufferLength = params.sigfigIndex + percentBufferOffset;
    } else {
        // chop all trailing zeros for numbers with decimals
        params.sigfigs = number / (10 ** (digits - numSigfigs));
        if(tenPowDecimals > number){
            // number is less tahn one
            // in this case, there may be leading zeros after the decimal place 
            // that need to be added

            // offset leading zeros by two to account for leading '0.'
            params.zerosStartIndex = 2;
            params.zerosEndIndex = decimals - digits + 2;
            params.sigfigIndex = numSigfigs + params.zerosEndIndex;
            params.bufferLength = params.sigfigIndex + percentBufferOffset;
            params.isLessThanOne = true;
        } else {
            // In this case, there are digits before and
            // after the decimal place
            params.sigfigIndex = numSigfigs + 1;
            params.decimalIndex = digits - decimals + 1;
        }
    }
    params.bufferLength = params.sigfigIndex + percentBufferOffset;
    return generateDecimalString(params);
}

// With modifications, the below taken 
// from https://github.com/Uniswap/uniswap-v3-periphery/blob/main/contracts/libraries/NFTDescriptor.sol#L189-L231

struct DecimalStringParams {
    // significant figures of decimal
    uint256 sigfigs;
    // length of decimal string
    uint8 bufferLength;
    // ending index for significant figures (funtion works backwards when copying sigfigs)
    uint8 sigfigIndex;
    // index of decimal place (0 if no decimal)
    uint8 decimalIndex;
    // start index for trailing/leading 0's for very small/large numbers
    uint8 zerosStartIndex;
    // end index for trailing/leading 0's for very small/large numbers
    uint8 zerosEndIndex;
    // true if decimal number is less than one
    bool isLessThanOne;
    // true if string should include "%"
    bool isPercent;
}

function generateDecimalString(DecimalStringParams memory params) private pure returns (string memory) {
    bytes memory buffer = new bytes(params.bufferLength);
    if (params.isPercent) {
        buffer[buffer.length - 1] = '%';
    }
    if (params.isLessThanOne) {
        buffer[0] = '0';
        buffer[1] = '.';
    }

    // add leading/trailing 0's
    for (uint256 zerosCursor = params.zerosStartIndex; zerosCursor < params.zerosEndIndex; zerosCursor++) {
        buffer[zerosCursor] = bytes1(uint8(48));
    }
    // add sigfigs
    while (params.sigfigs > 0) {
        if (params.decimalIndex > 0 && params.sigfigIndex == params.decimalIndex) {
            buffer[--params.sigfigIndex] = '.';
        }
        buffer[--params.sigfigIndex] = bytes1(uint8(uint256(48) + (params.sigfigs % 10)));
        params.sigfigs /= 10;
    }
    return string(buffer);
}