swift int 与UInt8相互转化

// 将int转化为UInt8
@objc class func toUint(signed: Int) -> UInt {

    let unsigned = signed >= 0 ?
        UInt(signed) :
        UInt(signed  - Int.min) + UInt(Int.max) + 1

    return unsigned
}

// 将UInt8 转化为 int
func convertToInt(unsigned: UInt) -> Int {
let signed = (unsigned <= UInt(Int.max)) ?
Int(unsigned) :
Int(unsigned - UInt(Int.max) - 1) + Int.min

    return signed
}