utf8mb4

utf8mb4.swift

extension UTF8 {
    static func byteCount(_ input: UnicodeScalar) -> Int {
        var count = 0
        encode(input, into: { _ in count = count + 1 })
        return count
    }

    static func is4Bytes(_ input: UnicodeScalar) -> Bool {
        return byteCount(input) == 4
    }
}

extension String {
    var contains4BytesCharacterByUTF8Encoding: Bool {
        return unicodeScalars.contains(where: UTF8.is4Bytes)
    }
}