CharacterSet+Hack.swift

private func split(_ str: String, _ length: Int) -> [String] {
    // based on http://stackoverflow.com/a/38980231/1777634
    return stride(from: 0, to: str.characters.count, by: length).map { idx -> String in
        let startIndex = str.index(str.startIndex, offsetBy: idx)
        let endIndex = str.index(startIndex, offsetBy: length,
                                 limitedBy: str.endIndex) ?? str.endIndex
        return str[startIndex..<endIndex]
    }
}

extension CharacterSet {
    init(fixedCharactersIn string: String) {
        #if os(Linux)
            // workaround for https://bugs.swift.org/browse/SR-3215 and
            // https://bugs.swift.org/browse/SR-3282
            let sets = split(string, 63).map { CharacterSet(charactersIn: $0) }
            let finalSet = sets.reduce(CharacterSet()) { (acc, set) -> CharacterSet in
                acc.union(set)
            }

            self = finalSet
        #else
            self.init(charactersIn: string)
        #endif
    }
}