Swift wrapper around GNU readline

Readline.swift

// #include <readline/readline.h>

extension String {
    private init(pointer: UnsafePointer<Int8>) {
        self.init()
        var p = pointer
        while p.memory != 0 {
            append(Character(UnicodeScalar(unsafeBitCast(p.memory, UInt8.self))))
            p = p.successor()
        }
    }
}

func readLine(prompt: String = "", addHistory: Bool = false) -> String? {
    let line = readline(prompt)
    guard line != nil else { return nil }
    defer { free(line) }
    if addHistory { add_history(line) }
    return String(pointer: line)
}

while let line = readLine("> ", addHistory: true) {
    print(line)
}