[Swift]text coloring by escape code

colorTest.swift

#!/usr/bin/swift
import Foundation

public enum ESCCode : UInt {
    case Reset = 0, Bold = 1, Faint, UnderLine = 4, BlinkSlow, Negative = 7
    case Black = 30, Red, Green, Yellow, Blue, Magenda, Cyan, White
    case BackgroundBlack = 40, BackgroundRed, BackgroundGreen, BackgroundYellow, BackgroundBlue, BackgroundMagenda, BackgroundCyan, BackgroundWhite
    
    static let backGroundColorOffset: UInt = 10
    static func escapeCode(value: UInt) -> String { return "\u{1b}[\(value)m" }
    
    var escString: String { return self.dynamicType.escapeCode(self.rawValue) }
}
extension String {
    func escape(esc: ESCCode, reset: Bool = true) -> String {
        return "\(esc.escString)\(self)\(reset ? ESCCode.Reset.escString : "")"
    }
}

public func printError(message: String, exit shouldTerminate: Bool = false, terminator: String = "\n") {
    if let data = "\(message.escape(.Red))\(terminator)".dataUsingEncoding(NSUTF8StringEncoding) {
        NSFileHandle.fileHandleWithStandardError().writeData(data)
    }
    if shouldTerminate { exit(1) }
}

let str: String = "abcABC"
for i: UInt in ESCCode.Bold.rawValue..<ESCCode.Negative.rawValue+1 {
    if let esc = ESCCode(rawValue: i) {
        print("\\x1b[\(esc.rawValue)m  \(str.escape(esc))")
    }
}
print("")

print("    | \\x1b[3*m | \\x1b[4*m |")
print("___ | ________ | ________ |")
for i: UInt in ESCCode.Black.rawValue ..< ESCCode.White.rawValue+1 {
    if let color = ESCCode(rawValue: i), bcolor = ESCCode(rawValue: i+ESCCode.backGroundColorOffset) {
        print("*=\(i-ESCCode.Black.rawValue) |  \(str.escape(color))  |  \(str.escape(bcolor))  | ");
    }
}

print("")

printError("警告")
printError("warning", exit: true)
print("unreachable")