getFilename.swift

func getFilename(_ string: StaticString) -> String {
    guard string.hasPointerRepresentation else {
        return String(string.unicodeScalar)
    }

    var index = string.utf8CodeUnitCount
    while index > 1 {
        index -= 1
        let pointer = string.utf8Start + index
        if UnicodeScalar(pointer.predecessor().pointee) == "/" {
            return String(cString: pointer)
        }
    }
    return String(cString: string.utf8Start)
}

print(filename("foo/bar/hoge.swift"))
print(filename("hoge.swift"))
print(filename("hoge.swift////"))
print(filename(""))
print(filename("/"))
print(filename("///"))
print(filename("あいう/えお/😆😆😆.swift"))