问SWIFT中的指针、指针算法和原始数据？

class RawData {
    var data: NSData!

    init(rawData: NSData) {
      data = rawData
    }

    func read<T>(byteLocation: Int) -> T {
      let bytes = data.subdataWithRange(NSMakeRange(byteLocation, sizeof(T))).bytes
      return UnsafePointer<T>(bytes).memory
    }

    func example_ReadAnIntAtByteLocation5() -> Int {
      return read(5) as Int
    }
}

@implementation RawDataOffsetPointer

inline void* offsetPointer(void* ptr, int bytes){
    return (char*)ptr + bytes;
}

@end

func read<T>(byteLocation: Int) -> T {
  let ptr = offsetPointer(data.bytes, CInt(byteLocation))
  return UnsafePointer<T>(ptr).memory
}