Copies a number of bytes from the start of the receiver's data into a given buffer.
- iOS 8.0+
- macOS 10.10+
- tvOS 9.0+
- watchOS 2.0+
A buffer into which to copy data.
The number of bytes from the start of the receiver's data to copy to
The number of bytes copied is the smaller of the
length parameter and the
length of the data encapsulated in the object.