Instance Method replaceSubrange(_:with:count:) iOS 8.0+ iPadOS 8.0+ Mac Catalyst 8.0+ macOS 10.10+ tvOS 9.0+ watchOS 2.0+ Replaces a region of bytes in the data with bytes from memory. mutating func replaceSubrange(_ subrange: Range<Data.Index>, with bytes: UnsafeRawPointer, count cnt: Int)