dispatch_data_t
An immutable object representing a contiguous or sparse region of memory.
Declaration
typealias dispatch_data_t = __DispatchDataDiscussion
Any direct access to the memory in a dispatch data object must not modify that memory.
In 64-bit apps, you may cast a dispatch_data_t type to an NSData object. However, you may not perform a reverse cast — that is, cast an NSData object to a dispatch_data_t type.