func withUnsafeMutableBytes(of:_:)(of value: inout T, _ body: (UnsafeMutableRawBufferPointer) throws -> Result) rethrows -> Result Invokes the given closure with a mutable buffer pointer covering the raw bytes of the given argument. The buffer pointer argument to the body closure provides a collection interface to the raw bytes of value. The buffer is the size of the instance passed as value and does not include any remote storage.