This method is equivalent to the UnmanagedMemoryStream.#ctor(Byte*, long, long, FileAccess) constructor. It supports methods that need to initialize the pointer before setting stream variables and, therefore, cannot call the parameterized constructor. Such methods should use the default constructor, UnmanagedMemoryStream.#ctor, initialize the pointer, and then invoke the UnmanagedMemoryStream.Initialize(Byte*, long, long, FileAccess) method.