Copyright ©1995 by NeXT Computer, Inc.  All Rights Reserved.


Inherits From: Object
Conforms To: NXTransport (Distributed Objects)
Declared In: machkit/NXData.h

Class Description

NXData is an object-oriented wrapper for data.  It's especially useful in Distributed Objects applications because of its conformance to the NXTransport protocol, allowing NXData objects to be copied or moved between applications.  NXData can be used to wrap data of any size; it allocates small amounts of memory from its own zone using a malloc-related function, and allocates page-aligned data from the virtual memory system for requests of a page or larger.  NXData can also be used to wrap preexisting data, regardless of how the data was allocated.

If data is to be moved between applications (rather than copied), you may find it necessary to override the encodeRemotelyFor:... method in a subclass of NXData to ensure that data is properly deallocated after it is passed across a connection; see the Distributed Objects introduction for more information on moving objects between applications.

Instance Variables

None declared in this class.

Adopted Protocols

NXTransport encodeRemotelyFor:freeAfterEncoding:isBycopy:

Method Types

Initializing and freeing instances
Getting the object's data data
Getting the data's size size
Copying the object copyFromZone:

Instance Methods

copyFromZone:(NXZone *)zone

Returns a newly allocated NXData instance containing a copy of the receiver's data.  The new object's data will be deallocated when the new object gets freed.

(void *)data

Returns a pointer to the data contained in the object.

encodeRemotelyFor: freeAfterEncoding:isBycopy:
encodeRemotelyFor: (NXConnection *)conn
freeAfterEncoding:(BOOL *)flagPointer

Returns self to indicate that a copy of the NXData object (and not a proxy to it) is to be copied across a connection any time the object is vended to a remote object.  The data for the remote copy will be freed when the copy is freed.  If you want the local NXData to be freed after being sent across the connection, you will need to override this method to set the boolean indicated by flagPointer to YES.


Deallocates the receiver's storage, including the data if it was initialized to do so, and returns nil.

See also:  initWithData:size:dealloc:, initWithSize:

initWithData:(void *)data
size:(unsigned int)size

Initializes the receiver, a new NXData object, with data, which must be at most size bytes long.  If flag is YES, then data will be deallocated when the NXData object is freed.  data could have been allocated with vm_allocate() or a malloc() variant. Returns self.

See also:  initWithSize:, free

initWithSize:(unsigned int)size

Initializes the receiver, a new NXData object, so that it can contain at most size bytes of data.  The memory will be allocated directly from the virtual memory system if it is one page or greater in size (though applications shouldn't care where the memory came from); otherwise the data will be allocated from the object's zone.  The data will be freed when the NXData object is freed.  Returns self.

See also:  initWithData:size:dealloc:, free

(unsigned int)size

Returns the size of the data that the object holds.