Type Definitions

XObj

An XObj is the fundamental identifier in the system. It can represent either a protocol or a session. Fields which can be read or written by the programmer are so indicated.

If you think of the x-kernel as implementing protocol and session graphs, then each XObj represents a node in one of the graphs. Furthermore, an object's down vector represents graph edges; they contain pointers to the XObjs that are below the object in the protocol or session graphs. The fields myprotl and up link a session to the protocols that own and created the session, respectively.

Enable Objects

The Enable object is provided for use by the programmer in maintaining maps that associate identifiers and protocols or sessions. A pointer to an Enable object is often used as the internal identifier in mapBind calls. An Enable object has a field for reference counting. Protocol writers will find this useful in handling xOpenEnable calls with identical participants-the calls are redundant with respect to session creation-but they must be reference counted in order to properly handle xOpenDisable calls.

Return Values

Most routines have a return value type of xkern_return_t, which is either XK_SUCCESS or XK_FAILURE. Routines that return type XObj have a failure value of ERR_XOBJ. Some message handling routines use type xmsg_handle; see section 2.2.6. Severe error conditions will result in console error messages and the termination of the x-kernel.

Function Types

The following typedefs are used in the XObj structure and throughout this document:

typedef xkern_return_t ( * Pfk )();
typedef void ( * Pfv )();
typedef struct xobj * ( * Pfo )();
typedef xmsg_handle_t ( * Pfh )();
typedef int ( * Pfi )();