Entry Specifications

XCF passes information to the server exit user routine in a parameter list and in registers.

Version 0 of the server exit parameter list (SXPL). ixcysrvr_tSXPL of the IXCYSXPL mapping macro maps the parameter list that is passed to a server exit routine.

The Server Exit Parameter List (SXPL) is passed to the server exit routine by XCF. The SXPL resides in the primary address space of the server, and is defined in the IXCYSRVR macro by the mapping ixcysrvr_tSXPL. Within the SXPL, the field SXPL_ServerCode defines what function the server exit is to perform. The content of the SXPL varies according to function. The "base" portion of the SXPL is common to all functions. The content of the "function specific" portion of the SXPL is unique to the particular function. Thus, the SXPL_ServerCode determines not only what function the server exit is to perform, but also how to map the SXPL.

The field SXPL_ParameterOffset within the base portion of the SXPL indicates the offset (relative to the address of the SXPL) where the function specific parameters were stored by XCF. SXPL_ServerCode will have one of the following constant values defined in the IXCYSRVR macro:

IXCYSRVR_KSC_INITSERVER: The server exit is to perform whatever initialization is appropriate. The function specific parameters mapped by ixcysrvr_tInitServer contain copies of the keyword values that were specified on the IXCSRVR REQTYPE=START invocation that started the server. The first call of the server exit routine is always for the initialize function. XCF makes this call once.
IXCYSRVR_KSC_GETWORKAREA: The server exit is to obtain a work area for XCF to use. The function-specific parameters mapped by ixcysrvr_tGetWorkArea indicate the amount of storage that XCF requires. The server exit routine is expected to obtain the requested storage, update the SXPL_WAD field to indicate the location and size of the storage provided, and return to XCF. Note that on entry to the server exit, the SXPL_WAD field describes the work area that was last given to XCF. If there is an existing work area, the server exit will likely need to dispose of that storage before updating the SXPL_WAD with information about a new work area. If the work area provided by the server is not accessible, XCF stops the server.
IXCYSRVR_KSC_REQUEST: The server exit is to process a request. The function specific parameters mapped by ixcysrvr_tRequest contain copies of most of the keyword values specified on the IXCSEND macro invocation that was used by the client to send the request. The function specific parameters also include a "message descriptor" that identifies the size and location of the content of the request message.

Registers at Entry

When the server exit routine receives control, the GPRs contain:

Register: Contents
0: Used as a work register by the system.
1: Address of an SXPL (see ixcysrvr_tSXPL)
2-12: N/A
13: Same value as R13 when the IXCSRVR START call is invoked to define the server
14: Return address
15: Entry point address of server exit.

When the server exit routine receives control, the ARs contain:

AR0-AR1 -: Set to ALET of a primary address space (0)
AR2-R12 -: N/A
AR13: Same value as AR13 had when the IXCSRVR START call was invoked
AR14-AR15: N/A