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IO[DONT]WAIT
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Initiates completion operations for a nowait I/O request.

Syntax

fnum := IO[DONT]WAIT ([filenum][,target][,tcount][,cstation])

Parameters

fnum (returned function value)

16-bit integer. The socket/VC socket descriptor for which an I/O request has completed. Zero indicates no completion. If there are any nowait file access requests outstanding, and if the filenum parameter is zero, the returned function value may be an actual file number.

filenum (input)

16-bit integer, by value. The call/VC socket descriptor indicating the socket or connection (that is, call or VC socket) for which the nowait I/O request was issued. If omitted, or if the value is zero, any nowait NetIPC or file request issued by the calling process may be completed by this intrinsic call.

target

Array of 16-bit values, by reference. Not used by NetIPC.

tcount (output)

16-bit integer, by reference. Returns the amount of data received after a nowait IPCRECV call. The actual data will be in the IPCRECV data parameter.

station (output)

16-bit integer (unsigned), by reference. Bit one is returned on if the completed request was a send, off if it was a receive. All other bits will be off.

Description

Either IOWAIT or IODONTWAIT is needed to complete a NetIPC nowait send or receive request. IOWAIT waits until a request can be completed; IODONTWAIT checks to see if a request can be completed and then immediately returns control to the calling process.

If a nowait IPCSEND, IPCRECVCN, or IPCRECV request is issued, the data and flags parameters (if specified) must exist when IOWAIT or IODONTWAIT is called. In other words, these parameters must be global to both the IPC intrinsic that initiates the request and the IO[DONT]WAIT that attempts to complete the I/O.

All parameters are optional (option variable). In general, the condition codes returned by IOWAIT/IODONTWAIT for socket I/O have the following meanings:

  • CCE — Succeeded.

  • CCL — Failed.

  • CCG — The operation succeeded but a noncritical error occurred (for example, the flags parameter was out of bounds).

IOWAIT and IODONTWAIT can be called in split stack mode.



Asynchronous I/O
  		 


Chapter 4 NetIPC Examples  
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