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HP OpenVMS Systemsask the wizard |
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The Question is: I am writing a communications process that has to drive a UCX TN3270 terminal session in a subprocess. It has to capture the output and use the info to drive an automated process. I have found the Pseudo Terminal driver, FTAx: device using the calls PT D$create, read and write. The control process is written in DEC Basic. The PTD$ routines require that the IO buffers be page aligned and be in contiguous pages, etc. I create the pages using the sys$expreg call and use the return address in the ptd$create and that returns ok. How do I get my IO buffers in Basic to point to this newly created space? Using MAP, Declare and/or Record statements in Basic? See the OpenVMS I/O User's Reference Manual, Appendix C. I am stumped and/or my brain's memory block is swapped out and can't get beyond this. Or, alternatively, are there other Pseudo Terminal-like devices I could use for the control function for the subprocess? Mailboxes won't work because the TN3270 driver has to see a VT-like device. Thanks in advance. Charlie The Answer is : BASIC typically uses its own internal I/O buffer pool. If you wish to manage your own buffer pool, you will want to use operations that support the specification of your own buffers, and a programming language that makes use of pointers acceptably possible for your needs. (BASIC does have the ability to work "by reference", but this can cause you some problems.) If you can recode the BASIC record buffers -- as differentiated from the internal I/O buffers -- to use a separate program section, you may well be able to achieve what you want by overmapping the BASIC record buffer section with your own buffer pool using the LINKER. Also using the LINKER, you can specify page alignment -- pages on Alpha can be up to 64 kilobytes in size -- for the buffers based on the program section. (Though the Wizard is not at all certain that directly connecting the BASIC record structures to the pseudo-terminal transfers makes any sense -- the Wizard would tend to assume that the two record structures would differ and would thus require some sort of translation or the relocation of field(s) in the BASIC buffer into the field(s) in the pseudo-terminal buffer.) The Wizard would strongly recommend moving to a non-terminal based protocol for communications with the remote system -- the TN3270 terminal interface is intended for user use, and not particularly for programmatic control. You obviously have IP available, can you use a peer-to-peer or client-server IP protocol -- your own, or RPC or similar -- to control the remote communications?
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