Number: 1338

Date:  5-Jun-84 11':48':41

Submitter: JonL.pa

Source: JonL.pa

Subject: document SWAPPEDXPOINTER FULLXPOINTER in impl manual

Assigned To: 

Attn: Masinter,JonL

Status: Open

In/By: 

Problem Type: Documentation

Impact: Annoying

Difficulty: Easy

Frequency: Intermittent

Priority: Hopefully

System: Programming Environment

Subsystem: Record Package

Machine: 1132

Disk: 

Lisp Version: 31-May-84 22':31':16

Source Files: 

Microcode Version: 5124

Memory Size: 4096

File Server: 

Server Software Version: 

Disposition: [Masinter -- this originally was AR to IMPLEMENT SWAPPEDXPOINTER. I changed it to be an ar to Document them.]'
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["JonL.pa" "25-Sep-84 02':02':51" Assigned% To': Attn': Description':]

Description: A swapped POINTER (or XPOINTER) field is needed for Mesa communications, espeically w.r.t. the CSB pointer in the IOPage for RS232.  Apparently others have requested a swapped pointer field in the past (Bill did some months before the AR system).  Some of these Mesa communications pointers ** do not ** lie on an even word boundary, so no check should automatically be supplied.'
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Date':  4 Jun 84 17':11 PDT'
From': JonL.pa'
Subject': swapped (X)POINTER fields'
To': vanMelle,Stansbury'
cc': LispCore^'
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I''ve just submitted an AR on the need for such a field type in the RECORD package.  I''m prodded by the need for a couple of communication cells to the IOP, which use the Mesa pointer format, but I''ve heard that there are other sources for this need. (Indeed, isn''t SWAPPEDFIXP a standard option now?).'
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Any comments?'
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-- JonL --'
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P.S. A "swapped mumble" field is one in which the sense of hiword/loword is the reverse of what it is in InterLisp-D.  In Interlisp, the "hiword" (the segment number part of the adress) is stored in the lower-address word of the two words needed; in Mesa, the "hiword" is stored in the higher-address word.'
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[This hasn''t worked right until quite recently -- although the type SWAPPEDXPOINTER has been admissible for some time, it had been requiring double-word alignment.  -- JonL -- 25-Sep-84]'


Workaround: 

Test Case: 

Edit-By: JonL.pa

Edit-Date: 25-Sep-84 02':02':54