Type ASSEMBLE
Source Lines : 926
Fixes Applied : 3
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [HRC015DS]
Module
DMSERS (ERASE)
Function
TO DELETE A FILE OR RELATED GROUP OF FILES FROM
READ-WRITE DISK(S).
Attributes
NUCLEUS RESIDENT
Operation
DMSERS CHECKS THE PARAMETER LIST FOR ERRORS BY THE
CALLER. THE FILENAME
AND FILETYPE MUST EACH BE GIVEN, OR ELSE A ASTERISK
IN PLACE OF FILENAME OR FILETYPE TO INDICATE ALL
NAMES AND/OR ALL TYPES. THE FILEMODE MAY BE OMITTED
IN WHICH CASE THE FIRST READ-WRITE DISK IS ASSUMED.
IF NOT OMITTED, THE FILEMODE MUST BE ALPHABETIC. IF
ALPHABETIC, A MODE NUMBER IS ACCEPTABLE.
FOR EXAMPLE, A CALL OF ERASE * TEXT A5 WOULD ERASE
ALL TEXT FILES ON THE A-DISK THAT HAD A MODE NUMBER
OF 5. ALL OTHER TEXT FILES ON ANY DISKS WOULD REMAIN
INTACT, AND ALL OTHER A5 FILES WOULD REMAIN ALSO.
IF ANY ERRORS ARE DETECTED IN THE PARAMETER LIST,
ERROR 1 IS RETURNED, AND NOTHING IS ERASED.
AFTER CHECKING THE PARAMETER LIST AND SETTING
FLAGBITS AS NEEDED, DMSERS CHECKS FOR A
GIVEN FILE AND DELETES IT, IF FOUND, USING THE
FOLLOWING PROCEDURE:
1. DMSLAF IS CALLED TO DETERMINE IF THE FILE
TO BE ERASED IS STILL ACTIVE - THAT IS, IN THE
ACTIVE FILE TABLE (AFT). IF IT IS (ONLY A FILE ON
A READ-WRITE DISK IS ACCEPTABLE, OF COURSE), THEN
IT IS TEMPORARILY CLOSED VIA A CALL TO EFINIS IN
THE DMSFNT ROUTINE, WHICH PERFORMS JUST ENOUGH OF
THE NORMAL CLOSING STEPS ORDINARILY PERFORMED BY
DMSFNS TO PERMIT THE FILE TO BE SUCCESSFULLY
ERASED. PROCEEDS
THEN TO STEP 3 BELOW.
2. IF NOT FOUND BY DMSLAF, THEN DMSERS CALLS DMSLFS
TO FIND THE FILE. IF NOT FOUND, EXIT IS MADE FROM
DMSERS AS DESCRIBED IN STEP 14 BELOW.
3. WHEN THE FILE HAS BEEN FOUND EITHER BY DMSLAF (AND
DMSFNSE CALLED), OR BY DMSLFSW, THEN DMSFNST IS
CALLED TO TEMPORARILY CLOSE ALL OUTPUT FILES FOR
THIS
PARTICULAR DISK (UNLESS THIS WAS ALREADY
ACCOMPLISHED BY AN EARLIER EXCURSION THROUGH THIS
PROCEDURE FOR ANOTHER FILE ON THE SAME DISK).
4. DMSERS THEN CHECKS THE TYPE OPTION FLAG BIT TO
DETERMINE IF THE USER SPECIFIED
THAT THE IDENTIFIER(S) OF THE FILE(S) BEING ERASED
ARE TO BE TYPED TO THE CONSOLE.
IF THE BIT IS ON, THE PLIST IS SET UP, AND A CALL
IS MADE TO DMSCWR.
5. BEFORE RELEASING ANY TRACKS BELONGING TO THE FILE
THAT HAS BEEN FOUND, DMSERS CALLS A SPECIAL ENTRY
IN THE DMSAUD ROUTINE TO RESERVE ENOUGH DISK
RECORDS FOR A NEW FILE DIRECTORY TO BE UPDATED
WHEN THE FILE HAS BEEN ERASED. THIS PROCEDURE IS
PART OF CMS'S DOUBLE DIRECTORY SCHEME, AND ENSURES
THAT THE FILE DIRECTORY FOR THE DISK FROM WHICH
THE FILE IS BEING ERASED IS UPDATED WHEN AND ONLY
WHEN THE ERASE HAS BEEN COMPLETED. (IF ANY SYSTEM
MALFUNCTION OR USER INTERVENTION INTERRUPTS THE
PROCESS BEFORE COMPLETION, THE OLD FILE DIRECTORY
AND THE FILE BEING ERASED ARE BOTH STILL INTACT.)
6. THEN (UNLESS IT IS ALREADY AVAILABLE), 1000 BYTES
OF FREE STORAGE ARE OBTAINED VIA
DMSFREE, FOR USE IN READING IN THE FIRST AND OTHER
(IF ANY) CHAIN LINKS OF THE FILE.
7. NEXT THE FIRST CHAIN LINK OF THE FILE IS READ INTO
CORE, INTO THE FIRST 200 BYTES OF
FREE STORAGE AREA, VIA DMSDIOR.
8. THE DATA BLOCKS POINTED TO BY THE FIRST CHAIN LINK
ARE THEN RELEASED VIA DMSTRKX, AND THE FIRST CHAIN
LINK ITSELF VIA DMSTQQX (THE FIRST CHAIN LINK
REMAINING IN CORE, HOWEVER).
9. IF ANY DATA BLOCKS REMAIN, ACCORDING TO THE FSTDBC
DATA-BLOCK-COUNT IN THE FST ENTRY, THEN ADDITIONAL
CHAIN LINKS ARE READ INTO CORE, AS POINTED TO BY
THE FIRST CHAIN LINK. FOR EACH OF THESE NTH CHAIN
LINKS, THE DATA BLOCKS POINTED TO THEREBY ARE
RELEASED VIA DMSTRKX, AND THEN THE CHAIN LINK
ITSELF. THIS PROCESS CONTINUES, WITH
A COUNT OF DATA BLOCKS RETURNED BEING DECREMENTED,
UNTIL THERE ARE NONE LEFT, OR ALL AVAILABLE CHAIN
LINKS HAVE BEEN EXHAUSTED.
10. AT THIS POINT, ALL DATA BLOCKS AND CHAIN LINKS
HAVE BEEN GIVEN BACK TO THE QMSK AND
QQMSK VIA APPROPRIATE CALLS TO DMSTRKX AND THE ONE
CALL TO DMSTQQX. NOW A CHECK IS MADE
TO SEE IF PERCHANCE THE FILE BEING ERASED HAPPENS
TO BE CONTAINED IN STATEFST. IF SO,
THE CONTENTS OF STATEFST ARE CLEARED TO REFLECT HRC015DS
THE DELETION OF THE GIVEN FILE. (NOTE - DMSBRD
UTILIZES THE STATEFST INFORMATION IN SOME
CIRCUMSTANCES; THUS IT MUST BE EITHER CORRECT OR
NULL.)
11. NEXT PROVISIONS ARE MADE TO KEEP THE FST
HYPERBLOCKS COMPACTED, FOR THE DISK ON WHICH THE
FILE WAS FOUND AND ERASED. IN THIS PROCESS, THE
LAST FST ENTRY FOR THE DISK INVOLVED IS MOVED TO
WHERE THE FST ENTRY WAS FOR THE FILE THAT WE JUST
ERASED, AND THE
PLACE FROM WHICH IT WAS MOVED IS CLEARED. A CHECK
IS MADE OF THE ACTIVE FILE TABLE VIA DMSLAFNX
IN CASE AN ACTIVE FILE ENTRY POINTS TO THE FILE
MOVED, IN WHICH CASE THE POINTER IS CORRECTED; THE
POINTER FOLLOWING STATEFST IS ALSO CHECKED, AND
CORRECTED IF NECESSARY. IN ANY EVENT, THE
COMPACTING IS CAREFULLY ACCOMPLISHED, WITH ALL
POINTERS, DISPLACEMENTS, BLOCK COUNTS, ETC., BEING
CORRECTED AS NECESSARY.
12. FINALLY, A CALL TO THE OTHER ENTRY OF DMSAUD
IS MADE TO COMPLETE THE UPDATING OF
THE FILE DIRECTORY FOR THE DISK INVOLVED.
13. AT THIS POINT, IF THE ENTIRE FST HYPERBLOCK AND
THE LAST FST ENTRY IN THE PRECEDING HYPERBLOCK
HAVE ALL BECOME CLEAR, THE LAST HYPERBLOCK IS
RETURNED TO FREE STORAGE, AND ALL POINTERS AND
COUNTS CORRECTED ACCORDINGLY. (THIS IS DONE TO
AVOID KEEPING A NUMBER OF EMPTY HYPERBLOCKS IN
CORE IN CASE A LARGE NUMBER OF FILES ARE ERASED.)
14. FINALLY, THE ENTIRE PROCEDURE IS REPEATED STARTING
AT STEP 1, IF THE PARAMETER LIST SPECIFIED ALL
NAMES, TYPES, OR MODES.
15. WHEN ALL APPROPRIATE ERASING (IF ANY) HAS BEEN
COMPLETED, DMSERS RETURNS THE 1000-BYTE
BUFFER TO FREE STORAGE, AND EXISTS TO THE CALLER
WITH THE APPROPRIATE ERROR CODE.
IF NO FILES AT ALL WERE ERASED, DMSERS RETURNS AN
ERROR CODE 2, BUT WITHOUT AN ERROR MESSAGE. (SEVERAL
SYSTEM PROGRAMS CALL DMSERS TO ELIMINATE OLD
LISTINGS, OLD TEXT FILES, ETC., IN CASE THEY MIGHT
EXIST, SO THAT AN ERROR MESSAGE FOR FILE NOT FOUND IN
DMSERS ITSELF WOULD BE IMPRACTICAL.)
SEVERAL ERROR CONDITIONS ARE DETECTED BY DMSERS. ON
ONE OF THESE, A PERMANENT I/O ERROR IN READING IN A
CHAIN LINK DUE TO HARDWARE DISK ERRORS, DMSERS
PURPOSELY INVOKES
THE CODE AT DMSFNSD (WITHIN THE FINIS COMMAND) TO
LEAVE THE FILE DIRECTORY INTACT UNTIL
THE DISK ERROR CAN BE CORRECTED.
ON ALL OTHERS, WHEN THE ERROR IS DETECTED, DMSERS
CEASES TO GIVE BACK RECORDS USING
DMSTKX AND/OR DMSTQQX, BUT DELETES THE FILES AND
COMPACTS THE DIRECTORY AS USUAL. AN ERROR 3 IS GIVEN
ON EXIT, WHEN DMSERS IS FINISHED.
THIS FEATURE MAKES IT FEASIBLE TO ERASE A FAULTY FILE
FROM ONE'S DIRECTORY WITHOUT ENDANGERING THE
INTEGRITY OF OTHER FILES ON THE SAME DISK.
Calls to Other Routines
DMSLAD - LOCATE THE FIRST R/W DISK
DMSLAF - FIND THE ACTIVE FILE TABLE FOR THE GIVEN FILE
DMSLAFFE -FIND THE NEXT ACTIVE FILE TABLE
DMSFNSD - 'DIE' IF PERMANENT ERROR READING DISK
DMSFNST - TEMPORARILY CLOSE A FILE
DMSFREE - GET FREE STORAGE
DMSFRET - RETURN FREE STORAGE
DMSLFS - FIND THE SPECIFIED FILE STATUS TABLE
DMSTQQ - ALLOCATE A 200 BYTE DISK AREA
DMSDIOR -
DMSTRKW -
DMSAUD - CLOSE ALL FILES AND UPDATE THE USER FILE DIRECTORY
DMSCWRB - TYPE A LINE TO THE TERMINAL
DMSTQQX -