Type ASSEMBLE
Source Lines : 654
Fixes Applied : 1
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [HRC004DS]
Module
DMSACM (READMFD)
Function
TO READ THE MASTER FILE DIRECTORY (MFD) AND OTHER
INFORMATION INTO CORE FROM DISK.
Attributes
TRANSIENT, REENTRANT
Operation
DMSACF AND DMSACM WHEN USED TOGETHER
ARE CALLED BY DMSACC OR DMSING TO BRING ALL OR PART
OF A USER FILE DIRECTORY INTO STORAGE OR TO READ THE
LABEL OF THE O/S DISK BEING ACCESSED. DMSACM DOES
NOT BRING IN ANY FST HYPERBLOCKS (THAT BEING DONE BY
DMSACF), AND IS THEREFORE CALLED DIRECTLY BY DMSACC
WHEN ACCESSING A DISK USING THE (ERASE) OPTION.
DMSACM DOES THE FOLLOWING:
A DIAGNOSE IS ISSUED TO CP FOR THE DEVICE TYPE OF THE
ADDRESS SPECIFIED. AN ERROR CODE IS RETURNED TO THE
CALLER IF A NON-ZERO CONDITION CODE IS RETURNED FROM
DIAGNOSE(I.E. THE DEVICE IS NOT ATTACHED).
REGISTER 15 FROM DIAGNOSE IS INTERROGATED FOR THE FOLLOWING:
1) IF IT IS NOT A DASD DEVICE, AN ERROR CODE OF 3
IS RETURNED TO THE CALLER;
2) IF THE LOW ORDER BYTE OF R15 INDICATES THAT THE
DEVICE IS A HRC004DS
A 3330(X'10'), 2314(X'40'), 3340(X'01'), HRC004DS
3350(X'08') OR 3380(X'20'), HRC004DS
A X'09', X'08', X'07', X'0B', OR X'0E' HRC004DS
RESPECTIVELY, IS STORED IN THE FOURTH BYTE OF THE
12-BYTE DEVICE-TABLE ENTRY IN THE NUCON TABLE, FOR
THE PARTICULAR DEVICE GIVEN BY THE ACTIVE DISK TABLE.
IF THE DEVICE IS NONE OF THESE, CONTROL IS
RETURNED TO THE USER WITH AN ERROR CODE OF 3.
THEN THE DISK LABEL (RECORD NO. 3 - THAT IS, CYLINDER
0, HEAD 0, RECORD 3) IS READ FROM DISK AND A TEST IS
MADE TO DETERMINE IF THE DISK IS A CMS OR AN O/S DISK.
IF THE DISK IS O/S, CONTROL GOES TO A SPECIAL ROUTINE.
NEXT, THE MASTER FILE DIRECTORY (RECORD NO. 4 - THAT
IS, CYLINDER 0, HEAD 0, RECORD 4) IS READ FROM DISK
INTO A BUFFER OBTAINED FROM FREE STORAGE. (ERROR 1
IF CANNOT BE READ SUCCESSFULLY). THE FIRST HALFWORD
OF THE MFD IS CHECKED TO MAKE SURE DATA IS THERE
(ERROR 1 IF NOT).
THE DISK ADDRESSES AT THE BEGINNING OF THE MFD ARE
THEN CHECKED, SCANNING FOR AN ENDING SENTINEL OF
FFFF, FFFE, FFFD, TO DETERMINE HOW MANY FST
HYPERBLOCKS ARE ON DISK, AND WHERE THE QMSK
EXTENSIONS (IF ANY) ARE STORED ON DISK. THE NUMBER
OF FST HYPERBLOCKS IS STORED ON DISK. THE NUMBER OF
FST HYPERBLOCKS IS STORED AD ADTHBCT IN THE ACTIVE
DISK TABLE FOR FUTURE USE (USUALLY BY DMSRCF). THE
DISK COUNTS ADTNUM, ETC., ARE STORED IN THE ACTIVE
DISK TABLE FROM MFD, ALONG WITH THE NUMBER OF
CYLINDERS.
AT THIS POINT, IF THE READ-ONLY FLAG-BIT ADTFRO IN
THE ADTFLG1 FLAG IS SET, DMSACM ACCEPTS THE DISKS AS
READ-ONLY, LEAVES THE MFD BLOCK IN A FREE STORAGE
BUFFER OR JUST ENOUGHT SIZE TO INCLUDE ALL THE
DISK-ADDRESSES AT THE BEGINNING, AND EXITS TO THE
CALLER, NORMALLY DMSACF.
IF THE DISK IS NOT FLAGGED READ-ONLY, DMSACM ATTEMPTS
TO WRITE THE
MFD EXACTLY AS IS RIGHT BACK ON DISK USING DMSDIOW.
IF UNSUCCESSFUL BECAUSE THE DISK IS READ-ONLY 9(AN
ERROR 6 FROM DMSDIOW), DMSACM
FINISHES UP AS DESCRIBED IN THE ABOVE PARAGRAPH (THE
READ-ONLY BIT BEING SET NOW), AND EXIT IS
SUBSEQUENTLY MADE WITH ERROR 4 (NONFATAL).
IF THE MFD WAS SUCCESSFULLY WRITTEN BACK ON DISK, THE
READ-WRITE FLAG-BIT IS SET, AND DMSACM CONTINUES.
NEXT THE RIGHT AMOUNT OF FREE STORAGE IS OBTAINED FOR
THE QMSK BIT-MASK (DEPENDING ON THE SIZE OF ADTNUM -
THE TOTAL NUMBER OF RECORDS ON DISK). THEN THE QMSK
EXTNESIONS (IF ANY) ARE READ INTO THE FREE STORAGE
AREA, DOUBLE-WORD ALIGNED, AND WITH AN INTEGRAL
NUMBER OF DOUBLE-WORDS IN THE READ (TO PREVENT A
POSSIBLE CHAINING CHECK WHEN RUNNING ON CP), AND THEN
MOVED TO THE PROPER PLACE IN THE QMSK BUFFER: THE
FIRST 215 BYTES OF THE QMSK ARE THEN MOVED FROM THE
MFD TO THE QMSK IN CORE. (IF THE QMSK IS LESS THAN
215 BYTES, ONLY THE CORRECT NUMBER OF BYTES IS
MOVED). WHEN THROUGH, THE QMSK IS LAID OUT IN CORE
AS ONE CONTIGUOUS TABLE, WITH AN INTEGRAL NUMBER OF
BYTES, PADDED (IF NECESSARY) TO AN INTEGRAL NUMBER OF
DOUBLE WORDS, IN FREE STORAGE.
THE LOCATION OF THE QMSK IS OF COURSE STORED WHERE
NEEDED, AND THE OTHER COUNTS (ADTPQM1 THROUGH
ADTPQM3), COMPUTED AND STORED. FREE STORAGE IS THEN
OBTAINED FOR THE QQMSK, IF A 2314 READ/WRITE DISK AND
THE 200-BYTE QQMSK TABLE MOVED INTO POSITION FROM THE
MFD.
LASTLY, AS MENTIONED ABOVE FOR THE READ-ONLY CASES,
JUST ENOUGH FREE STORAGE IS OBTAINED FOR THE
INFORMATION ON DISK ADDRESSES CONTAINED AT THE
BEGINNING OF THE MFD TO BE KEPT IN CORE, THE CRUCIAL
DATA IS MOVED THERETO, AND THE 800-BYTE BUFFER IS
RELEASED.
IF THE DISK IS AN O/S DISK, THE DISK LABEL AND VTOC
ADDRESS ARE SAVED IN THE ADT BLOCK. A CHECK IS MADE
TO DETERMINE IF DMSROS HAS BEEN LOADED (BY A PREVIOUS
ACCESS OF AN O/S DISK) AND IF NOT DMSSTT IS CALLED TO
VERIFY THAT DMSROS TEXT EXISTS. UPON SUCCESSFUL RETURN
FROM STATE (IF NOT FOUND, AN ERROR MSG IS ISSUED),
DMSROS TEXT IS LOADED INTO HIGH STORAGE AREA WITH
PROTECT KEY OF NUCLEUS AND A BRANCH IS MADE TO THE
O/S ACCESS ROUTINE OF DMSROS TO READ THE FORMAT 4
DSCB OF THE DISK. UPON SUCCESSFUL RETURN FROM DMSROS,
CONTROL IS RETURNED TO THE CALLER. ANY OTHER ERRORS
ARE TREATED AS GENERAL LOGIN ERRORS.
TO SUMMARIZE:
FOR A READ-WRITE DISK, DMSACM READS IN ALL OF THE
USER FILE DIRECTORY EXCEPT THE FST HYPERBLOCKS AND
INITIALIZES ALL APPROPRIATE INFORMATION IN THE ACTIVE
DISK TABLE.
FOR A R/O CMS DISK, DMSACM READS IN ALL OF THE USER
FILE DIRECTORY EXCEPT THE FST HYPERBLOCKS, THE QMSK
AND QQMSK TABLES, AND THE COUNTS IN THE LATTER HALF
OF THE ACTIVE DISK TABLE ASSOCIATED WITH THE QMSK AND
QQMSK TABLES, WHICH ARE NOT NEEDED IN CORE FOR A
READ-ONLY DISK.
Calls to Other Routines
DMSFREE, DMSFRET, DMSDIOR, DMSDIOW, DMSROS