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