I'm working on a very simple MFS to control security - to restrict display of selected fields in a record based on User security and Field Rights as stored in a field in the same record. I have the logic working however I want verify that I am properly handling each of the GoSub CODE values for the MFS subroutine ie which CODE values do I pass on to Next.MFS, what ones do I set STATUS False$ /True$ ?

I am using the two standard OI MFS inserts - the equates and GoSub. Yes, I have the MFS PDF and AREV Tech Manual but this info appears slightly dated v my OIv3.71 equates eg which refers to select.index etc and replaces lock.semaphore with Reserved.

1. Could you email me the sample MFS shells.

2. Are there any other good MFS examples which you or others could provide? I am most interested in some of the cool things that one can do with MFS eg controlling select lists to filter out "restricted" records, audit trails and record_change trails. Also the possibility of maintaining custom indexes for quick retrieval akin to Quickdex for fields other than key etc

Richard Bright

[email protected]

I want verify that I am properly handling each of the GoSub CODE values for the MFS subroutine ie which CODE values do I pass on to Next.MFS, what ones do I set STATUS False$ /True$ ?

There are three that you do NOT next-fs on: Install, Flush, and UnlockAll.

Be careful on Install. The system may not have finished starting up by that time so you are limited in what you can do.

Remember that your MFS runs in a very strict file-io context. Don't do any PS calls for example (get/set properties).

I am using the two standard OI MFS inserts - the equates and GoSub. Yes, I have the MFS PDF and AREV Tech Manual but this info appears slightly dated v my OIv3.71 equates eg which refers to select.index etc and replaces lock.semaphore with Reserved.

Use the OI one if possible. You most probably will not be implementing the .index stuff anyway.

1. Could you email me the sample MFS shells.

You are in luck. Apparently I did just that for someone else because I had the following code hanging around:

<code>
subroutine Log_MFS(Code, BFS, Handle, Name, Fmc, Record, Status)

*****************************************************************************
*
* Name       :  Log_MFS
* Description:  Logs changes to records in various tables
*
* History (Date, Initials, Notes)
*   05/13/97  cp   Original programmer (XQ_MFS).
*
*****************************************************************************

$insert Logical
$insert FSErrors_100

equ MFS_NAME$ to "LOG_MFS"

$insert File.System.OnGosub
return



****************************************
* store file name in the returned handle
****************************************
Open.File:
  Table   =Name 1,"*"
  FSHandle=Handle

  gosub NextFS
  if Status then
    Record := "*": Table
  end
return


**************************
* record is being modified
**************************
Write.Record:
  Table   =Handle -1,"B*"
  FSHandle=Handle 1,col1()-1

  gosub NextFS
  if Status then
    gosub LogWrite
  end
return


*************************
* record is being deleted
*************************
Delete.Record:
  Table   =Handle -1,"B*"
  FSHandle=Handle 1,col1()-1

  gosub NextFS
  if Status then
    gosub LogDelete
  end
return


*********************************
* log transaction for all records
*********************************
ClearFile:
  Status  =TRUE$
  Table   =Handle -1,"B*"
  FSHandle=Handle 1,col1()-1
  FSList  =delete(BFS, 1, 1, 1)
  fTable  =FSList: @vm: FSHandle

  select fTable
  eof=FALSE$

  transfer Name to HoldName
  loop
    readnext Name else eof=TRUE$
  until eof
    gosub LogDelete
  while Status
  repeat
  transfer HoldName to Name

  if Status then
    gosub NextFS
  end
return


*********************************
* non-chained filing system calls
*********************************
Flush:
Unlock.All:
  Record="
Install:
  Status=TRUE$
return


*****************************
* chained filing system calls
*****************************
Read.Record:
ReadO.Record:
Lock.Record:
Unlock.Record:
Select:
ReadNext:
ClearSelect:
Record.Count:
Create.Index:
Delete.Index:
Update.Index:
Select.Index:
ReadNext.Index:
Omni.Script:
  Table   =Handle -1,"B*"
  FSHandle=Handle 1,col1()-1
  gosub NextFS
return

Reserved:
  @file.error=FS_NOT_IMPL$: @fm: Code: @fm: MFS_NAME$
  Status=FALSE$
return

Create.File:
Rename.File:
Move.File:
Delete.File:
Remake.File:
Open.Media:
Create.Media:
Read.Media:
Write.Media:
Close.Media:
  FSHandle=Handle
  gosub NextFS
return


*****************************
* execute filing system chain
*****************************
NextFS:
  FSList=delete(BFS, 1, 1, 1)
  NextFS=FSList
  if len(NextFS) then
    call @NextFS(Code, FSList, FSHandle, Name, Fmc, Record, Status)
  end
return


******************************************************************************


*************************
* log record modification
*************************
LogWrite:
  gosub GetOrigRecord
  begin case
    case Table=INVOICES"
      if Record # OrigRecord then
        * do change processing here
      end

    case Table=PURCHASE_ORDERS"
      if Record # OrigRecord then
        * do change processing here
      end
  end case
return


*********************
* log record deletion
*********************
LogDelete:
  gosub GetOrigRecord

  * see LogWrite above for an example
return


***********************
* load "current" record
***********************
* Name       in  - record key
* OrigRecord out - original record or null
GetOrigRecord:
  FSList=delete(BFS, 1, 1, 1)
  NextFS=FSList
  call @NextFS(READ.RECORD, FSList, FSHandle, Name, "", OrigRecord, Exists)
  if Exists else
    OrigRecord="
  end
return

</code>

2. Are there any other good MFS examples which you or others could provide? I am most interested in some of the cool things that one can do with MFS eg controlling select lists to filter out "restricted" records, audit trails and record_change trails. Also the possibility of maintaining custom indexes for quick retrieval akin to Quickdex for fields other than key etc

Here's one that collates together multiple source files into a virtual SYSPROCS for our GOLD source system:

<code>
subroutine IT_SysProcs_Mfs(Code, BFS, Handle, Name, Fmc, Record, Status)

*****************************************************************************
*
* Name       :  IT_SysProcs_Mfs
* Description:  Modified Filing System for OpenInsight "Gold" SysProcs table
*
* History (Date, Initials, Notes)
*   10/21/97  cp   Original programmer.
*
*****************************************************************************

$insert Logical
$insert FSErrors_100

equ MFS_NAME$ to "IT_SYSPROCS_MFS"

common //MFS_NAME$// f_Arev_BP, f_Rev_BP, f_Rev_Hidden, f_Rev_Procs, f_Notes_Procs

$insert File.System.OnGosub
return



****************************
* open other required tables
****************************
Open.File:
  Status=TRUE$
  open "AREV_BP"     to f_Arev_BP     else Status=FALSE$
  open "REV_BP"      to f_Rev_BP      else Status=FALSE$
  open "REV_HIDDEN"  to f_Rev_Hidden  else Status=FALSE$
  open "REV_PROCS"   to f_Rev_Procs   else Status=FALSE$
  open "NOTES_PROCS" to f_Notes_Procs else Status=FALSE$

  if Status then
    gosub NextFS
  end
return


*******************************
* unchained filing system calls
*******************************
ReadO.Record:
Read.Record:
  gosub NextFS
  if not(Status) and @file.error=FS_REC_DNE$ then
    [email protected]
    Hold_Status     =status()

    Exists ="
    Tables =REV_BP": @fm: "REV_HIDDEN"   : @fm: "NOTES_PROCS": @fm: "REV_HIDDEN"             : @fm: "REV_PROCS": @fm: "REV_HIDDEN"        : @fm: "AREV_BP": @fm: "REV_HIDDEN"
    Handles=f_Rev_BP: @fm: f_Rev_Hidden   : @fm: f_Notes_Procs: @fm: f_Rev_Hidden             : @fm: f_Rev_Procs: @fm: f_Rev_Hidden        : @fm: f_Arev_BP: @fm: f_Rev_Hidden
    Keys   =Name    : @fm: "REV_BP/": Name: @fm: Name         : @fm: "OINOTES_SYSPROCS/": Name: @fm: Name       : @fm: "OE_SYSPROCS/": Name: @fm: Name     : @fm: "AREV.BP/": Name
    cKeys  =count(Keys, @fm) + (Keys # "")
    dim Records(cKeys)

   * find all copies of the requested record
    for i=1 to cKeys
      fTemp=Handles[i]
      read Temp from fTemp, Keys[i] then
        Records(i)=Temp
        Exists[i] =TRUE$
      end else
        Records(i)="
        Exists[i] =FALSE$
      end
    next i

    if index(Exists, TRUE$, 1) then
     * weed out duplicates
      for i=1 to cKeys
        if Exists[i] then
          Temp=*":Records(i)
          for j=i+1 to cKeys
            if "*":Records(j)=Temp then
              Exists=FALSE$
            end
          next j
        end
      next i

     * determine which record to return; list all different records found
      First   ="
      Text    =**************************************************"
      Text=*"
      Text=* This record does not exist in the SYSPROCS table"
      Text=*"
      Text=* ": fmt("Table", "L#20"): " Key"
      Text=* ": str("-", 20): " ": str("-", 20)
      for i=1 to cKeys
        if Exists[i] then
          Text=* ": fmt(Tables[i], "L#20"): " ": Keys[i]
          if First else
            First=i
            Text := " (this record)"
          end
        end
      next i
      Text=*"
      Text=**************************************************": @fm: @fm: @fm

      record     =Text: Records(First)
      status     =TRUE$
      @file.error="
      status()   =0
    end else
      @file.error=Hold_AtFileError
      status()   =Hold_Status
    end
  end
return


*******************************
* unchained filing system calls
*******************************
Flush:
Unlock.All:
  Record="
Install:
  Status=TRUE$
return


*****************************
* chained filing system calls
*****************************
Write.Record:
Delete.Record:
Lock.Record:
Unlock.Record:
Select:
ReadNext:
ClearSelect:
Record.Count:
Create.Index:
Delete.Index:
Update.Index:
Select.Index:
ReadNext.Index:
Omni.Script:
  gosub NextFS
return

ClearFile:
Reserved:
  @file.error=FS_NOT_IMPL$: @fm: Code: @fm: MFS_NAME$
  Status=FALSE$
return

Create.File:
Rename.File:
Move.File:
Delete.File:
Remake.File:
Open.Media:
Create.Media:
Read.Media:
Write.Media:
Close.Media:
  gosub NextFS
return


*****************************
* execute filing system chain
*****************************
NextFS:
  FSList=delete(BFS, 1, 1, 1)
  NextFS=FSList
  if len(NextFS) then
    call @NextFS(Code, FSList, Handle, Name, Fmc, Record, Status)
  end
return

</code>

Cameron Purdy

Revelation Software

Cam,

Thanks for the MFS code. While I had the MFS working fine (thusfar) I am pleased to clarify some of the issues plus your code expanded / filled in some gaps.

I forgot to ask if there are general rules for where the MFS should be installed in the MFS / BFS chain (depending on the nature of the MFS. That is, the manual suggests that a simple MFS such as handling field level security (blanking out field) is installed at the beginning of the chain. But presumably the SI.MFS will come first, and the BFS/RTP57 comes last ie

SI.MFS MY_TABLE_MFS*MYAPP RTP57

Richard Bright

You can solve that question simply by asking the question: should SI.MFS see the data before or after you filter it. I would assume (in most cases) that you would want SI.MFS to see the data BEFORE you start whacking it on a user-by-user basis, since otherwise your indexes will be crap.

Cameron Purdy

Revelation Software

Hello all,

I was looking through Cameron's MFS code to see if I was missing anything in our audit MFS. For those who will be venturing into the world of MFS, pay careful attention to Cameron's code regarding Record.Count and Clearfile. The MFS pdf documentation does not list these items as needing to have the file name removed from the handle before continuing to the next FS.

I also have a question regarding the *.Index operations. I haven't found any documentation on these but noticed they require the file name being removed from the handle as well. I have updated our MFS logic, but I haven't ever encountered a problem with this before.

Is there any documentation on these operations?

[email protected]

SRP Computer Solutions

The issue is really one of semantics here. Technically, nothing should be removed from the handle except what the MFS itself puts there. Each MFS should pass the handle back as it found it. For example, a common practive in some MFSs is to place the file name in the handle so a program has easy access to the file name. There is nothing wrong with this practice, provided the MFS remembers to remove the name before calling @NEXTFS.

Cameron is relying on a bit of trickery, which will not always work, (sorry Cam, you know I rarely try to correct you). Since your MFS can theoretically be anywhere on the FS chain, the handle can be in any format. Cameron is relying on knowing his system, what MFSs are available, what structure they are using and what version of ARev or OI he is running.

This touches on the other issue in dealing with handles inside an MFS. Revelation has occasionally changed the structure of the handle as returned from RTP57 and various system MFSs (SI.MFS and QUICKDEX.MFS come to mind). MFSs which make assumptions about the structure of the handle could break on different versions of ARev or OI.

So, back to Cameron's program. What he's doing in the ClearFile section is attempting to clear out the various log records created for each record in the base file. To do that, he needs to process each record in the base file before the file is cleared. So, he's performing a simple R/BASIC select to obtain all the record keys.

A simple R/BASIC select requires a valid handle for processing. This means Cameron has two options. He can either re-open the file to obtain the "correct" handle or he can use his superior knowledge of the system to generate a valid simple handle.

The safest course of action is to open the file. The fastest file access would be to generate a simple handle.

In general though, unless you want access to the current file from within the MFS, you should never have to manipulate the current handle.

I'll be happy to elaborate further if you wish. MFSs just might be my favourite subject to pontificate on.

The Sprezzatura Group

World leaders in all things RevSoft

Well Mr. Sprezzatura Group,

Even with the threat of pontification looming large I would point out that the filename-in-the-handle-thing and removing it as the code did should work well, because each MFS (both the one you write and the ones outside of yours in the chain) MUST provide the inner FS with the handle that the inner FS returned from OPEN.FILE. In other words, the code I wrote MUST remove the filename from the handle because it added it to the handle returned from the inner FS's OPEN.FILE call. As long as everyone obeys the rules, it works beautifully. That said, I have seen some cases where file handle composition was assumed to be in a particular format and was thus parsed directly assuming that no MFS had added information to it. Those cases, BTW, are where OMNI.SCRIPT is supposed to be used, since you can ask the FS a question specific to that FS without having to know anything about the handle structure, and the outer MFS's are supposed to pass the questions down that are not intended for them. At least that is ho

w I remember it.

Cameron Purdy

Revelation Software

Cam,

Thanks for confirming the issue of 'place of MFS in chain'. Also Sprez's discussion of manipulation of the file handle has been most interesting. Working off your Log example code I had been hesitant, not knowing the end purpose of the handle manipulation and so had eliminated it from my MFS re-write. I will now revisit this issue and look to see if I can exploit that feature. The big plus - is now understanding WHY the extra code is there.

Richard Bright

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