MFS PROGRAMMING & USAGE
| Published By | Date | Version | Knowledge Level | Keywords |
|---|---|---|---|---|
| Revelation Technologies | 14 NOV 1989 | 2.X | EXPERT | %RECORDS%, @-variables, @LIST.ACTIVE, @NEXT.FS, sample, program, Next, Aborting, Disabling, Accessing, file+, also, Calling,, Direct, call, different, files, Accounts,, Non-SYSPROG, Arguments, modifying+, names, Assembly, language, Attaching, after, changing, file, handle, installation, using, volume, name, Audit, trail, calling, system, argument, during, FLUSH, INSTALL, BFS,, definition, BFS-bound, Branching+, Btree, index, Buffers, caching, Bypassing, with, direct, calls, Caching, Calling, directly, from, R/BASIC, next, list, CASE, statement, Cataloging, Changing, CLEARSELECT, CODE, Compatibility, Compiling, Compression, CREATE.FILE, CREATE.MEDIA, Current, accessing, Cursors, Data, passing, De-installing, object, code, Debugger, Debugging,during, development, Decryption, Encryption, DELETE.FILE, Detaching, DICT.MFS, Dictionary, problems, with+, current, Direction,READNEXT, function+, Dispatching+, Environmental, Bond, Example |
MFS's - PART VIII
CREATE.FILE
The CREATE.FILE call uses the FMC argument to pass file creation options to the BFS. For example, the various TCL-level options that can be specified at the time a Linear Hash file is being created are passed to RTP57 via the FMC argument.
The file creation options are passed as a two-field dynamic array. The first field contains the TCL command line options, delimited with value marks. The second field contains the literal character "D" if a dictionary file is being created.
Unless a user specifies an explicit DATA or DICT parameter, the TCL MAKEFILE command will generate two calls to the filing system. The first creates the data portion of the file, and the second generates the dictionary portion. When a dictionary is being created, the system generates additional calls to create the @CRT record in the dictionary.
NonVolume Media Calls
Three media calls are available even if the MFS is installed only on the file, and not on the volume:
MOVE.FILE RENAME.FILE DELETE.FILE
As with other calls, these can be disabled by setting STATUS to false and returning.
Record Count
A special call is available for BFSs to return a count of the records in a file. This call was designed for filing systems such as Linear Hash (RTP57) that maintain a record count directly in the file. This call is available only through the system subroutine GET.RECCOUNT (or directly).
If the filing system is not able to fulfill the request for a record count, it will return a status value of zero. This value is in turn passed back via the second argument of GET.RECCOUNT as a "valid" flag. As of Version 1.13 of Advanced Revelation, only Linear Hash files created under Version 1.13 or later of Advanced Revelation can fulfill a request for a record count using stored arguments. Other filing systems, including Linear Hash from earlier versions of Advanced Revelation, will return a status of false.