[Mybusinessbasic-devel] Thoughts on file types and I/O

[Michael S. L. <mi...@ha...>]

I'm gathering my thoughts before creating the specification for file I/O and
was wondering if anyone wanted to throw their ideas into the mix.

I imagine that the SORT and DIRECT file types will be added first as they
will be the least controversial.  ;-)

Here are my thoughts so far.  Please comment.

1)  Indexed files should be easy enough to implement using either standard
file I/O or with some of the functions from the PBL Base functions.

2)  The "Keyed" file type can be used to implement SORT files.

3)  The "ISAM" file type can be used to implement DIRECT files.

4)  The "ISAM" file type can also be used to implement MULTI files; however,
new code may need to be added to the library depending on the features we
will want (It's been a long time but if I recall correctly, the MULTI class
will inherit the ISAM class and add onto it).

5)  We should add a "DIR=" function to be used in READ statements that will
indicate the direction of the read.  The default is to be "1" indicating
that the next record should be read.  Other possible values include "-1" to
read the previous record, "0" to re-read the current record, you get the
idea.

6)  Fields in Multi-keyed files should be named and access should be
permitted by name as well as by field number.  For instance if field number
8 in a file is named "Partnum" then an IOLIST could be written as either
"IOLIST #8=PARTNUM$" or "IOLIST #PARTNUM=PART$" or more traditionally as
"IOLIST *,*,*,*,*,*,*,PART$"

7)  Fields in direct files should not be named and access should be
permitted only by field number.  For instance if field number 8 in a file is
named "Partnum" then an IOLIST could be written as either "IOLIST
#8=PARTNUM$" or more traditionally as "IOLIST *,*,*,*,*,*,*,PART$"

8)  The key fields in multi-keyed files can be used in the "KEY=" function
to specify which of the keys to use for access.  For instance if the
"Partnum" field is designated as a key field then a read command could be
written as follows "READ (1,KEY=#PARTNUM=PART$)A1$,A2$,A3$..." or as "READ
(1,KEY=#8=PART$)A1$,A2$,A3$..."

-- 
Michael St. Laurent
Hartwell Corporation