Subj : ISAM variable-length demark?
To   : All
From : Mike Luther
Date : Thu Mar 08 2001 12:30 am

The simple ISAM I'm testing works.  The record file is all variable length 
ASCII text strings.  Currently in BASIC, the record has no ASC(0) characters in 
it, but in moving it to C/C++ or something else, that might change, at least 
for the final character for a given page.  The record is a collage of many 
variable length strings, including CR/LF's, tabs.  It's a printer text image of 
page after page of whatever was printed on the page.  Essentially it's an 
indexed book to which the keys let you print any page on demand.

I have to be able to scan it later and reconstruct the key(s) file(s), should 
they get lost or grunged.

What record demark character (group) would be a good choice to use to break up 
the record parade so that I can brute force the file to reconstruct the keys?  
Obviously, this sort of thing has been thought about long before this,but it's 
new to me...

For my curious reasons, I'd even settle, I think, for the old WordStar page 
break deal.  It looks like:

 000BD0  20 61 73 20 74 68 65 20 61 62 6F 76 65 0D 0A 1D   as the above   
 000BE0  20 00 0B F0 00 37 00 00 00 90 33 01 00 00 00 00     7
 000BF0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20
 000C00  00 1D 0D 8A 54 68 69 73 20 A0 62 65 6C 69 65 76       e This

Looks to me like it is a chunk of code starting with ASC(1D) and ASC(20) and 
ending with ASC(0D) and ASC(8A).  However, I don't see any FF ASC(0C) in there. 
 Obviously, this 37 byte block holds information, most likely page number, 
things like that.  In that this block quoted above is the actual page break 
between page one and page two, is that ASC(01) in the above the start of either 
a short or long integer for the page numher, Big Indian -Little Indian or what?

Anyone here recall how to read W/S page break blocks or know where to get that 
insight?

It would be nice to have a defined spacer block between the records from which 
to get the pointers to the previous record, et. al.

Anyone have any thoughts.  I've picked W/S apart years ago, but not this part 
of it.

Thanks.


Mike @ 1:117/3001

--- Maximus/2 3.01
 * Origin: Ziplog Public Port (1:117/3001)

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