Subj : Re: store collections of strings in tdb or gdbm
To   : comp.programming
From : jburgy
Date : Sat Oct 08 2005 08:01 am

Lasse Kliemann wrote:
> Greetings,
>

Hi there,

> my data is organized as follows:
>
> - There are several records.
> - Each record consists of a fixed number of strings.

[snip]

> My idea so far for each record:
>
> - Get the decimal representation of all the lengths of the strings in
>   the record.
> - Write these into dptr, as null-terminated strings.
> - Then write all the strings into dptr.
>
> It is obvious how to get the strings back from this encoding.
>
>
> My questions now are:
>
> - How elegant is my approach?

It sounds just plain wrong. I know nothing about tdb so feel free to
diss my comment but the way you would normally do this in a relational
database is like this

record_id | string_id | string_text
-----------------------------------
0         | 0         | 'foo'
0         | 1         | 'bar'
0         | 2         | 'baz'
1         | 3         | 'qux'
1         | 4         | 'quux'
1         | 5         | 'quuux'

Hopefully you get the picture. If tdb is as trivial as the struct you
showed leads me to believe, you may need two tables to achieve this:
one stores the strings (with one string per record, no worries, these
records have nothing to do with yours), the other the correlation
between string_id and record_id. Something like

char *string_text[] = { "foo", "bar", "baz", "qux", "quux", "quuux",
.... };
int record_id = { 0, 0, 0, 1, 1, 1, .... };

You catch my drift?

> - Is the conversion into the decimal representation necessary, or can I
>   write the lengths of the strings as unsinged ints into dptr? Would
>   this be portable?

If you insist on going with your idea: showing unsigned ints into a
char* is not portable, google endianness.

> - Hasn't this been done before and exists in form of a library?

I don't believe so, people usually use a variation of what I'm
describing

Good luck and let me now how it goes,

Jan

.