[Firebird-devel] On-disk structure trouble

[Cosmin P. <cos...@ad...>]

Hello everyone, this is my first mail to the "developer" list. I'm not
working on the Firebird code-base (in fact I can't even compile it,
being able to compile it myself would make my troubles about a 1000
times smaller).

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I'm working on a tool to help me recover a few corrupted databases that
can't be fixed with "mend" (mend makes it worst). I'm trying to build a
program that takes a FDB file and "dumps" it's contents to a new FDB
file, doing direct disk access. I'm trying this because I'd rather have
99% good data + 1% corrupted data out of the database, and at the moment
"mend" gives 0% data (it deletes tables).

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So far I've been able to do the basics: Open the file, read the system
tables - RDB$FIELDS, RDB$RELATION_FIELDS so I've certainly done some
things right :-) By now I can re-create all the tables (that's proof I
was able to properly read RDB$FIELDS, RDB$RELATIONS and
RDB$RELATION_FIELDS) and I'm starting on pumping data. Here's where my
luck ends.

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I need some info on how Firebird stores it's data types on disk. How
does NUMERIC(18,4) look on disk? How about DATE? TIMESTAMP?
NUMERIC(3,2)? VARCHAR seems to give me trouble too.

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If anyone could point me towards a "H" or "C" or "CPP" file that does
some work on those types so I have a starting point, I'd be eternally
grateful. So far I used a "grep" variant to search for key identifiers,
starting from "ods.h". With those base types I have no idea where to
start my search from.

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--

Thanks,

Cosmin Prund

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