From: Tomas Frydrych (firstname.lastname@example.org)
Date: Sat May 17 2003 - 06:44:13 EDT
The way we generate id's for various things in the document, such as
headers, footnotes and lists is a real mess; in our code there are
three different methods used to create what are are supposed to be
1. using UT_rand: randomness does not guarantee uniqueness, as the
generator can produce duplicate numbers before exhausting all
possibilities. It creates the impression of uniqueness, which will
sooner or later come to haunt us.
2. Using sequential generation: this is used in bits and pieces of
our importer code; it guarantees uniquness while importing, but once
we enter editing mode, we have lost control. Further more, as there
is no relationship between the state of the rand generator used in
the editing mode and the id's sequentially generated on import, our
chances of non-uniquness are incereased.
3. reusing id's stored in the imported document; same problem as (2).
Neither of the three methods above is good enough, and the present
state of things has to change before the 2.0 release. The bottom
line: unique id's need to be generated on document level and have to
So I have implemented UT_UniqueId class (ut_misc.h/cpp) and
PD_Document methods getUID(type) and setMinUID(type, min), which I
will commit as soon as I can get into the CVS, and I am going to
start working on moving all our code to using these.
For the mainteners of importers, this is how it will work: (1) when a
unique id is to be generated it will be generated using the
PD_Document::getUID() method. (2) if a unique numerical id stored in
the document is being reused, the importer needs to call
PD_Document::setMinUID() to ensure that any future generated id's
will be greater than this. (3) if a unique alphanumerical id stored
in the document is being reused, the importer needs to take similar
steps to ensure that this id cannot be reduplicated in the editing
Exporters: stick to numerical id's as much as possible, it will make
our life much simpler.
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