Ninneman. Eric received Don Woods's encouragement to update and ship
the game; Jason signed on early in the process to help. The assistance
of Peje Nilsson in restructuring some particularly grotty gotos is
-gratefully acknowledged.
+gratefully acknowledged. Petr Voropaev contributed fuzz testing. Aaron
+Traas did a lot of painstaking work to improve test coverage.
== Nomenclature ==
suite for the game. Any log captured with -l (and thus containing
a "seed" command) will replay reliably, including random events.
-The adventure.text file is no longer required at runtime. Instead, it
-is compiled at build time to a source module containing C structures,
-which is then linked to the advent binary.
+The adventure.text file is no longer required at runtime. Instead, an
+adventure.yaml file is compiled at build time to a source module
+containing C structures, which is then linked to the advent
+binary. The YAML is drastically easier to read and edit than
+the old ad-hoc format of adventure.txt.
The game-save format has changed. This was done to simplify the
FORTRAN-derived code that formerly implemented the save/restore
checksumming have been discarded - it's pointless to try
tamper-proofing saves when everyone has the source code.
+A -r command-line been added. When it is given (with a file path
+argument) it is functionally equivalent to a RESTORE command.
+
== Translation ==
The 2.5 code was a mechanical C translation of a FORTRAN original.
Jason Ninneman and I have moved it to what is almost, but not quite,
idiomatic modern C. We refactored the right way, checking correctness
against a comprehensive test suite that we built first and verified
-with coverage tools (we have 88% coverage, with the remaining 12%
-confined to exception cases that are difficult to reach). This is
+with coverage tools (we now have over 95% coverage, with the remaining
+confined to exception cases that are very difficult to reach). This is
what you are running when you do "make check".
-This move entailed some structural changes. The most important was
-the refactoring of over 350 gotos into if/loop/break structures. We
-also abolished almost all shared globals; the main one left is a
-struct holding the game's saveable/restorable state.
+In the process we found and fixed a few minor bugs. Most notably, reading
+the relocated Witt's End sign in the endgame didn't work. Behavior when
+saying the giant's magic words outside his room wasn't quite right either.
+
+The move to modern C entailed some structural changes. The most
+important was the refactoring of over 350 gotos into if/loop/break
+structures. We also abolished almost all shared globals; the main one
+left is a struct holding the game's saveable/restorable state.
The original code was greatly complicated by a kind of bit-packing
that was performed because the FORTRAN it was written in had no string
verb was one of these words, and what would be string operations in a
more recent language were all done on sequences of these words.
-We are still in the process of removing all this bit-packing cruft
-in favor of proper C strings. C strings may be a weak and leaky
-abstraction, but this is one of the rare cases in which they are
-an obvious improvement over what they're displacing...
+We have removed all this bit-packing cruft in favor of proper C
+strings. C strings may be a weak and leaky abstraction, but this is
+one of the rare cases in which they are an obvious improvement over
+what they're displacing...
+
+We have also conducted extensive fuzz testing on the game using
+afl (American Fuzzy Lop). We've found and fixed some crashers in
+our new code (which occasionally uses malloc(3)), but none as yet
+in Don's old code (which didn't).
The code falls short of being fully modern C in the following
ways:
We don't need whatever minor performance gains this might collect,
and the choice to refrain will make forward translation into future
languages easier.
-* There are a few gotos left that resist restructuring; all of these
- are in the principal command interpreter function implementing its
- state machine.
+
+* There are a few gotos left that resist restructuring; all are in the
+ principal command interpreter function implementing its state
+ machine.
* Linked lists (for objects at a location) are implemented using an array
of link indices. This is a surviving FORTRANism that is quite unlike
to fix it because doing so would (a) be quite difficult, and (b)
compromise forward-portability to other languages.
-* The code still has an unfortunately high density of magic numbers - in
- particular, numeric object and room IDs. There are plans to fix this.
-
-* Much of the code still uses FORTRAN-style uppercase names.
+* Much of the code still assumes one-origin array indexing. Thus,
+ arrays are a cell larger than they strictly need to be and cell 0 is
+ unused.
* The code is still mostly typeless, slinging around machine longs
like a FORTRAN or BCPL program. Some (incomplete) effort has been made
to introduce semantic types.
+We have made exactly one minor architectural change. In addition to the
+old code's per-object state-description messages, we now have a per-object
+message series for state *changes*. This makes it possible to pull a fair
+amount of test out of the arbitrary-messages list and associate those
+mesages with the objects that conceptually own them.
+
// end
projects / open-adventure.git / blobdiff