= Open Adventure Maintainer's Notes =
by Eric S. Raymond
+// SPDX-FileCopyrightText: (C) Eric S. Raymond <esr@thyrsus.com>
+// SPDX-License-Identifier: CC-BY-4.0
In which we explain what has been done to this code since Don Woods
authorized us to ship it under an open-source license. There's a
The principal maintainers of this code are Eric S. Raymond and Jason
Ninneman. Eric received Don Woods's encouragement to update and ship
-the game; Jason signed on early in the process to help.
+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. Petr Voropaev contributed fuzz testing and
+code cleanups. Aaron Traas did a lot of painstaking work to improve
+test coverage, and factored out the last handful of gotos. Ryan
+Sarson nudged us into fixing a longstannding minor bug in the
+handling of incorrect magic-word sequebcesm,
== Nomenclature ==
== Philosophy ==
Extreme care has been taken not to make changes that would alter the
-logic of the game as we received it from Don Woods. By policy, all
-user-visible changes must be revertible with the -o (oldstyle) option.
-
-It is a goal of this project to exactly preserve the *behavior* of
-430-point Adventure, but the implementation of it is fair game for
-improvement. In particular, we are concerned to move it to a form that
-is (a) readable, and (b) friendly to forward translation to future
-languages. It has already survived a move from FORTRAN to C; a future
-as a Python or Go translation seems possible, even probable.
+logic of the game as we received it from Don Woods, except to fix
+glitches that were clearly bugs. By policy, all user-visible
+changes to gameplay must be revertible with the -o (oldstyle) option.
+
+It is a goal of this project to exactly preserve the *intended
+behavior* of 430-point Adventure, but the implementation of it is fair
+game for improvement. In particular, we are concerned to move it to a
+form that is (a) readable, and (b) friendly to forward translation to
+future languages. It has already survived a move from FORTRAN to C; a
+future as a Python or Go translation seems possible, even probable.
+
+Compatibility with the 2.5 source we found has been checked by
+building a version patched minimally to support the seed command and
+running it against the entire test suite, which has 100% code
+coverage.
== Functional changes ==
+Bug fixes:
+
+* The caged bird used to be counted as two items in your inventory.
+
+* Reading the relocated Witt's End sign in the endgame didn't work right.
+
+* Oyster was readable after first gotten even when not carried.
+
+* Response to an attempt to unlock the oyster while carrying it was incorrect.
+
+* Behavior when saying the giant's magic words before having seen them
+ wasn't quite correct - the game responded as though the player had
+ already read them ("...can't you read?"). The new message is "Well,
+ that was remarkably pointless!" The -o option reverts this change.
+
+* Attempting to extinguish an unlit urn caused it to lose its oil.
+
+* "A crystal bridge now spans the fissure." (progressive present) was
+ incorrect most places it appeared and has been replaced by "A crystal
+ bridge spans the fissure." (timeless present).
+
+* A few minor typos have been corrected: absence of capitalization on
+ "Swiss" and "Persian", inconsistent spelling of "imbedded" vs. "embedded",
+ "eying" for "eyeing", "thresholds" for "threshholds".
+
+* Under odd circumstances (dropping rug or vase outdoors) the game could
+ formerly say "floor" when it should say "ground" (or "dirt", or something).
+
+Enhancements:
+
By default, advent issues "> " as a command prompt. This feature
became common in many variants after the original 350-point version,
but was never backported into Crowther & Woods's main line before now.
-The "-o" (oldstyle) version reverts the behavior.
+The "-o" (oldstyle) option reverts the behavior.
+
+There is a set of standard one-letter command aliases conventional in modern
+text adventure games; 'l' and 'x'; for 'look' (or 'examine'), 'z' to do nothing
+for a turn, 'i' for 'inventory', 'g' for 'get', and 'd' for 'drop'. The 'd'
+alias collides with 'd' for 'down', but the others have been implemented.
+The "-o" (oldstyle) option disables them.
+
+Unrecognized words are no longer truncated to 5 characters and
+uppercased when they are echoed. The "-o" (oldstyle) option restores
+this behavior.
A "seed" command has been added. This is not intended for human use
but as a way for game logs to set the PRNG (pseudorandom-number generator) so
that random events (dwarf & pirate appearances, the bird's magic word)
will be reproducible.
+A "version" command has been added. This has no effect on gameplay.
+
+The text displayed by the "news" command has been updated.
+
A -l command-line option has been added. When this is given (with a
file path argument) each command entered will be logged to the
specified file. Additionally, a generated "seed" command will be put
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 game-save format has changed. This was done to simplify
-FORTRAN-derived code that formerly implemented these functions;
-without C's fread(3)/fwrite() and structs it was necessarily pretty
-ugly by modern standards. Encryption and checksumming have been
-discarded - it's pointless to try tamper-proofing saves when everyone
-has the source code.
+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
+functions; without C's fread(3)/fwrite() and structs it was
+necessarily pretty ugly by modern standards. Encryption and
+checksumming have been discarded - it's pointless to try
+tamper-proofing saves when everyone has the source code. However
+the game still integrity-checks savefiles on resume, including an
+abort if the endianness of the restoring machine does not match that of
+the saving machine. There is a magic-cookie header on the saves so
+in theory they could be identified by programs like file(1).
+
+Save and resume filenames are stripped of leading and trailing
+whitespace before processing.
+
+A -r command-line option has been added. When it is given (with a file
+path argument) it is functionally equivalent to a RESTORE command.
+
+An -a command-line option has been added (conditionally on
+ADVENT_AUTOSAVE) for use in BBS door systems. When this option is
+given, the game roads from the specified filename argument on startup
+and saves to it on quit or a received signal. There is a new nmessage
+to inform the user about this.
+
+The game can be built in a mode that entirely disables save/resume
+(-DADVENT_NOSAVE). If the game had been built this way, a diagnostic is
+emitted if you try to save or resume.
== Translation ==
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 comprehesive test suite that we built first and verified with
-coverage tools. This is what you are running when you do "make check".
+against a comprehensive test suite that we built first and verified
+with coverage tools (there is effectively 100% code coverage). This is
+what you are running when you do "make check".
-This move entailed some structural changes. The most important was
-the refactoring of 355 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 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
type. Text from the adventure.text file was compiled into sequences
of sixbit code points in a restricted character set, packed 5 to a
-32-bit word (it seems clear from the code that words were originally
+32-bit word (and it seems clear from the code that words were originally
*6* chars each packed into a PDP-10 36-bit word). A command noun or
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...
-The code falls a short of being fully modern C in the following
+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).
+
+After version 1.11, correctness was carefully checked against the
+behavior of a binary from before the big refactoring.
+
+The code falls short of being fully modern C in the following
ways:
* We have not attempted to translate the old code to pointer-based
and the choice to refrain will make forward translation into future
languages easier.
-* There are 19 gotos left that resist restructuring; all of these are
- in the principal command interpreter function implementing its state
- machine. A 21st, a two-level loop breakout, is not reducible even
- in principle.
-
* Linked lists (for objects at a location) are implemented using an array
of link indices. This is a surviving FORTRANism that is quite unlike
normal practice in C or any more modern language. We have not tried
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.
+* 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.
+
+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 text out of the arbitrary-messages list and associate those
+messages with the objects that conceptually own them.
+
+== Development status ==
-* 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 consider this project finished. All issues and TODOs have been
+cleared, behavior has been carefully checked against original ADVENT,
+no future demand for new features is expected, and the test suite has
+100% code coverage. If new bugs appear as the toolchain bit-rots out
+from under underneath, we will fix those problems.
// end
projects / open-adventure.git / blobdiff