1 = Open Adventure Maintainer's Notes =
3 // SPDX-FileCopyrightText: Eric S. Raymond <esr@thyrsus.com>
4 // SPDX-License-Identifier: CC-BY-4.0
6 In which we explain what has been done to this code since Don Woods
7 authorized us to ship it under an open-source license. There's a
8 separate link:history.html[history] describing how it came to us.
12 The principal maintainers of this code are Eric S. Raymond and Jason
13 Ninneman. Eric received Don Woods's encouragement to update and ship
14 the game; Jason signed on early in the process to help. The assistance
15 of Peje Nilsson in restructuring some particularly grotty gotos is
16 gratefully acknowledged. Petr Voropaev contributed fuzz testing and
17 code cleanups. Aaron Traas did a lot of painstaking work to improve
18 test coverage, and factored out the last handful of gotos. Ryan
19 Sarson nudged us into fixing a longstannding minor bug in the
20 handling of incorrect magic-word sequebcesm,
24 This project is called "Open Adventure" because it's not at all clear
25 to number Adventure past 2.5 without misleading or causing
26 collisions. Various of the non-mainline versions have claimed to be
27 versions 3, 4, 5, 6, 7 and for all I know higher than that. It seems
28 best just to start a new numbering series while acknowledging the
31 We have reverted to "advent" for the binary to avoid a name collision
32 with the BSD Games version.
36 Extreme care has been taken not to make changes that would alter the
37 logic of the game as we received it from Don Woods, except to fix
38 glitches that were clearly bugs. By policy, all user-visible
39 changes to gameplay must be revertible with the -o (oldstyle) option.
41 It is a goal of this project to exactly preserve the *intended
42 behavior* of 430-point Adventure, but the implementation of it is fair
43 game for improvement. In particular, we are concerned to move it to a
44 form that is (a) readable, and (b) friendly to forward translation to
45 future languages. It has already survived a move from FORTRAN to C; a
46 future as a Python or Go translation seems possible, even probable.
48 == Functional changes ==
52 * The caged bird used to be counted as two items in your inventory.
54 * Reading the relocated Witt's End sign in the endgame didn't work right.
56 * Oyster was readable after first gotten even when not carried.
58 * Response to an attempt to unlock the oyster while carrying it was incorrect.
60 * Behavior when saying the giant's magic words before having seen them
61 wasn't quite correct - the game responded as though the player had
62 already read them ("...can't you read?"). The new message is "Well,
63 that was remarkably pointless!" The -o option reverts this change.
65 * Attempting to extinguish an unlit urn caused it to lose its oil.
67 * "A crystal bridge now spans the fissure." (progressive present) was
68 incorrect most places it appeared and has been replaced by "A crystal
69 bridge spans the fissure." (timeless present).
71 * A few minor typos have been corrected: absence of capitalization on
72 "Swiss" and "Persian", inconsistent spelling of "imbedded" vs. "embedded",
73 "eying" for "eyeing", "thresholds" for "threshholds".
75 * Under odd circumstances (dropping rug or vase outdoors) the game could
76 formerly say "floor" when it should say "ground" (or "dirt", or something).
80 By default, advent issues "> " as a command prompt. This feature
81 became common in many variants after the original 350-point version,
82 but was never backported into Crowther & Woods's main line before now.
83 The "-o" (oldstyle) option reverts the behavior.
85 There is a set of standard one-letter command aliases conventional in modern
86 text adventure games; 'l' and 'x'; for 'look' (or 'examine'), 'z' to do nothing
87 for a turn, 'i' for 'inventory', 'g' for 'get', and 'd' for 'drop'. The 'd'
88 alias collides with 'd' for 'down', but the others have been implemented.
89 The "-o" (oldstyle) option disables them.
91 Unrecognized words are no longer truncated to 5 characters and
92 uppercased when they are echoed. The "-o" (oldstyle) option restores
95 A "seed" command has been added. This is not intended for human use
96 but as a way for game logs to set the PRNG (pseudorandom-number generator) so
97 that random events (dwarf & pirate appearances, the bird's magic word)
100 A "version" command has been added. This has no effect on gameplay.
102 The text displayed by the "news" command has been updated.
104 A -l command-line option has been added. When this is given (with a
105 file path argument) each command entered will be logged to the
106 specified file. Additionally, a generated "seed" command will be put
107 early in the file capturing the randomized start state of the PRNG
108 so that replays of the log will be reproducible.
110 Using "seed" and -l, the distribution now includes a regression-test
111 suite for the game. Any log captured with -l (and thus containing
112 a "seed" command) will replay reliably, including random events.
114 The adventure.text file is no longer required at runtime. Instead, an
115 adventure.yaml file is compiled at build time to a source module
116 containing C structures, which is then linked to the advent
117 binary. The YAML is drastically easier to read and edit than
118 the old ad-hoc format of adventure.txt.
120 The game-save format has changed. This was done to simplify the
121 FORTRAN-derived code that formerly implemented the save/restore
122 functions; without C's fread(3)/fwrite() and structs it was
123 necessarily pretty ugly by modern standards. Encryption and
124 checksumming have been discarded - it's pointless to try
125 tamper-proofing saves when everyone has the source code. However
126 the game still integrity-checks savefiles on resume, including an
127 abort if the endianness of the restoring machine does not match that of
128 the saving machine. There is a magic-cookie header on the saves so
129 in theory they could be identified by programs like file(1).
131 Save and resume filenames are stripped of leading and trailing
132 whitespace before processing.
134 A -r command-line option has been added. When it is given (with a file
135 path argument) it is functionally equivalent to a RESTORE command.
137 An -a command-line option has been added (comditionally on
138 ADVENT_AUTOSAVE) for use in BBS door systems. When this option is
139 given, the game roads from the specified filename argument on startup
140 and saves to it on quit or a received signal. There is a new nmessage
141 to inform the user about this.
143 The game can be built in a mode that entirely disables save/resume
144 (-DADVENT_NOSAVE). If the game had been built this way, a diagnostic is
145 emitted if you try to save or resume.
149 The 2.5 code was a mechanical C translation of a FORTRAN original.
150 There were gotos everywhere and the code was, though functional,
151 ugly and quite unreadable.
153 Jason Ninneman and I have moved it to what is almost, but not quite,
154 idiomatic modern C. We refactored the right way, checking correctness
155 against a comprehensive test suite that we built first and verified
156 with coverage tools (there is effectively 100% code coverage). This is
157 what you are running when you do "make check".
159 The move to modern C entailed some structural changes. The most
160 important was the refactoring of over 350 gotos into if/loop/break
161 structures. We also abolished almost all shared globals; the main one
162 left is a struct holding the game's saveable/restorable state.
164 The original code was greatly complicated by a kind of bit-packing
165 that was performed because the FORTRAN it was written in had no string
166 type. Text from the adventure.text file was compiled into sequences
167 of sixbit code points in a restricted character set, packed 5 to a
168 32-bit word (and it seems clear from the code that words were originally
169 *6* chars each packed into a PDP-10 36-bit word). A command noun or
170 verb was one of these words, and what would be string operations in a
171 more recent language were all done on sequences of these words.
173 We have removed all this bit-packing cruft in favor of proper C
174 strings. C strings may be a weak and leaky abstraction, but this is
175 one of the rare cases in which they are an obvious improvement over
176 what they're displacing...
178 We have also conducted extensive fuzz testing on the game using
179 afl (American Fuzzy Lop). We've found and fixed some crashers in
180 our new code (which occasionally uses malloc(3)), but none as yet
181 in Don's old code (which didn't).
183 After version 1.11, correctness was carefully checked against the
184 behavior of a binary from before the big refactoring.
186 The code falls short of being fully modern C in the following
189 * We have not attempted to translate the old code to pointer-based
190 idioms (as opposed, in particular, to integer-based array indexing).
191 We don't need whatever minor performance gains this might collect,
192 and the choice to refrain will make forward translation into future
195 * Linked lists (for objects at a location) are implemented using an array
196 of link indices. This is a surviving FORTRANism that is quite unlike
197 normal practice in C or any more modern language. We have not tried
198 to fix it because doing so would (a) be quite difficult, and (b)
199 compromise forward-portability to other languages.
201 * Much of the code still assumes one-origin array indexing. Thus,
202 arrays are a cell larger than they strictly need to be and cell 0 is
205 We have made exactly one minor architectural change. In addition to the
206 old code's per-object state-description messages, we now have a per-object
207 message series for state *changes*. This makes it possible to pull a fair
208 amount of text out of the arbitrary-messages list and associate those
209 messages with the objects that conceptually own them.
211 == Development status ==
213 We consider this project finished. All issues and TODOs have been
214 cleared, behavior has been carefully checked against original ADVENT,
215 no future demand for new features is expected, and the test suite has
216 100% code coverage. If new bugs appear the toolchain bit-rots out
217 from under underneath, we will fix those problems.