Jomini
A low level, performance oriented parser for EU4 save files and other PDS developed titles. Consult the write-up for an in-depth look at the Paradox Clausewitz format and the pitfalls that come trying to support all variations. It's extremely difficult to write a robust and fast parser for this format, but jomini accomplishes both tasks.
Jomini is the cornerstone of Rakaly, an EU4 achievement leaderboard and save file analyzer. This library is also powers the Paradox Game Converters and pdxu to parse ironman EU4, CK3, HOI4, and Imperator saves.
Features
- ✔ Versatile: Handle both plaintext and binary encoded data
- ✔ Fast: Parse data at over 1 GB/s
- ✔ Small: Compile with zero dependencies
- ✔ Safe: Extensively fuzzed against potential malicious input
- ✔ Ergonomic: Use serde-like macros to have parsing logic automatically implemented
- ✔ Embeddable: Cross platform native apps, statically compiled services, or in the browser via WASM
- ✔ Agnostic: Parse EU4, HOI4, Imperator, CK3, and Vic2 save and game files
Quick Start
Below is a demonstration on parsing plaintext data using jomini tools.
use ;
let data = br#"
human = yes
forth = 10
core = "HAB"
names = { "Johan" "Frederick" }
core = FRA
"#;
let expected = Model ;
let actual: Model = from_windows1252_slice?;
assert_eq!;
Binary Parsing
Parsing data encoded in the binary format is done in a similar fashion but with an extra step. Tokens can be encoded into 16 integers, and so one must provide a map from these integers to their textual representations
use ;
use HashMap;
let data = ;
let mut map = new;
map.insert;
let actual: MyStruct = from_eu4?;
assert_eq!;
When done correctly, one can use the same structure to represent both the plaintext and binary data without any duplication.
One can configure the behavior when a token is unknown (ie: fail immediately or try to continue).
Caveats
Caller is responsible for:
- Determining the correct format (text or binary) ahead of time
- Stripping off any header that may be present (eg:
EU4txt
/EU4bin
) - Providing the token resolver for the binary format
- Providing the conversion to reconcile how, for example, a date may be encoded as an integer in the binary format, but as a string when in plaintext.
The Mid-level API
If the automatic deserialization via JominiDeserialize
is too high level, there is a mid-level
api where one can easily iterate through the parsed document and interrogate fields for
their information.
use TextTape;
let data = b"name=aaa name=bbb core=123 name=ccc name=ddd";
let tape = from_slice.unwrap;
let mut reader = tape.windows1252_reader;
while let Some = reader.next_field
One Level Lower
At the lowest layer, one can interact with the raw data directly via TextTape
and BinaryTape
.
use ;
let data = b"foo=bar";
assert_eq!;
If one will only use TextTape
and BinaryTape
then jomini
can be compiled without default
features, resulting in a build without dependencies.
Write API
There are two targeted use cases for the write API. One is when a text tape is on hand. This is useful when one needs to reformat a document (note that comments are not preserved):
use ;
let tape = from_slice?;
let mut out: = Vec new;
let mut writer = new.from_writer;
writer.write_tape?;
assert_eq!;
The writer normalizes any formatting issues. The writer is not able to losslessly write all parsed documents, but these are limited to truly esoteric situations and hope to be resolved in future releases.
The other use case is geared more towards incremental writing that can be found in melters or those crafting documents by hand. These use cases need to manually drive the writer:
use TextWriterBuilder;
let mut out: = Vec new;
let mut writer = new.from_writer;
writer.write_unquoted?;
writer.write_unquoted?;
writer.write_unquoted?;
writer.write_unquoted?;
assert_eq!;
Unsupported Syntax
Due to the nature of Clausewitz being closed source, this library can never guarantee compatibility with Clausewitz. There is no specification of what valid input looks like, and we only have examples that have been collected in the wild. From what we do know, Clausewitz is recklessly flexible: allowing each game object to potentially define its own unique syntax. It is technically possible for us to support these fringe edge cases in search for perfection, but achieving that goal would sacrifice either ergonomics or performance: two pillars that are a must for save game parsing. Until a suitable solution is presented, a workaround would be to preprocess the unique syntax into a more recognizable format.
The good news is that unsupported syntax is typically isolated in a handful of game files.
Known unsupported syntax:
-
simple_cross_flag = { pattern = list "christian_emblems_list" color1 = list "normal_colors" }
Above is an example of an unmarked list found in CK3. Typically lists are use brackets (
{
,}
) but those are conspicuously missing here. -
on_actions = { faith_holy_order_land_acquisition_pulse delay = { days = { 5 10 }} faith_heresy_events_pulse delay = { days = { 15 20 }} faith_fervor_events_pulse }
Alternating value and key value pairs. Makes one wish they used a bit more of a self describing format. We can parse objects or lists that occur at the end of a container, but are unable to repeatedly switch between the two formats.
-
pride_of_the_fleet = yes definition definition = heavy_cruiser
In this instance, the first
definition
should be skipped, but skipping an unrecognized or duplicate field is not consistent across game objects, as we can see from the previous examples where one shouldn't skip fields like this.
Benchmarks
Benchmarks are ran with the following command:
cargo clean
cargo bench -- '/ck3'
find ./target -wholename "*/new/raw.csv" -print0 | xargs -0 xsv cat rows > assets/jomini-benchmarks.csv
And can be analyzed with the R script found in the assets directory.
Below is a graph generated from benchmarking on an arbitrary computer.