jonason is just a practice project to mess around with optimizing in C++. I named it jonason because it kinda sounds like JSON and kinda sounds like a name (and the Jason pun has been overused at this point).
Far from compliant, but it can still parse some basic JSON.
Known limitations:
- Error handling is awful, you either get "Unexpected EOF" or "Unexpected token"
- Invalid number literals are just parsed as 0 and overflows are not handled
- An empty array with commas is parsed just fine (should be invalid)
- Probably doesn't support many encodings well
Learnings:
- I started with value semantics for
JSONValuebut quickly switched to pointers when the benchmark was calling the copy-assignment operator millions of times - Messing around with anonymous unions was "interesting" but made copy-constructor and copy-assignment operator pretty annoying to implement
- Always run tests with address sanitizer on
- Just use
std::unique_ptr - Using
std::istream::getto skip whitespaces was surprisingly slow compared tostd::ws
What I'd like to improve if I could lock myself in a cave and code for a week:
- Merge the tokenize and parse steps to reduce the overhead
- Use
JSON_checkerto test conformance to specification
Parsing performance results
- clang-1400.0.29.202
- 2.9 GHz 6-Core Intel Core i9
| input | jonason | NSJSONSerialization |
|---|---|---|
| canada.json | ~105 ms | ~75 ms |
| citm_ca.json | ~21 ms | ~10 ms |
Unfortunately, jonsason is not only unreliable, but also abit slow. Regardless, I'm pretty happy with the results.