jonason, your friendly yet unreliable JSON parser

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 JSONValue but 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::get to skip whitespaces was surprisingly slow compared to std::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_checker to 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.