alt Hacker NewsYeah the raw parse speed comparison is almost a red herring at this point. The real cost with JSON is when you have a 200MB manifest or build artifact and you need exactly two fields out of it. You're still loading the whole thing into memory, building the full object graph, and GC gets to clean all of it up after. That's the part where something like RX with selective access actually matters. Parse speed benchmarks don't capture that at all.
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as parser: keep only indexes to the original file (input), dont copy strings or parse numbers at all (unless the strings fit in the index width, e.g. 32bit)
That would make parsing faster and there will be very little in terms on tree (json can't really contain full blow graphs) but it's rather complicated, and it will require hashing to allow navigation, though.
> The real cost with JSON is when you have a 200MB manifest or build artifact and you need exactly two fields out of it.
There are SAX-like JSON libraries out there, and several of them work with a preallocated buffer or similar streaming interface, so you could stream the file and pick out the two fields as they come along.