Turn DataBuffer into an interface, have an impl that takes a String

[slandelle]

I've tried to optimize things (smaller inlinable methods, switches instead of if/elseif, cached parser instances).

So far, the only thing that did performed better was turning DataCharBuffer into an interface, and add an implementation that wraps a String instead of a char array, thus saving an array copy.

This improved performance on big JSON messages of ~15%.

I'm still puzzled about your implementation being beaten by gson and json-smart on smaller messages. I suspect IndexBuffer's arrays allocation.

[jjenkov]

That could actually be a reason - because an IndexBuffer allocates 3 arrays internally. With 2 IndexBuffers in use, that means 8 objects allocated (2 x IndexBuffer + 6 arrays). That might be a big overhead on small JSON strings.

There is another small performance optimization that can be done. I think the parseNumberToken() method starts scanning from the first character in the number. But we already know that the first character is a number character, otherwise parseNumberToken() would not have been called. That means that tokenLength could be initialized to 1 instead of 0 inside parseNumberToken, thus saving 1 character comparison per number (unless I am mistaken). It's not a lot, but if you want to fine tune the parser, all stones must be turned :-)

[jjenkov]

Just added the tokenLength optimization in the parseNumber() method. I will play around with a few other optimizations this weekend.

[slandelle]

Yeah, I already added that one on my copy.

I realized that my test on my biggest sample was flawed because your parser doesn't support booleans for now.
I think having growable arrays will mostly improve performance for big json payloads.

Still not sure about why performance for small ones is not that good.

[jjenkov]

I've got support for booleans added now.

[jjenkov]

I've got several performance optimizations into the code now. I have also implemented a JsonParser2 which merges the tokenization and parsing phase into a single phase and class. That is 25% faster than when the two phases are split in two. The JsonParser2 beats GSON streaming by a factor 2,5 to 5 depending on the file size (smaller files are faster).