Split fields without regular expressions

[djc]

No description provided.

[197g]

https://gist.github.com/HeroicKatora/9d3e4c179e2460e550b65630903d2674

Here are some ideas for speeding up field selection, in particular when only few fields are requested. Execute the benchmarks, hope they are as convincing on your machine as on mine.

test bench_char        ... bench:         124 ns/iter (+/- 4)
test bench_char_few    ... bench:          96 ns/iter (+/- 7)
test bench_indexed     ... bench:         101 ns/iter (+/- 4)
test bench_indexed_few ... bench:           5 ns/iter (+/- 0)
test bench_split       ... bench:         120 ns/iter (+/- 3)
test bench_split_few   ... bench:          87 ns/iter (+/- 3)

[djc]

@HeroicKatora thanks, I'll see if that helps at the macro level.

[197g]

I would test integrating them but I don't have anything to execute the benchmarks against. I'm just a bit annoyed that the Go version is faster, no other personal use :)

[djc]

I integrated your changes -- I found some issues which I corrected enough to make the tests pass (see the commit I pushed). However, it looks like the performance is still a wash against current master.