Replace classOf with a lookup table.

Improve performance of byte classification using a static lookup table.  The
improvement over a function is not as great as the gain from using a function
over a map, but it's enough to be worthwhile.

```
BENCHMARK                      BEFORE    AFTER    SPEEDUP (%)
BenchmarkSplit/len_1-12        570       563      1.2
BenchmarkSplit/len_4-12        612       600      2.0
BenchmarkSplit/len_16-12       714       704      1.4
BenchmarkSplit/len_64-12       1119      1082     3.3
BenchmarkSplit/len_256-12      2965      2799     5.6
BenchmarkSplit/len_1024-12     10216     8928     12.6
BenchmarkSplit/len_4096-12     39333     33102    15.8
BenchmarkSplit/len_16384-12    158126    130540   17.4
BenchmarkSplit/len_65536-12    669554    566011   15.5
BenchmarkSplit/len_100739-12   1039795   884622   14.9
```
1 file changed
tree: ef2af7c16684f7c30ab43633496605cccbfec960
  1. bench_test.go
  2. bitbucket-pipelines.yml
  3. go.mod
  4. LICENSE
  5. README.md
  6. shell.go
  7. shell_test.go
README.md

shell

http://godoc.org/bitbucket.org/creachadair/shell

The shell package implements basic shell command-line splitting.