region: Simplify buffer funcs

[aaronbee]

Replace growBuffer with append and resizeBufferCap with slices.Grow. And remove redundant if checks on capacity or size that append will do as well. This is equivalent behavior after undoing the unintentional change from commit 1fee39f. Benchmarks show the performance is equivalent to the code before commit 1fee39f.

Also replace some deprecated calls to rand funcs.

[dethi]

LGTM, but QQ: how do you know the change to resizeBufferCap was unintentional?

[aaronbee]

LGTM, but QQ: how do you know the change to resizeBufferCap was unintentional?

I spoke to @tsuna about it. He has no recollection of making that change and didn't mean to submit it with the other unrelated changes in #255.

It causeed a slow down because an append was replaced with a make to create a slice. make doesn't leave any slack at the end of the slice so it's more likely to need to be reallocated:

goos: darwin
goarch: amd64
pkg: github.com/tsuna/gohbase/region
cpu: Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
                                        │ existing.txt │             before.txt              │
                                        │    sec/op    │   sec/op     vs base                │
DecompressCellblocks1/BlockLen10-16        71.08n ± 0%   60.99n ± 0%  -14.20% (p=0.000 n=10)
DecompressCellblocks1/BlockLen100-16       254.3n ± 0%   243.9n ± 1%   -4.07% (p=0.000 n=10)
DecompressCellblocks1/BlockLen1000-16      1.986µ ± 0%   1.961µ ± 0%   -1.21% (p=0.000 n=10)
DecompressCellblocks1/BlockLen10000-16     18.86µ ± 0%   18.81µ ± 0%   -0.24% (p=0.002 n=10)
DecompressCellblocks10/BlockLen10-16       468.3n ± 0%   740.8n ± 0%  +58.18% (p=0.000 n=10)
DecompressCellblocks10/BlockLen100-16      2.811µ ± 1%   3.603µ ± 0%  +28.20% (p=0.000 n=10)
DecompressCellblocks10/BlockLen1000-16     26.17µ ± 1%   29.50µ ± 0%  +12.75% (p=0.000 n=10)
DecompressCellblocks10/BlockLen10000-16    249.3µ ± 1%   268.3µ ± 0%   +7.62% (p=0.000 n=10)
geomean                                    2.955µ        3.221µ        +9.02%

                                        │ existing.txt │               before.txt                │
                                        │     B/op     │     B/op      vs base                   │
DecompressCellblocks1/BlockLen10-16         16.00 ± 0%     16.00 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen100-16        112.0 ± 0%     112.0 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen1000-16     1.000Ki ± 0%   1.000Ki ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen10000-16    10.00Ki ± 0%   10.00Ki ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks10/BlockLen10-16        240.0 ± 0%     616.0 ± 0%  +156.67% (p=0.000 n=10)
DecompressCellblocks10/BlockLen100-16     2.641Ki ± 0%   5.719Ki ± 0%  +116.57% (p=0.000 n=10)
DecompressCellblocks10/BlockLen1000-16    40.25Ki ± 0%   56.50Ki ± 0%   +40.37% (p=0.000 n=10)
DecompressCellblocks10/BlockLen10000-16   423.3Ki ± 0%   566.0Ki ± 0%   +33.73% (p=0.000 n=10)
geomean                                   1.914Ki        2.566Ki        +34.06%
¹ all samples are equal

                                        │ existing.txt │               before.txt               │
                                        │  allocs/op   │  allocs/op   vs base                   │
DecompressCellblocks1/BlockLen10-16         1.000 ± 0%    1.000 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen100-16        1.000 ± 0%    1.000 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen1000-16       1.000 ± 0%    1.000 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks1/BlockLen10000-16      1.000 ± 0%    1.000 ± 0%         ~ (p=1.000 n=10) ¹
DecompressCellblocks10/BlockLen10-16        4.000 ± 0%   10.000 ± 0%  +150.00% (p=0.000 n=10)
DecompressCellblocks10/BlockLen100-16       5.000 ± 0%   10.000 ± 0%  +100.00% (p=0.000 n=10)
DecompressCellblocks10/BlockLen1000-16      7.000 ± 0%   10.000 ± 0%   +42.86% (p=0.000 n=10)
DecompressCellblocks10/BlockLen10000-16     7.000 ± 0%   10.000 ± 0%   +42.86% (p=0.000 n=10)
geomean                                     2.365         3.162        +33.69%
¹ all samples are equal

This PR restores the previous performance.

[tsuna]

Thanks for fixing my mistake, I'm not sure how I managed to get that change in, when all I meant to do was to add a metric.