commit a11fcdc3c6a0480f74404d4485ebf68c4e23fb0c
author Todd Wang <toddw@google.com> Mon Nov 16 15:00:29 2015 -0800
committer Todd Wang <toddw@google.com> Mon Nov 16 15:00:29 2015 -0800
tree 5f1088c71c33e39966aea73a9ebe9501d46353c1
parent b9f9d6d0f07ca69a5e68613a8fe2c9ae3b1af905

textutil: Simplify and speedup RuneChunkDecoder, add linewrap.

[NOTE: nobody actually uses the RuneChunkDecoder API; it's only
used in the LineWriter in the same package]

The old RuneChunkDecoder API was unnecessarily complicated and
slow.  In general returning an interface from an interface method
is bad for operations that are called many times, since the
returned interface is always represented by a pointer (in Go
1.4+), which commonly means that an allocation must be performed.

Added some benchmarks to show the difference.  In this case we
don't really care about the performance, but it's nice to get a
simpler API as well.

Also added a simple tool "linewrap", which formats text from
stdin into pretty output on stdout, using LineWriter.

ns/op                                    old     new   delta
UTF8LineWriter_Sizes_0_Width_0        948244  933565  -1.55%
UTF8LineWriter_Sizes_0_Width_10      1002200  980595  -2.16%
UTF8LineWriter_Sizes_0_Width_Inf      882431  861149  -2.41%
UTF8LineWriter_Sizes_1_Width_0       2327690 1341671 -42.36%
UTF8LineWriter_Sizes_1_Width_10      2369511 1397329 -41.03%
UTF8LineWriter_Sizes_1_Width_Inf     2248815 1275818 -43.27%
UTF8LineWriter_Sizes_1_2_3_Width_0   1717722 1206084 -29.79%
UTF8LineWriter_Sizes_1_2_3_Width_10  1765252 1251204 -29.12%
UTF8LineWriter_Sizes_1_2_3_Width_Inf 1641235 1123916 -31.52%
UTF8ChunkDecoder_Sizes_0              219613  189368 -13.77%
UTF8ChunkDecoder_Sizes_1             1428130  552981 -61.28%
UTF8ChunkDecoder_Sizes_1_2_3          869106  389633 -55.17%

allocs                                 old new   delta
UTF8LineWriter_Sizes_0_Width_0          15  13 -13.33%
UTF8LineWriter_Sizes_0_Width_10         15  13 -13.33%
UTF8LineWriter_Sizes_0_Width_Inf        17  15 -11.76%
UTF8LineWriter_Sizes_1_Width_0       13314  13 -99.90%
UTF8LineWriter_Sizes_1_Width_10      13314  13 -99.90%
UTF8LineWriter_Sizes_1_Width_Inf     13316  15 -99.89%
UTF8LineWriter_Sizes_1_2_3_Width_0    6665  13 -99.80%
UTF8LineWriter_Sizes_1_2_3_Width_10   6665  13 -99.80%
UTF8LineWriter_Sizes_1_2_3_Width_Inf  6667  15 -99.78%
UTF8ChunkDecoder_Sizes_0                23  21  -8.70%
UTF8ChunkDecoder_Sizes_1             13322  21 -99.84%
UTF8ChunkDecoder_Sizes_1_2_3          6673  21 -99.69%

Change-Id: Ifd649cb884a23397ec54332827aff9b8f457d1d2