encoding/binary: fix error message
In the process, simplified internal sizeOf and
dataSize functions. Minor positive impact on
performance. Added test case.
benchmark old ns/op new ns/op delta
BenchmarkReadSlice1000Int32s 14006 14122 +0.83%
BenchmarkReadStruct 2508 2447 -2.43%
BenchmarkReadInts 921 928 +0.76%
BenchmarkWriteInts 2086 2081 -0.24%
BenchmarkWriteSlice1000Int32s 13440 13497 +0.42%
BenchmarkPutUvarint32 28.5 26.3 -7.72%
BenchmarkPutUvarint64 81.3 76.7 -5.66%
benchmark old MB/s new MB/s speedup
BenchmarkReadSlice1000Int32s 285.58 283.24 0.99x
BenchmarkReadStruct 27.90 28.60 1.03x
BenchmarkReadInts 32.57 32.31 0.99x
BenchmarkWriteInts 14.38 14.41 1.00x
BenchmarkWriteSlice1000Int32s 297.60 296.36 1.00x
BenchmarkPutUvarint32 140.55 151.92 1.08x
BenchmarkPutUvarint64 98.36 104.33 1.06x
Fixes #6818.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/
149290045