archive/tar: reuse temporary buffer in readHeader
A temporary 512 bytes buffer is allocated for every call to
readHeader. This buffer isn't returned to the caller and it could
be reused to lower the number of memory allocations.
This CL improves it by using a pool and zeroing out the buffer before
putting it back into the pool.
benchmark old ns/op new ns/op delta
BenchmarkListFiles100k
545249903 538832687 -1.18%
benchmark old allocs new allocs delta
BenchmarkListFiles100k
2105167 2005692 -4.73%
benchmark old bytes new bytes delta
BenchmarkListFiles100k
105903472 54831527 -48.22%
This improvement is very important if your code has to deal with a lot
of tarballs which contain a lot of files.
LGTM=dsymonds
R=golang-codereviews, dave, dsymonds, bradfitz
CC=golang-codereviews
https://golang.org/cl/
108240044