spaolacci
implement io.StringWriter
Hello!
This PR adds a WriteString method to the internal digest type to implement the io.StringWriter interface and avoid memory copies when hashing strings.
I added a benchmark and ran it before and after the change to demonstrate that a heap allocation is removed by providing this method:
benchmark old ns/op new ns/op delta
BenchmarkWriteString/1 46.0 30.8 -33.04%
BenchmarkWriteString/2 46.1 31.8 -31.02%
BenchmarkWriteString/4 43.5 28.4 -34.71%
BenchmarkWriteString/8 42.1 28.9 -31.35%
BenchmarkWriteString/16 48.3 31.3 -35.20%
BenchmarkWriteString/32 54.2 34.9 -35.61%
benchmark old MB/s new MB/s speedup
BenchmarkWriteString/1 21.75 32.46 1.49x
BenchmarkWriteString/2 43.43 62.89 1.45x
BenchmarkWriteString/4 92.01 140.65 1.53x
BenchmarkWriteString/8 190.10 277.23 1.46x
BenchmarkWriteString/16 331.10 510.92 1.54x
BenchmarkWriteString/32 590.65 916.96 1.55x
benchmark old allocs new allocs delta
BenchmarkWriteString/1 1 0 -100.00%
BenchmarkWriteString/2 1 0 -100.00%
BenchmarkWriteString/4 1 0 -100.00%
BenchmarkWriteString/8 1 0 -100.00%
BenchmarkWriteString/16 1 0 -100.00%
BenchmarkWriteString/32 1 0 -100.00%
benchmark old bytes new bytes delta
BenchmarkWriteString/1 8 0 -100.00%
BenchmarkWriteString/2 8 0 -100.00%
BenchmarkWriteString/4 8 0 -100.00%
BenchmarkWriteString/8 8 0 -100.00%
BenchmarkWriteString/16 16 0 -100.00%
BenchmarkWriteString/32 32 0 -100.00%
The use of the unsafe package is a bit unfortunate, but it seemed like the package already depended on it, so this change doesn't introduce a new dependency on unsafe.
Let me know if you'd like to see anything changed!
Hello @twmb, would you like to get this PR merged or would you prefer not to bring it in?
I'm not a gate on this repo, I just saw the PR and decided to look since I fixed roughly the same thing in my own fork from way back.
We're maintaining a fork as well which includes this optimization https://github.com/segmentio/murmur3 (in case it is useful to someone).