# xxhash [![GoDoc](https://godoc.org/github.com/OneOfOne/xxhash?status.svg)](https://godoc.org/github.com/OneOfOne/xxhash) [![Build Status](https://travis-ci.org/OneOfOne/xxhash.svg?branch=master)](https://travis-ci.org/OneOfOne/xxhash) [![Coverage](https://gocover.io/_badge/github.com/OneOfOne/xxhash)](https://gocover.io/github.com/OneOfOne/xxhash)
This is a native Go implementation of the excellent [xxhash](https://github.com/Cyan4973/xxHash)* algorithm, an extremely fast non-cryptographic Hash algorithm, working at speeds close to RAM limits.
* The C implementation is ([Copyright](https://github.com/Cyan4973/xxHash/blob/master/LICENSE) (c) 2012-2014, Yann Collet)
## Install
go get github.com/OneOfOne/xxhash
## Features
* On Go 1.7+ the pure go version is faster than CGO for all inputs.
* Supports ChecksumString{32,64} xxhash{32,64}.WriteString, which uses no copies when it can, falls back to copy on appengine.
* The native version falls back to a less optimized version on appengine due to the lack of unsafe.
* Almost as fast as the mostly pure assembly version written by the brilliant [cespare](https://github.com/cespare/xxhash), while also supporting seeds.
* To manually toggle the appengine version build with `-tags safe`.
## Benchmark
### Core i7-4790 @ 3.60GHz, Linux 4.12.6-1-ARCH (64bit), Go tip (+ff90f4af66 2017-08-19)
```bash
➤ go test -bench '64' -count 5 -tags cespare | benchstat /dev/stdin
name time/op
# https://github.com/cespare/xxhash
XXSum64Cespare/Func-8 160ns ± 2%
XXSum64Cespare/Struct-8 173ns ± 1%
XXSum64ShortCespare/Func-8 6.78ns ± 1%
XXSum64ShortCespare/Struct-8 19.6ns ± 2%
# this package (default mode, using unsafe)
XXSum64/Func-8 170ns ± 1%
XXSum64/Struct-8 182ns ± 1%
XXSum64Short/Func-8 13.5ns ± 3%
XXSum64Short/Struct-8 20.4ns ± 0%
# this package (appengine, *not* using unsafe)
XXSum64/Func-8 241ns ± 5%
XXSum64/Struct-8 243ns ± 6%
XXSum64Short/Func-8 15.2ns ± 2%
XXSum64Short/Struct-8 23.7ns ± 5%
CRC64ISO-8 1.23µs ± 1%
CRC64ISOString-8 2.71µs ± 4%
CRC64ISOShort-8 22.2ns ± 3%
Fnv64-8 2.34µs ± 1%
Fnv64Short-8 74.7ns ± 8%
```
## Usage
```go
h := xxhash.New64()
// r, err := os.Open("......")
// defer f.Close()
r := strings.NewReader(F)
io.Copy(h, r)
fmt.Println("xxhash.Backend:", xxhash.Backend)
fmt.Println("File checksum:", h.Sum64())
```
[<kbd>playground</kbd>](https://play.golang.org/p/wHKBwfu6CPV)
## TODO
* Rewrite the 32bit version to be more optimized.
* General cleanup as the Go inliner gets smarter.
## License
This project is released under the Apache v2. license. See [LICENSE](LICENSE) for more details.