README.md
1# xxhash [](https://godoc.org/github.com/OneOfOne/xxhash) [](https://travis-ci.org/OneOfOne/xxhash) [](https://gocover.io/github.com/OneOfOne/xxhash)
2
3This 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.
4
5* The C implementation is ([Copyright](https://github.com/Cyan4973/xxHash/blob/master/LICENSE) (c) 2012-2014, Yann Collet)
6
7## Install
8
9 go get github.com/OneOfOne/xxhash
10
11## Features
12
13* On Go 1.7+ the pure go version is faster than CGO for all inputs.
14* Supports ChecksumString{32,64} xxhash{32,64}.WriteString, which uses no copies when it can, falls back to copy on appengine.
15* The native version falls back to a less optimized version on appengine due to the lack of unsafe.
16* Almost as fast as the mostly pure assembly version written by the brilliant [cespare](https://github.com/cespare/xxhash), while also supporting seeds.
17* To manually toggle the appengine version build with `-tags safe`.
18
19## Benchmark
20
21### Core i7-4790 @ 3.60GHz, Linux 4.12.6-1-ARCH (64bit), Go tip (+ff90f4af66 2017-08-19)
22
23```bash
24➤ go test -bench '64' -count 5 -tags cespare | benchstat /dev/stdin
25name time/op
26
27# https://github.com/cespare/xxhash
28XXSum64Cespare/Func-8 160ns ± 2%
29XXSum64Cespare/Struct-8 173ns ± 1%
30XXSum64ShortCespare/Func-8 6.78ns ± 1%
31XXSum64ShortCespare/Struct-8 19.6ns ± 2%
32
33# this package (default mode, using unsafe)
34XXSum64/Func-8 170ns ± 1%
35XXSum64/Struct-8 182ns ± 1%
36XXSum64Short/Func-8 13.5ns ± 3%
37XXSum64Short/Struct-8 20.4ns ± 0%
38
39# this package (appengine, *not* using unsafe)
40XXSum64/Func-8 241ns ± 5%
41XXSum64/Struct-8 243ns ± 6%
42XXSum64Short/Func-8 15.2ns ± 2%
43XXSum64Short/Struct-8 23.7ns ± 5%
44
45CRC64ISO-8 1.23µs ± 1%
46CRC64ISOString-8 2.71µs ± 4%
47CRC64ISOShort-8 22.2ns ± 3%
48
49Fnv64-8 2.34µs ± 1%
50Fnv64Short-8 74.7ns ± 8%
51#
52```
53
54## Usage
55
56```go
57 h := xxhash.New64()
58 // r, err := os.Open("......")
59 // defer f.Close()
60 r := strings.NewReader(F)
61 io.Copy(h, r)
62 fmt.Println("xxhash.Backend:", xxhash.Backend)
63 fmt.Println("File checksum:", h.Sum64())
64```
65
66[<kbd>playground</kbd>](http://play.golang.org/p/rhRN3RdQyd)
67
68## TODO
69
70* Rewrite the 32bit version to be more optimized.
71* General cleanup as the Go inliner gets smarter.
72
73## License
74
75This project is released under the Apache v2. licence. See [LICENCE](LICENCE) for more details.
76
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