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