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68 lines
2 KiB
Markdown
68 lines
2 KiB
Markdown
# xxhash
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[](https://godoc.org/github.com/cespare/xxhash)
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[](https://travis-ci.org/cespare/xxhash)
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xxhash is a Go implementation of the 64-bit
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[xxHash](http://cyan4973.github.io/xxHash/) algorithm, XXH64. This is a
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high-quality hashing algorithm that is much faster than anything in the Go
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standard library.
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This package provides a straightforward API:
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```
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func Sum64(b []byte) uint64
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func Sum64String(s string) uint64
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type Digest struct{ ... }
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func New() *Digest
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```
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The `Digest` type implements hash.Hash64. Its key methods are:
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```
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func (*Digest) Write([]byte) (int, error)
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func (*Digest) WriteString(string) (int, error)
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func (*Digest) Sum64() uint64
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```
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This implementation provides a fast pure-Go implementation and an even faster
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assembly implementation for amd64.
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## Compatibility
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This package is in a module and the latest code is in version 2 of the module.
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You need a version of Go with at least "minimal module compatibility" to use
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github.com/cespare/xxhash/v2:
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* 1.9.7+ for Go 1.9
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* 1.10.3+ for Go 1.10
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* Go 1.11 or later
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I recommend using the latest release of Go.
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## Benchmarks
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Here are some quick benchmarks comparing the pure-Go and assembly
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implementations of Sum64.
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| input size | purego | asm |
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| --- | --- | --- |
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| 5 B | 979.66 MB/s | 1291.17 MB/s |
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| 100 B | 7475.26 MB/s | 7973.40 MB/s |
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| 4 KB | 17573.46 MB/s | 17602.65 MB/s |
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| 10 MB | 17131.46 MB/s | 17142.16 MB/s |
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These numbers were generated on Ubuntu 18.04 with an Intel i7-8700K CPU using
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the following commands under Go 1.11.2:
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```
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$ go test -tags purego -benchtime 10s -bench '/xxhash,direct,bytes'
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$ go test -benchtime 10s -bench '/xxhash,direct,bytes'
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```
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## Projects using this package
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- [InfluxDB](https://github.com/influxdata/influxdb)
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- [Prometheus](https://github.com/prometheus/prometheus)
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- [FreeCache](https://github.com/coocood/freecache)
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