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62 lines
1.9 KiB
Markdown
62 lines
1.9 KiB
Markdown
# Jump Consistent Hash
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[](https://travis-ci.org/lithammer/go-jump-consistent-hash)
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[](https://godoc.org/github.com/lithammer/go-jump-consistent-hash)
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Go implementation of the jump consistent hash algorithm[1] by John Lamping and Eric Veach.
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[1] http://arxiv.org/pdf/1406.2294v1.pdf
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## Usage
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```go
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import jump "github.com/lithammer/go-jump-consistent-hash"
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func main() {
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h := jump.Hash(256, 1024) // h = 520
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}
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```
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Includes a helper function for using a `string` as key instead of an `uint64`. This requires a hasher that computes the string into a format accepted by `Hash()`. Such a hasher that uses [CRC-64 (ECMA)](https://en.wikipedia.org/wiki/Cyclic_redundancy_check) is also included for convenience.
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```go
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h := jump.HashString("127.0.0.1", 8, jump.NewCRC64()) // h = 7
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```
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In reality though you probably want to use a `Hasher` so you won't have to repeat the bucket size and which key hasher used. It also uses more convenient types, like `int` instead of `int32`.
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```go
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hasher := jump.New(8, jump.NewCRC64())
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h := hasher.Hash("127.0.0.1") // h = 7
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```
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If you want to use your own algorithm, you must implement the `KeyHasher` interface, which is a subset of the `hash.Hash64` interface available in the standard library.
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Here's an example of a custom `KeyHasher` that uses Google's [FarmHash](https://github.com/google/farmhash) algorithm (the successor of CityHash) to compute the final key.
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```go
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type FarmHash struct {
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buf bytes.Buffer
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}
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func (f *FarmHash) Write(p []byte) (n int, err error) {
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return f.buf.Write(p)
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}
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func (f *FarmHash) Reset() {
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f.buf.Reset()
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}
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func (f *FarmHash) Sum64() uint64 {
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// https://github.com/dgryski/go-farm
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return farm.Hash64(f.buf.Bytes())
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}
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hasher := jump.New(8, &FarmHash{})
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h := hasher.Hash("127.0.0.1") // h = 5
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```
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## License
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MIT
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