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76 lines
2.2 KiB
Markdown
76 lines
2.2 KiB
Markdown
# hashstructure [](https://godoc.org/github.com/mitchellh/hashstructure)
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hashstructure is a Go library for creating a unique hash value
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for arbitrary values in Go.
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This can be used to key values in a hash (for use in a map, set, etc.)
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that are complex. The most common use case is comparing two values without
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sending data across the network, caching values locally (de-dup), and so on.
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## Features
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* Hash any arbitrary Go value, including complex types.
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* Tag a struct field to ignore it and not affect the hash value.
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* Tag a slice type struct field to treat it as a set where ordering
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doesn't affect the hash code but the field itself is still taken into
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account to create the hash value.
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* Optionally, specify a custom hash function to optimize for speed, collision
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avoidance for your data set, etc.
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* Optionally, hash the output of `.String()` on structs that implement fmt.Stringer,
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allowing effective hashing of time.Time
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* Optionally, override the hashing process by implementing `Hashable`.
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## Installation
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Standard `go get`:
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```
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$ go get github.com/mitchellh/hashstructure/v2
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```
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**Note on v2:** It is highly recommended you use the "v2" release since this
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fixes some significant hash collisions issues from v1. In practice, we used
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v1 for many years in real projects at HashiCorp and never had issues, but it
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is highly dependent on the shape of the data you're hashing and how you use
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those hashes.
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When using v2+, you can still generate weaker v1 hashes by using the
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`FormatV1` format when calling `Hash`.
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## Usage & Example
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For usage and examples see the [Godoc](http://godoc.org/github.com/mitchellh/hashstructure).
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A quick code example is shown below:
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```go
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type ComplexStruct struct {
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Name string
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Age uint
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Metadata map[string]interface{}
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}
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v := ComplexStruct{
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Name: "mitchellh",
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Age: 64,
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Metadata: map[string]interface{}{
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"car": true,
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"location": "California",
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"siblings": []string{"Bob", "John"},
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},
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}
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hash, err := hashstructure.Hash(v, hashstructure.FormatV2, nil)
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if err != nil {
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panic(err)
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}
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fmt.Printf("%d", hash)
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// Output:
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// 2307517237273902113
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```
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