hashstructure

hashstructure

hashstructure is a Go library for creating a unique hash value for arbitrary values in Go.

This can be used to key values in a hash (for use in a map, set, etc.) that are complex. The most common use case is comparing two values without sending data across the network, caching values locally (de-dup), and so on.

Features

• Hash any arbitrary Go value, including complex types.

• Tag a struct field to ignore it and not affect the hash value.

• Tag a slice type struct field to treat it as a set where ordering doesn't affect the hash code but the field itself is still taken into account to create the hash value.

• Optionally, specify a custom hash function to optimize for speed, collision avoidance for your data set, etc.

• Optionally, hash the output of .String() on structs that implement fmt.Stringer, allowing effective hashing of time.Time

• Optionally, override the hashing process by implementing Hashable.

Installation

Standard go get:

$ go get github.com/mitchellh/hashstructure/v2

Note on v2: It is highly recommended you use the "v2" release since this fixes some significant hash collisions issues from v1. In practice, we used v1 for many years in real projects at HashiCorp and never had issues, but it is highly dependent on the shape of the data you're hashing and how you use those hashes.

When using v2+, you can still generate weaker v1 hashes by using the FormatV1 format when calling Hash.

Usage & Example

For usage and examples see the Godoc.

A quick code example is shown below:

type ComplexStruct struct {
    Name     string
    Age      uint
    Metadata map[string]interface{}
}

v := ComplexStruct{
    Name: "mitchellh",
    Age:  64,
    Metadata: map[string]interface{}{
        "car":      true,
        "location": "California",
        "siblings": []string{"Bob", "John"},
    },
}

hash, err := hashstructure.Hash(v, hashstructure.FormatV2, nil)
if err != nil {
    panic(err)
}

fmt.Printf("%d", hash)
// Output:
// 2307517237273902113