buildkit/vendor/github.com/mitchellh/hashstructure/README.md

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

Installation

Standard go get:

$ go get github.com/mitchellh/hashstructure

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, nil)
if err != nil {
    panic(err)
}

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