pkg/common/utils/hash/hash.go

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package hash

import (
	"fmt"
	"hash"
	"hash/fnv"

	"github.com/davecgh/go-spew/spew"
)

func setHashLabel(labelName string, labels map[string]string, template interface{}) map[string]string {
	if labels == nil {
		labels = map[string]string{}
	}
	labels[labelName] = HashObject(template)
	return labels
}

// HashObject returns a hash of a given object using the 32-bit FNV-1 hash function
// and the spew library to print the object (see WriteHashObject).
// This is inspired by controller revisions in StatefulSets:
// https://github.com/kubernetes/kubernetes/blob/8de1569ddae62e8fab559fe6bd210a5d6100a277/pkg/controller/history/controller_history.go#L89-L101
func HashObject(object interface{}) string { //nolint:revive
	objHash := fnv.New32a()
	WriteHashObject(objHash, object)
	return fmt.Sprint(objHash.Sum32())
}

// WriteHashObject writes specified object to hash using the spew library
// which follows pointers and prints actual values of the nested objects
// ensuring the hash does not change when a pointer changes.
// The hash can be used for object comparisons.
// Copy of https://github.com/kubernetes/kubernetes/blob/ea0764452222146c47ec826977f49d7001b0ea8c/pkg/util/hash/hash.go#L28
func WriteHashObject(hasher hash.Hash, objectToWrite interface{}) {
	printer := spew.ConfigState{
		Indent:         " ",
		SortKeys:       true,
		DisableMethods: true,
		SpewKeys:       true,
	}
	printer.Fprintf(hasher, "%#v", objectToWrite)
}