copy k8snamehash function to library

Author: Diaphteiros

README.md

@@ -103,6 +103,9 @@ The `pkg/controller` package contains useful functions for setting up and runnin
 #### Noteworthy Functions
 
 - `LoadKubeconfig` creates a REST config for accessing a k8s cluster. It can be used with a path to a kubeconfig file, or a directory containing files for a trust relationship. When called with an empty path, it returns the in-cluster configuration.
+- There are some functions useful for working with annotations and labels, e.g. `HasAnnotationWithValue` or `EnsureLabel`.
+- There are multiple predefined predicates to help with filtering reconciliation triggers in controllers, e.g. `HasAnnotationPredicate` or `DeletionTimestampChangedPredicate`.
+- The `K8sNameHash` function can be used to create a hash that can be used as a name for k8s resources.
 
 ### logging
 

pkg/controller/utils.go

@@ -0,0 +1,37 @@
+package controller
+
+import (
+	"crypto/sha1"
+	"encoding/base32"
+	"reflect"
+	"strings"
+)
+
+const (
+	maxLength                int = 63
+	Base32EncodeStdLowerCase     = "abcdefghijklmnopqrstuvwxyz234567"
+)
+
+// K8sNameHash takes any number of string arguments and computes a hash out of it, which is then base32-encoded to be a valid k8s resource name.
+// The arguments are joined with '/' before being hashed.
+func K8sNameHash(ids ...string) string {
+	name := strings.Join(ids, "/")
+	h := sha1.New()
+	_, _ = h.Write([]byte(name))
+	// we need base32 encoding as some base64 (even url safe base64) characters are not supported by k8s
+	// see https://kubernetes.io/docs/concepts/overview/working-with-objects/names/
+	return base32.NewEncoding(Base32EncodeStdLowerCase).WithPadding(base32.NoPadding).EncodeToString(h.Sum(nil))
+}
+
+// IsNil checks if a given pointer is nil.
+// Opposed to 'i == nil', this works for typed and untyped nil values.
+func IsNil(i any) bool {
+	if i == nil {
+		return true
+	}
+	switch reflect.TypeOf(i).Kind() {
+	case reflect.Ptr, reflect.Map, reflect.Array, reflect.Chan, reflect.Slice:
+		return reflect.ValueOf(i).IsNil()
+	}
+	return false
+}