feat: new, shorter hash function for k8s resource names (#141)

* new, shorter hash function for k8s resource names

* improve comment

* typo

Author: ValentinGerlach

pkg/controller/hash.go

@@ -2,6 +2,7 @@ package controller
 
 import (
 	"crypto/sha3"
+	"encoding/base32"
 	"errors"
 	"fmt"
 	"strings"
@@ -90,3 +91,25 @@ func K8sObjectUUIDUnsafe(obj client.Object) string {
 	}
 	return uuid
 }
+
+// NameHashSHAKE128Base32 takes any number of string arguments and computes a hash out of it. The output string will be 8 characters long.
+// The arguments are joined with '/' before being hashed.
+func NameHashSHAKE128Base32(names ...string) string {
+	name := strings.Join(names, "/")
+
+	// Desired output length = 8 chars
+	// 8 chars * 5 bits (base32) / 8 bits per byte = 5 bytes
+	hash := sha3.SumSHAKE128([]byte(name), 5)
+
+	return base32.NewEncoding(Base32EncodeStdLowerCase).WithPadding(base32.NoPadding).EncodeToString(hash)
+}
+
+// ObjectHashSHAKE128Base32 takes a client object and computes a hash out of the namespace and name. The output string will be 8 characters long.
+// An empty namespace will be replaced by "default".
+func ObjectHashSHAKE128Base32(obj client.Object) string {
+	name, namespace := obj.GetName(), obj.GetNamespace()
+	if namespace == "" {
+		namespace = corev1.NamespaceDefault
+	}
+	return NameHashSHAKE128Base32(namespace, name)
+}

pkg/controller/hash_test.go

@@ -2,6 +2,7 @@ package controller
 
 import (
 	"crypto/sha3"
+	"strings"
 	"testing"
 
 	"github.com/google/uuid"
@@ -132,3 +133,59 @@ func Test_K8sObjectUUID(t *testing.T) {
 		})
 	}
 }
+
+func Test_NameHashSHAKE128Base32(t *testing.T) {
+	testCases := []struct {
+		input    []string
+		expected string
+	}{
+		{
+			input:    []string{"example"},
+			expected: "epgccknc",
+		},
+		{
+			input:    []string{corev1.NamespaceDefault, "example"},
+			expected: "fphxsdub",
+		},
+	}
+	for _, tC := range testCases {
+		t.Run(strings.Join(tC.input, " "), func(t *testing.T) {
+			actual := NameHashSHAKE128Base32(tC.input...)
+			assert.Equal(t, tC.expected, actual)
+		})
+	}
+}
+
+func Test_ObjectHashSHAKE128Base32(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		obj      client.Object
+		expected string
+	}{
+		{
+			desc: "should work with config map",
+			obj: &corev1.ConfigMap{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "example",
+					Namespace: "default",
+				},
+			},
+			expected: "fphxsdub", // same as in Test_K8sNameUUID
+		},
+		{
+			desc: "should work with config map and empty namespace",
+			obj: &corev1.ConfigMap{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "example",
+				},
+			},
+			expected: "fphxsdub", // same as above
+		},
+	}
+	for _, tC := range testCases {
+		t.Run(tC.desc, func(t *testing.T) {
+			actual := ObjectHashSHAKE128Base32(tC.obj)
+			assert.Equal(t, tC.expected, actual)
+		})
+	}
+}