hst/container: flags string representation

This is useful for a user-facing representation other than JSON. This also gets rid of the ugly, outdated flags string builder in cmd/hakurei.

Signed-off-by: Ophestra <cat@gensokyo.uk>

hst/container.go

@@ -2,6 +2,7 @@ package hst
 
 import (
 	"encoding/json"
+	"strings"
 	"syscall"
 	"time"
 
@@ -38,9 +39,12 @@ const (
 	ExitRequest = 254
 )
 
+// Flags are options held by [ContainerConfig].
+type Flags uintptr
+
 const (
 	// FMultiarch unblocks syscalls required for multiarch to work on applicable targets.
-	FMultiarch uintptr = 1 << iota
+	FMultiarch Flags = 1 << iota
 
 	// FSeccompCompat changes emitted seccomp filter programs to be identical to that of Flatpak.
 	FSeccompCompat
@@ -74,6 +78,45 @@ const (
 	FAll = fMax - 1
 )
 
+func (flags Flags) String() string {
+	switch flags {
+	case FMultiarch:
+		return "multiarch"
+	case FSeccompCompat:
+		return "compat"
+	case FDevel:
+		return "devel"
+	case FUserns:
+		return "userns"
+	case FHostNet:
+		return "net"
+	case FHostAbstract:
+		return "abstract"
+	case FTty:
+		return "tty"
+	case FMapRealUID:
+		return "mapuid"
+	case FDevice:
+		return "device"
+	case FShareRuntime:
+		return "runtime"
+	case FShareTmpdir:
+		return "tmpdir"
+
+	default:
+		s := make([]string, 0, 1<<4)
+		for f := Flags(1); f < fMax; f <<= 1 {
+			if flags&f != 0 {
+				s = append(s, f.String())
+			}
+		}
+		if len(s) == 0 {
+			return "none"
+		}
+		return strings.Join(s, ", ")
+	}
+}
+
 // ContainerConfig describes the container configuration to be applied to an underlying [container].
 type ContainerConfig struct {
 	// Container UTS namespace hostname.
@@ -106,7 +149,7 @@ type ContainerConfig struct {
 	Args []string `json:"args"`
 
 	// Flags holds boolean options of [ContainerConfig].
-	Flags uintptr `json:"-"`
+	Flags Flags `json:"-"`
 }
 
 // ContainerConfigF is [ContainerConfig] stripped of its methods.

hst/container_test.go

@@ -3,6 +3,7 @@ package hst_test
 import (
 	"encoding/json"
 	"errors"
+	"math"
 	"reflect"
 	"syscall"
 	"testing"
@@ -10,6 +11,30 @@ import (
 	"hakurei.app/hst"
 )
 
+func TestFlagsString(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name  string
+		flags hst.Flags
+		want  string
+	}{
+		{"none", 0, "none"},
+		{"none high", hst.FAll + 1, "none"},
+		{"all", hst.FAll, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir"},
+		{"all high", math.MaxUint, "multiarch, compat, devel, userns, net, abstract, tty, mapuid, device, runtime, tmpdir"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			if got := tc.flags.String(); got != tc.want {
+				t.Errorf("String(%#b): %q, want %q", tc.flags, got, tc.want)
+			}
+		})
+	}
+}
+
 func TestContainerConfig(t *testing.T) {
 	t.Parallel()