system: optimise string formatting

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

system/enablement.go

@@ -1,68 +1,47 @@
 package system
 
 import (
+	"fmt"
 	"strings"
 )
 
-type (
-	// Enablement represents an optional system resource
-	Enablement uint8
-	// Enablements represents optional system resources to share
-	Enablements uint64
-)
+// Enablement represents optional system resources.
+type Enablement byte
 
 const (
-	EWayland Enablement = iota
+	EWayland Enablement = 1 << iota
 	EX11
 	EDBus
 	EPulse
+
+	EM
 )
 
-var enablementString = [...]string{
-	EWayland: "Wayland",
-	EX11:     "X11",
-	EDBus:    "D-Bus",
-	EPulse:   "PulseAudio",
-}
-
-const ELen = len(enablementString)
-
 func (e Enablement) String() string {
-	if int(e) >= ELen {
-		return "<invalid enablement>"
-	}
-	return enablementString[e]
-}
+	switch e {
+	case 0:
+		return "(no enablements)"
+	case EWayland:
+		return "wayland"
+	case EX11:
+		return "x11"
+	case EDBus:
+		return "dbus"
+	case EPulse:
+		return "pulseaudio"
+	default:
+		buf := new(strings.Builder)
+		buf.Grow(32)
 
-func (e Enablement) Mask() Enablements {
-	return 1 << e
-}
-
-// Has returns whether a feature is enabled
-func (es *Enablements) Has(e Enablement) bool {
-	return *es&e.Mask() != 0
-}
-
-// Set enables a feature
-func (es *Enablements) Set(e Enablement) {
-	if es.Has(e) {
-		panic("enablement " + e.String() + " set twice")
-	}
-
-	*es |= e.Mask()
-}
-
-func (es *Enablements) String() string {
-	buf := new(strings.Builder)
-	for i := Enablement(0); i < Enablement(ELen); i++ {
-		if es.Has(i) {
-			buf.WriteString(", " + i.String())
+		for i := Enablement(1); i < EM; i <<= 1 {
+			if e&i != 0 {
+				buf.WriteString(", " + i.String())
+			}
 		}
-	}
 
-	if buf.Len() == 0 {
-		buf.WriteString("(No enablements)")
+		if buf.Len() == 0 {
+			return fmt.Sprintf("e%x", byte(e))
+		}
+		return strings.TrimPrefix(buf.String(), ", ")
 	}
-
-	return strings.TrimPrefix(buf.String(), ", ")
 }