initial commit

add internal/xair module

internal/xair/util.go

@@ -0,0 +1,42 @@
+package xair
+
+import "math"
+
+func mustDbInto(db float64) float64 {
+	switch {
+	case db >= 10:
+		return 1
+	case db >= -10:
+		return float64((db + 30) / 40)
+	case db >= -30:
+		return float64((db + 50) / 80)
+	case db >= -60:
+		return float64((db + 70) / 160)
+	case db >= -90:
+		return float64((db + 90) / 480)
+	default:
+		return 0
+	}
+}
+
+func mustDbFrom(level float64) float64 {
+	switch {
+	case level >= 1:
+		return 10
+	case level >= 0.5:
+		return toFixed(float64(level*40)-30, 1)
+	case level >= 0.25:
+		return toFixed(float64(level*80)-50, 1)
+	case level >= 0.0625:
+		return toFixed(float64(level*160)-70, 1)
+	case level >= 0:
+		return toFixed(float64(level*480)-90, 1)
+	default:
+		return -90
+	}
+}
+
+func toFixed(num float64, precision int) float64 {
+	output := math.Pow(10, float64(precision))
+	return float64(math.Round(num*output)) / output
+}