1 files changed, 58 insertions, 0 deletions
diff --git a/pressure/pressure.go b/pressure/pressure.go
new file mode 100644
index 0000000..2948c72
--- /dev/null
+++ b/pressure/pressure.go
@@ -0,0 +1,58 @@
+package pressure
+
+import (
+	"errors"
+	"fmt"
+)
+
+type unit float32
+
+const (
+	Pascal              unit = 1
+	Kilopascal          unit = 1_000
+	Bar                 unit = 100_000
+	PoundsPerSquareInch unit = 6_894.757
+)
+
+// UnitStrings returns a slice of strings, each representing a
+// unit.
+// This is necessary because giu.Combo only works with strings.
+func UnitStrings() []string {
+	return []string{"Pa", "kPa", "bar", "psi"}
+}
+
+const (
+	DefaultUnit unit = Kilopascal
+	// DefaultUnitIndex is used to index UnitStrings().
+	DefaultUnitIndex int32 = 1 // kPa
+)
+
+func UnitFromString(s string) (unit, error) {
+	// Each case corresponds to a value in UnitStrings().
+	switch s {
+	case "Pa":
+		return Pascal, nil
+	case "kPa":
+		return Kilopascal, nil
+	case "bar":
+		return Bar, nil
+	case "psi":
+		return PoundsPerSquareInch, nil
+	default:
+		return *new(unit), errors.New(fmt.Sprintf("invalid unit: '%s'", s))
+	}
+}
+
+type Pressure struct {
+	Val  float32
+	Unit unit
+}
+
+func (p Pressure) AsUnit(u unit) float32 {
+	pa := p.Val * float32(p.Unit) // Convert to pascals.
+	return pa / float32(u)        // Convert to desired unit.
+}
+
+func Atmospheric() Pressure {
+	return Pressure{1, Bar}
+}