devices: move units code to units.go

No functional change.

I plan to add more units, and eventually this could make sense to split it off
into its own package. For now split it into its own source file.

devices/devices.go

@@ -5,7 +5,6 @@
 package devices
 
 import (
-	"fmt"
 	"image"
 	"image/color"
 	"io"
@@ -49,88 +48,6 @@ type Display interface {
 	Draw(r image.Rectangle, src image.Image, sp image.Point)
 }
 
-// Milli is a fixed point value with 0.001 precision.
-type Milli int32
-
-// Float64 returns the value as float64 with 0.001 precision.
-func (m Milli) Float64() float64 {
-	return float64(m) * .001
-}
-
-// String returns the value formatted as a string.
-func (m Milli) String() string {
-	d := m % 1000
-	if d < 0 {
-		d = -d
-	}
-	return fmt.Sprintf("%d.%03d", m/1000, d)
-}
-
-// Celsius is a temperature at a precision of 0.001°C.
-//
-// Expected range is [-273150, >1000000]
-type Celsius Milli
-
-// Float64 returns the value as float64 with 0.001 precision.
-func (c Celsius) Float64() float64 {
-	return Milli(c).Float64()
-}
-
-// String returns the temperature formatted as a string.
-func (c Celsius) String() string {
-	return Milli(c).String() + "°C"
-}
-
-// ToF returns the temperature as Fahrenheit, a unit used in the United States.
-func (c Celsius) ToF() Fahrenheit {
-	return Fahrenheit((c*9+2)/5 + 32000)
-}
-
-// Fahrenheit is an unsound unit used in the United States.
-type Fahrenheit Milli
-
-// Float64 returns the value as float64 with 0.001 precision.
-func (f Fahrenheit) Float64() float64 {
-	return Milli(f).Float64()
-}
-
-// String returns the temperature formatted as a string.
-func (f Fahrenheit) String() string {
-	return Milli(f).String() + "°F"
-}
-
-// KPascal is pressure at precision of 1Pa.
-//
-// Expected range is [0, >1000000].
-type KPascal Milli
-
-// Float64 returns the value as float64 with 0.001 precision.
-func (k KPascal) Float64() float64 {
-	return Milli(k).Float64()
-}
-
-// String returns the pressure formatted as a string.
-func (k KPascal) String() string {
-	return Milli(k).String() + "KPa"
-}
-
-// RelativeHumidity is humidity level in %rH with 0.01%rH precision.
-type RelativeHumidity int32
-
-// Float64 returns the value in %.
-func (r RelativeHumidity) Float64() float64 {
-	return float64(r) * .01
-}
-
-// String returns the humidity formatted as a string.
-func (r RelativeHumidity) String() string {
-	m := r % 100
-	if m < 0 {
-		m = -m
-	}
-	return fmt.Sprintf("%d.%02d%%rH", r/100, m)
-}
-
 // Environment represents measurements from an environmental sensor.
 type Environment struct {
 	Temperature Celsius

devices/units.go

@@ -0,0 +1,91 @@
+// Copyright 2016 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package devices
+
+import (
+	"fmt"
+)
+
+// Milli is a fixed point value with 0.001 precision.
+type Milli int32
+
+// Float64 returns the value as float64 with 0.001 precision.
+func (m Milli) Float64() float64 {
+	return float64(m) * .001
+}
+
+// String returns the value formatted as a string.
+func (m Milli) String() string {
+	d := m % 1000
+	if d < 0 {
+		d = -d
+	}
+	return fmt.Sprintf("%d.%03d", m/1000, d)
+}
+
+// Celsius is a temperature at a precision of 0.001°C.
+//
+// Expected range is [-273150, >1000000]
+type Celsius Milli
+
+// Float64 returns the value as float64 with 0.001 precision.
+func (c Celsius) Float64() float64 {
+	return Milli(c).Float64()
+}
+
+// String returns the temperature formatted as a string.
+func (c Celsius) String() string {
+	return Milli(c).String() + "°C"
+}
+
+// ToF returns the temperature as Fahrenheit, a unit used in the United States.
+func (c Celsius) ToF() Fahrenheit {
+	return Fahrenheit((c*9+2)/5 + 32000)
+}
+
+// Fahrenheit is an unsound unit used in the United States.
+type Fahrenheit Milli
+
+// Float64 returns the value as float64 with 0.001 precision.
+func (f Fahrenheit) Float64() float64 {
+	return Milli(f).Float64()
+}
+
+// String returns the temperature formatted as a string.
+func (f Fahrenheit) String() string {
+	return Milli(f).String() + "°F"
+}
+
+// KPascal is pressure at precision of 1Pa.
+//
+// Expected range is [0, >1000000].
+type KPascal Milli
+
+// Float64 returns the value as float64 with 0.001 precision.
+func (k KPascal) Float64() float64 {
+	return Milli(k).Float64()
+}
+
+// String returns the pressure formatted as a string.
+func (k KPascal) String() string {
+	return Milli(k).String() + "KPa"
+}
+
+// RelativeHumidity is humidity level in %rH with 0.01%rH precision.
+type RelativeHumidity int32
+
+// Float64 returns the value in %.
+func (r RelativeHumidity) Float64() float64 {
+	return float64(r) * .01
+}
+
+// String returns the humidity formatted as a string.
+func (r RelativeHumidity) String() string {
+	m := r % 100
+	if m < 0 {
+		m = -m
+	}
+	return fmt.Sprintf("%d.%02d%%rH", r/100, m)
+}