encoder: change casting for float64 values to handle negative values on different architectures than amd64.

This is required in order to handle running Go on ARM processors, as well as for other compilers such as TinyGo,
which is specifically where I initially ran into it.

See golang/go#43047 for a description of the underlying Go issue.

Signed-off-by: deadprogram <[email protected]>

Author: deadprogram

decoder_test.go

@@ -86,6 +86,7 @@ func TestDecode(t *testing.T) {
 			10, BarometricPressure, 41, 239,
 			11, Gyrometer, 1, 99, 2, 49, 254, 102,
 			12, GPS, 7, 253, 135, 0, 190, 245, 0, 8, 106,
+			13, GPS, 7, 253, 135, 255, 65, 12, 0, 8, 106,
 		}
 		decoder := NewDecoder(bytes.NewBuffer(buf))
 		target := &target{make(map[uint8]interface{})}
@@ -104,6 +105,7 @@ func TestDecode(t *testing.T) {
 		a.So(target.values[10], ShouldEqual, 1073.5)
 		a.So(target.values[11], ShouldResemble, []float64{3.55, 5.61, -4.10})
 		a.So(target.values[12], ShouldResemble, []float64{52.3655, 4.8885, 21.54})
+		a.So(target.values[13], ShouldResemble, []float64{52.3655, -4.8884, 21.54})
 	}
 
 	// Happy flow: downlink

encoder.go

@@ -58,7 +58,7 @@ func (e *encoder) WriteTo(w io.Writer) (int64, error) {
 }
 
 func (e *encoder) AddPort(channel uint8, value float64) {
-	val := uint16(value * 100)
+	val := int16(value * 100)
 	e.buf.WriteByte(channel)
 	binary.Write(e.buf, binary.BigEndian, val)
 }
@@ -76,14 +76,14 @@ func (e *encoder) AddDigitalOutput(channel, value uint8) {
 }
 
 func (e *encoder) AddAnalogInput(channel uint8, value float64) {
-	val := uint16(value * 100)
+	val := int16(value * 100)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(AnalogInput)
 	binary.Write(e.buf, binary.BigEndian, val)
 }
 
 func (e *encoder) AddAnalogOutput(channel uint8, value float64) {
-	val := uint16(value * 100)
+	val := int16(value * 100)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(AnalogOutput)
 	binary.Write(e.buf, binary.BigEndian, val)
@@ -102,7 +102,7 @@ func (e *encoder) AddPresence(channel, value uint8) {
 }
 
 func (e *encoder) AddTemperature(channel uint8, celcius float64) {
-	val := uint16(celcius * 10)
+	val := int16(celcius * 10)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(Temperature)
 	binary.Write(e.buf, binary.BigEndian, val)
@@ -115,9 +115,9 @@ func (e *encoder) AddRelativeHumidity(channel uint8, rh float64) {
 }
 
 func (e *encoder) AddAccelerometer(channel uint8, x, y, z float64) {
-	valX := uint16(x * 1000)
-	valY := uint16(y * 1000)
-	valZ := uint16(z * 1000)
+	valX := int16(x * 1000)
+	valY := int16(y * 1000)
+	valZ := int16(z * 1000)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(Accelerometer)
 	binary.Write(e.buf, binary.BigEndian, valX)
@@ -126,16 +126,16 @@ func (e *encoder) AddAccelerometer(channel uint8, x, y, z float64) {
 }
 
 func (e *encoder) AddBarometricPressure(channel uint8, hpa float64) {
-	val := uint16(hpa * 10)
+	val := int16(hpa * 10)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(BarometricPressure)
 	binary.Write(e.buf, binary.BigEndian, val)
 }
 
 func (e *encoder) AddGyrometer(channel uint8, x, y, z float64) {
-	valX := uint16(x * 100)
-	valY := uint16(y * 100)
-	valZ := uint16(z * 100)
+	valX := int16(x * 100)
+	valY := int16(y * 100)
+	valZ := int16(z * 100)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(Gyrometer)
 	binary.Write(e.buf, binary.BigEndian, valX)
@@ -144,18 +144,18 @@ func (e *encoder) AddGyrometer(channel uint8, x, y, z float64) {
 }
 
 func (e *encoder) AddGPS(channel uint8, latitude, longitude, meters float64) {
-	valLat := uint32(latitude * 10000)
-	valLon := uint32(longitude * 10000)
-	valAlt := uint32(meters * 100)
+	valLat := int32(latitude * 10000)
+	valLon := int32(longitude * 10000)
+	valAlt := int32(meters * 100)
 	e.buf.WriteByte(channel)
 	e.buf.WriteByte(GPS)
-	e.buf.WriteByte(uint8(valLat >> 16))
-	e.buf.WriteByte(uint8(valLat >> 8))
-	e.buf.WriteByte(uint8(valLat))
-	e.buf.WriteByte(uint8(valLon >> 16))
-	e.buf.WriteByte(uint8(valLon >> 8))
-	e.buf.WriteByte(uint8(valLon))
-	e.buf.WriteByte(uint8(valAlt >> 16))
-	e.buf.WriteByte(uint8(valAlt >> 8))
-	e.buf.WriteByte(uint8(valAlt))
+	e.buf.WriteByte(byte(valLat >> 16))
+	e.buf.WriteByte(byte(valLat >> 8))
+	e.buf.WriteByte(byte(valLat))
+	e.buf.WriteByte(byte(valLon >> 16))
+	e.buf.WriteByte(byte(valLon >> 8))
+	e.buf.WriteByte(byte(valLon))
+	e.buf.WriteByte(byte(valAlt >> 16))
+	e.buf.WriteByte(byte(valAlt >> 8))
+	e.buf.WriteByte(byte(valAlt))
 }

encoder_test.go

@@ -51,6 +51,9 @@ func TestEncode(t *testing.T) {
 
 		e.AddGPS(12, 52.3655, 4.8885, 21.54)
 		a.So(e.Bytes()[48:59], ShouldResemble, []byte{12, GPS, 7, 253, 135, 0, 190, 244, 0, 8, 106})
+
+		e.AddGPS(13, 43.43382, -5.865784, 179.0000)
+		a.So(e.Bytes()[59:70], ShouldResemble, []byte{13, GPS, 0x06, 160, 162, 255, 26, 223, 0, 69, 236})
 	}
 
 	// Downlink encoding