decoupled the winIDs from the telemetry data

hell yeah, brother!

devices/cdashdisplay/transportPackets.go

@@ -1,5 +1,11 @@
 package cdashdisplay
 
+import (
+	"math"
+
+	"esdi/telemetry"
+)
+
 // In this file we will place all structs that are 1:1 representation of the
 // types in the device transport layer ->
 
@@ -65,6 +71,71 @@ type UIWindowUpdatePacket struct {
 	Window UIWindow
 }
 
-// func getUIWindowDTO(w *DesktopWindowData) *UIWindow {
-//
-// }
+// TODO: this is here because this is the only device I use like this
+// once I add another serial device I will move this somewhere else that can
+// be reused by all devices but still is decoupled from the telemetry package
+func (cds *CDashDisplay) encodePacket(td *telemetry.TelemetryData) []byte {
+	bufPtr := cds.bufPool.Get().(*[]byte)
+	buf := (*bufPtr)[:0]
+
+	for fieldID, windowIDs := range cds.fieldToWindows {
+		if int(fieldID) >= len(td.Values) || len(windowIDs) == 0 {
+			continue
+		}
+
+		tf := &td.Values[fieldID]
+
+		for _, winID := range windowIDs {
+			buf = packField(winID, tf, buf)
+		}
+	}
+
+	// We have to copy here because we have to return the buffer
+	result := make([]byte, len(buf))
+	copy(result, buf)
+
+	cds.bufPool.Put(&buf)
+
+	return result
+}
+
+// Pack will pack this current TelemetryField into bytes to send over the wire
+// Format:
+// 0x00 - Field ID
+// 0x00 |
+// 0x01 - DataType
+// 0x02 - if its a (u)int8
+// or
+// 0x02 - if its a (u)int16 - first byte
+// 0x02 - if its a (u)int16 - second byte
+// or
+// 0x02 - str len max is 255 chars
+// [0x02] - str
+func packField(winID int16, tf *telemetry.TelemetryField, dest []byte) []byte {
+	// NOTE: maybe we can have a pool of these so we don't have to create them here
+	// or whatever
+	dest = append(dest, uint8(winID), uint8(winID>>8))
+	dest = append(dest, uint8(tf.Type))
+
+	switch tf.Type {
+	case telemetry.DataTypeINT8, telemetry.DataTypeUINT8, telemetry.DataTypeCHAR:
+		dest = append(dest, uint8(tf.Raw))
+	case telemetry.DataTypeINT16, telemetry.DataTypeUINT16:
+		dest = append(dest, uint8(tf.Raw), uint8(tf.Raw>>8))
+	case telemetry.DataTypeINT32, telemetry.DataTypeUINT32:
+		dest = append(dest, uint8(tf.Raw), uint8(tf.Raw>>8), uint8(tf.Raw>>16), uint8(tf.Raw>>24))
+	case telemetry.DataTypeINT64, telemetry.DataTypeUINT64:
+		dest = append(
+			dest, uint8(tf.Raw), uint8(tf.Raw>>8), uint8(tf.Raw>>16),
+			uint8(tf.Raw>>24), uint8(tf.Raw>>32), uint8(tf.Raw>>40), uint8(tf.Raw>>48),
+			uint8(tf.Raw>>56),
+		)
+	case telemetry.DataTypeSTRING:
+		l := min(len(tf.Str), math.MaxUint8)
+
+		dest = append(dest, uint8(l))
+		dest = append(dest, tf.Str[:l]...)
+	}
+
+	return dest
+}