Too many things for a single commit but in summary:

We got them data bytes computer majigs being transmitted to the display
and correctly parsed over there. Also seems to be fast. I won't touch
performance issues until I have this working and documented tho.

telemetry/data.go

@@ -3,9 +3,31 @@ package telemetry
 import (
 	"math"
 	"strconv"
+	"sync"
 	"time"
 )
 
+type FieldMapper struct {
+	SDKKey    string
+	DataType  DataType
+	Transform func(any) uint64
+}
+
+// NOTE: Update the iracing SDK to write data to the same map ALWAYS, then
+// I can bind that address and read directly from there on the transform
+type BoundField struct {
+	Key       string
+	ID        FieldID
+	Transform func(any, *TelemetryField)
+}
+
+var bufferPool = sync.Pool{
+	New: func() any {
+		b := make([]byte, 0, MaxFields*8)
+		return &b
+	},
+}
+
 type DataType uint8
 
 const (
@@ -40,33 +62,33 @@ type TelemetryField struct {
 // or
 // 0x02 - str len max is 255 chars
 // [0x02] - str
-func (tf *TelemetryField) Pack() []byte {
+func (tf *TelemetryField) Pack(dest []byte) []byte {
 	// NOTE: maybe we can have a pool of these so we don't have to create them here
 	// or whatever
-	buf := make([]byte, 0, 8)
-
-	buf = append(buf, uint8(tf.Type))
+	dest = append(dest, uint8(tf.Type))
 
 	switch tf.Type {
 	case DataTypeINT8, DataTypeUINT8:
-		buf = append(buf, uint8(tf.Raw))
+		dest = append(dest, uint8(tf.Raw))
 	case DataTypeINT16, DataTypeUINT16:
-		buf = append(buf, uint8(tf.Raw), uint8(tf.Raw>>8))
+		dest = append(dest, uint8(tf.Raw), uint8(tf.Raw>>8))
 	case DataTypeINT32, DataTypeUINT32:
-		buf = append(buf, uint8(tf.Raw), uint8(tf.Raw>>8), uint8(tf.Raw>>16))
+		dest = append(dest, uint8(tf.Raw), uint8(tf.Raw>>8), uint8(tf.Raw>>16))
 	case DataTypeINT64, DataTypeUINT64:
-		buf = append(buf, uint8(tf.Raw), uint8(tf.Raw>>8), uint8(tf.Raw>>16),
+		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 DataTypeSTRING:
 		l := min(len(tf.Str), math.MaxUint8)
 
-		buf = append(buf, uint8(l))
-		buf = append(buf, tf.Str[:l]...)
+		dest = append(dest, uint8(l))
+		dest = append(dest, tf.Str[:l]...)
+	case DataTypeCHAR:
+		dest = append(dest, uint8(tf.Raw))
 	}
 
-	return buf
+	return dest
 }
 
 func (tf *TelemetryField) String() string {
@@ -134,6 +156,7 @@ func GetFieldID(name string) (FieldID, bool) {
 type TelemetryData struct {
 	// Values map[string]*TelemetryField
 	Values              [MaxFields]TelemetryField
+	ActiveBinds         []BoundField
 	InitialTime         time.Time
 	PenultimateDataPoll time.Time
 	LastDataPoll        time.Time
@@ -142,3 +165,20 @@ type TelemetryData struct {
 func NewTelemetryData() *TelemetryData {
 	return &TelemetryData{}
 }
+
+func (td *TelemetryData) Pack() []byte {
+	bufPtr := bufferPool.Get().(*[]byte)
+	buf := (*bufPtr)[:0]
+
+	for _, bind := range td.ActiveBinds {
+		buf = td.Values[bind.ID].Pack(buf)
+	}
+
+	// We have to copy here because we have to return the buffer
+	result := make([]byte, len(buf))
+	copy(result, buf)
+
+	bufferPool.Put(&buf)
+
+	return result
+}