Improve to avoid heap allocation (#60)

kbsquaredmatrix.go

@@ -14,6 +14,8 @@ type SquaredMatrixKeyboard struct {
 	Pins         []machine.Pin
 	cycleCounter []uint8
 	debounce     uint8
+
+	colsBuf []int
 }
 
 func (d *Device) AddSquaredMatrixKeyboard(pins []machine.Pin, keys [][]Keycode) *SquaredMatrixKeyboard {
@@ -41,6 +43,7 @@ func (d *Device) AddSquaredMatrixKeyboard(pins []machine.Pin, keys [][]Keycode)
 		callback:     func(layer, index int, state State) {},
 		cycleCounter: cycleCnt,
 		debounce:     8,
+		colsBuf:      make([]int, len(pins)),
 	}
 
 	d.kb = append(d.kb, k)
@@ -59,7 +62,7 @@ func (d *SquaredMatrixKeyboard) Callback(layer, index int, state State) {
 
 func (d *SquaredMatrixKeyboard) Get() []State {
 	c := int(0)
-	cols := []int{}
+	cols := d.colsBuf[:0]
 	for i := range d.Pins {
 		for j := range d.Pins {
 			d.Pins[j].Configure(machine.PinConfig{Mode: machine.PinInputPullup})

keyboard.go

@@ -39,6 +39,9 @@ type Device struct {
 	combosReleased []uint32
 	combosKey      uint32
 	combosFounds   []Keycode
+
+	pressToReleaseBuf []uint32
+	noneToPressBuf    []uint32
 }
 
 type KBer interface {
@@ -83,6 +86,9 @@ func New() *Device {
 		combosReleased: make([]uint32, 0, 10),
 		combosKey:      0xFFFFFFFF,
 		combosFounds:   make([]Keycode, 10),
+
+		pressToReleaseBuf: make([]uint32, 0, 20),
+		noneToPressBuf:    make([]uint32, 0, 20),
 	}
 
 	SetDevice(d)
@@ -192,7 +198,7 @@ func (d *Device) GetMaxKeyCount() int {
 }
 
 func (d *Device) Tick() error {
-	pressToRelease := []uint32{}
+	pressToRelease := d.pressToReleaseBuf[:0]
 
 	select {
 	case <-d.flashCh:
@@ -210,7 +216,7 @@ func (d *Device) Tick() error {
 	}
 
 	// read from key matrix
-	noneToPress := []uint32{}
+	noneToPress := d.noneToPressBuf[:0]
 	for kbidx, k := range d.kb {
 		state := k.Get()
 		for i := range state {