[e131] Remove unnecessary heap allocation from packet receive loop

The received data was already in stack buffer buf[1460], but was being
copied into a std::vector just to satisfy the packet_() signature.
E1.31 runs at up to 44 Hz per universe, so this caused ~44 alloc/free
cycles per second per universe.

Change packet_() to accept const uint8_t* + size_t and pass the stack
buffer directly. This is an internal method so there is no API breakage.

esphome/components/e131/e131.cpp

@@ -55,7 +55,6 @@ void E131Component::setup() {
 }
 
 void E131Component::loop() {
-  std::vector<uint8_t> payload;
   E131Packet packet;
   int universe = 0;
   uint8_t buf[1460];
@@ -64,11 +63,9 @@ void E131Component::loop() {
   if (len == -1) {
     return;
   }
-  payload.resize(len);
-  memmove(&payload[0], buf, len);
 
-  if (!this->packet_(payload, universe, packet)) {
-    ESP_LOGV(TAG, "Invalid packet received of size %zu.", payload.size());
+  if (!this->packet_(buf, (size_t) len, universe, packet)) {
+    ESP_LOGV(TAG, "Invalid packet received of size %zd.", len);
     return;
   }
 

esphome/components/e131/e131.h

@@ -38,7 +38,7 @@ class E131Component : public esphome::Component {
   void set_method(E131ListenMethod listen_method) { this->listen_method_ = listen_method; }
 
  protected:
-  bool packet_(const std::vector<uint8_t> &data, int &universe, E131Packet &packet);
+  bool packet_(const uint8_t *data, size_t len, int &universe, E131Packet &packet);
   bool process_(int universe, const E131Packet &packet);
   bool join_igmp_groups_();
   void join_(int universe);

esphome/components/e131/e131_packet.cpp

@@ -116,11 +116,11 @@ void E131Component::leave_(int universe) {
   ESP_LOGD(TAG, "Left %d universe for E1.31.", universe);
 }
 
-bool E131Component::packet_(const std::vector<uint8_t> &data, int &universe, E131Packet &packet) {
-  if (data.size() < E131_MIN_PACKET_SIZE)
+bool E131Component::packet_(const uint8_t *data, size_t len, int &universe, E131Packet &packet) {
+  if (len < E131_MIN_PACKET_SIZE)
     return false;
 
-  auto *sbuff = reinterpret_cast<const E131RawPacket *>(&data[0]);
+  auto *sbuff = reinterpret_cast<const E131RawPacket *>(data);
 
   if (memcmp(sbuff->acn_id, ACN_ID, sizeof(sbuff->acn_id)) != 0)
     return false;

esphome/components/epaper_spi/epaper_spi_spectra_e6.h

@@ -4,7 +4,7 @@
 
 namespace esphome::epaper_spi {
 
-class EPaperSpectraE6 : public EPaperBase {
+class EPaperSpectraE6 final : public EPaperBase {
  public:
   EPaperSpectraE6(const char *name, uint16_t width, uint16_t height, const uint8_t *init_sequence,
                   size_t init_sequence_length)

esphome/components/epaper_spi/epaper_waveshare.h

@@ -6,7 +6,7 @@ namespace esphome::epaper_spi {
 /**
  * An epaper display that needs LUTs to be sent to it.
  */
-class EpaperWaveshare : public EPaperMono {
+class EpaperWaveshare final : public EPaperMono {
  public:
   EpaperWaveshare(const char *name, uint16_t width, uint16_t height, const uint8_t *init_sequence,
                   size_t init_sequence_length, const uint8_t *lut, size_t lut_length, const uint8_t *partial_lut,