[api] Add zero-copy support for noise encryption key requests (#12405)

esphome/components/api/api.proto

@@ -747,7 +747,7 @@ message NoiseEncryptionSetKeyRequest {
   option (source) = SOURCE_CLIENT;
   option (ifdef) = "USE_API_NOISE";
 
-  bytes key = 1;
+  bytes key = 1 [(pointer_to_buffer) = true];
 }
 
 message NoiseEncryptionSetKeyResponse {

esphome/components/api/api_connection.cpp

@@ -1666,13 +1666,13 @@ bool APIConnection::send_noise_encryption_set_key_response(const NoiseEncryption
   resp.success = false;
 
   psk_t psk{};
-  if (msg.key.empty()) {
+  if (msg.key_len == 0) {
     if (this->parent_->clear_noise_psk(true)) {
       resp.success = true;
     } else {
       ESP_LOGW(TAG, "Failed to clear encryption key");
     }
-  } else if (base64_decode(msg.key, psk.data(), psk.size()) != psk.size()) {
+  } else if (base64_decode(msg.key, msg.key_len, psk.data(), psk.size()) != psk.size()) {
     ESP_LOGW(TAG, "Invalid encryption key length");
   } else if (!this->parent_->save_noise_psk(psk, true)) {
     ESP_LOGW(TAG, "Failed to save encryption key");

esphome/components/api/api_pb2.cpp

@@ -858,9 +858,12 @@ void SubscribeLogsResponse::calculate_size(ProtoSize &size) const {
 #ifdef USE_API_NOISE
 bool NoiseEncryptionSetKeyRequest::decode_length(uint32_t field_id, ProtoLengthDelimited value) {
   switch (field_id) {
-    case 1:
-      this->key = value.as_string();
+    case 1: {
+      // Use raw data directly to avoid allocation
+      this->key = value.data();
+      this->key_len = value.size();
       break;
+    }
     default:
       return false;
   }

esphome/components/api/api_pb2.h

@@ -1054,11 +1054,12 @@ class SubscribeLogsResponse final : public ProtoMessage {
 class NoiseEncryptionSetKeyRequest final : public ProtoDecodableMessage {
  public:
   static constexpr uint8_t MESSAGE_TYPE = 124;
-  static constexpr uint8_t ESTIMATED_SIZE = 9;
+  static constexpr uint8_t ESTIMATED_SIZE = 19;
 #ifdef HAS_PROTO_MESSAGE_DUMP
   const char *message_name() const override { return "noise_encryption_set_key_request"; }
 #endif
-  std::string key{};
+  const uint8_t *key{nullptr};
+  uint16_t key_len{0};
 #ifdef HAS_PROTO_MESSAGE_DUMP
   void dump_to(std::string &out) const override;
 #endif

esphome/components/api/api_pb2_dump.cpp

@@ -1115,7 +1115,7 @@ void SubscribeLogsResponse::dump_to(std::string &out) const {
 void NoiseEncryptionSetKeyRequest::dump_to(std::string &out) const {
   MessageDumpHelper helper(out, "NoiseEncryptionSetKeyRequest");
   out.append("  key: ");
-  out.append(format_hex_pretty(reinterpret_cast<const uint8_t *>(this->key.data()), this->key.size()));
+  out.append(format_hex_pretty(this->key, this->key_len));
   out.append("\n");
 }
 void NoiseEncryptionSetKeyResponse::dump_to(std::string &out) const { dump_field(out, "success", this->success); }

esphome/core/helpers.cpp

@@ -479,10 +479,14 @@ std::string base64_encode(const uint8_t *buf, size_t buf_len) {
 }
 
 size_t base64_decode(const std::string &encoded_string, uint8_t *buf, size_t buf_len) {
-  int in_len = encoded_string.size();
+  return base64_decode(reinterpret_cast<const uint8_t *>(encoded_string.data()), encoded_string.size(), buf, buf_len);
+}
+
+size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len) {
+  size_t in_len = encoded_len;
   int i = 0;
   int j = 0;
-  int in = 0;
+  size_t in = 0;
   size_t out = 0;
   uint8_t char_array_4[4], char_array_3[3];
   bool truncated = false;
@@ -490,8 +494,8 @@ size_t base64_decode(const std::string &encoded_string, uint8_t *buf, size_t buf
   // SAFETY: The loop condition checks is_base64() before processing each character.
   // This ensures base64_find_char() is only called on valid base64 characters,
   // preventing the edge case where invalid chars would return 0 (same as 'A').
-  while (in_len-- && (encoded_string[in] != '=') && is_base64(encoded_string[in])) {
-    char_array_4[i++] = encoded_string[in];
+  while (in_len-- && (encoded_data[in] != '=') && is_base64(encoded_data[in])) {
+    char_array_4[i++] = encoded_data[in];
     in++;
     if (i == 4) {
       for (i = 0; i < 4; i++)

esphome/core/helpers.h

@@ -878,6 +878,7 @@ std::string base64_encode(const std::vector<uint8_t> &buf);
 
 std::vector<uint8_t> base64_decode(const std::string &encoded_string);
 size_t base64_decode(std::string const &encoded_string, uint8_t *buf, size_t buf_len);
+size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len);
 
 ///@}