[api] Optimize message buffer allocation and eliminate redundant methods (#10231)

esphome/components/api/api_connection.cpp

@@ -289,16 +289,26 @@ uint16_t APIConnection::encode_message_to_buffer(ProtoMessage &msg, uint8_t mess
     return 0;  // Doesn't fit
   }
 
-  // Allocate buffer space - pass payload size, allocation functions add header/footer space
-  ProtoWriteBuffer buffer = is_single ? conn->allocate_single_message_buffer(calculated_size)
-                                      : conn->allocate_batch_message_buffer(calculated_size);
-
   // Get buffer size after allocation (which includes header padding)
   std::vector<uint8_t> &shared_buf = conn->parent_->get_shared_buffer_ref();
-  size_t size_before_encode = shared_buf.size();
+
+  if (is_single || conn->flags_.batch_first_message) {
+    // Single message or first batch message
+    conn->prepare_first_message_buffer(shared_buf, header_padding, total_calculated_size);
+    if (conn->flags_.batch_first_message) {
+      conn->flags_.batch_first_message = false;
+    }
+  } else {
+    // Batch message second or later
+    // Add padding for previous message footer + this message header
+    size_t current_size = shared_buf.size();
+    shared_buf.reserve(current_size + total_calculated_size);
+    shared_buf.resize(current_size + footer_size + header_padding);
+  }
 
   // Encode directly into buffer
-  msg.encode(buffer);
+  size_t size_before_encode = shared_buf.size();
+  msg.encode({&shared_buf});
 
   // Calculate actual encoded size (not including header that was already added)
   size_t actual_payload_size = shared_buf.size() - size_before_encode;
@@ -1620,14 +1630,6 @@ bool APIConnection::schedule_batch_() {
   return true;
 }
 
-ProtoWriteBuffer APIConnection::allocate_single_message_buffer(uint16_t size) { return this->create_buffer(size); }
-
-ProtoWriteBuffer APIConnection::allocate_batch_message_buffer(uint16_t size) {
-  ProtoWriteBuffer result = this->prepare_message_buffer(size, this->flags_.batch_first_message);
-  this->flags_.batch_first_message = false;
-  return result;
-}
-
 void APIConnection::process_batch_() {
   // Ensure PacketInfo remains trivially destructible for our placement new approach
   static_assert(std::is_trivially_destructible<PacketInfo>::value,
@@ -1735,7 +1737,7 @@ void APIConnection::process_batch_() {
     }
     remaining_size -= payload_size;
     // Calculate where the next message's header padding will start
-    // Current buffer size + footer space (that prepare_message_buffer will add for this message)
+    // Current buffer size + footer space for this message
     current_offset = shared_buf.size() + footer_size;
   }
 

esphome/components/api/api_connection.h

@@ -252,44 +252,21 @@ class APIConnection : public APIServerConnection {
 
     // Get header padding size - used for both reserve and insert
     uint8_t header_padding = this->helper_->frame_header_padding();
-
     // Get shared buffer from parent server
     std::vector<uint8_t> &shared_buf = this->parent_->get_shared_buffer_ref();
+    this->prepare_first_message_buffer(shared_buf, header_padding,
+                                       reserve_size + header_padding + this->helper_->frame_footer_size());
+    return {&shared_buf};
+  }
+
+  void prepare_first_message_buffer(std::vector<uint8_t> &shared_buf, size_t header_padding, size_t total_size) {
     shared_buf.clear();
     // Reserve space for header padding + message + footer
     // - Header padding: space for protocol headers (7 bytes for Noise, 6 for Plaintext)
     // - Footer: space for MAC (16 bytes for Noise, 0 for Plaintext)
-    shared_buf.reserve(reserve_size + header_padding + this->helper_->frame_footer_size());
+    shared_buf.reserve(total_size);
     // Resize to add header padding so message encoding starts at the correct position
     shared_buf.resize(header_padding);
-    return {&shared_buf};
-  }
-
-  // Prepare buffer for next message in batch
-  ProtoWriteBuffer prepare_message_buffer(uint16_t message_size, bool is_first_message) {
-    // Get reference to shared buffer (it maintains state between batch messages)
-    std::vector<uint8_t> &shared_buf = this->parent_->get_shared_buffer_ref();
-
-    if (is_first_message) {
-      shared_buf.clear();
-    }
-
-    size_t current_size = shared_buf.size();
-
-    // Calculate padding to add:
-    // - First message: just header padding
-    // - Subsequent messages: footer for previous message + header padding for this message
-    size_t padding_to_add = is_first_message
-                                ? this->helper_->frame_header_padding()
-                                : this->helper_->frame_header_padding() + this->helper_->frame_footer_size();
-
-    // Reserve space for padding + message
-    shared_buf.reserve(current_size + padding_to_add + message_size);
-
-    // Resize to add the padding bytes
-    shared_buf.resize(current_size + padding_to_add);
-
-    return {&shared_buf};
   }
 
   bool try_to_clear_buffer(bool log_out_of_space);
@@ -297,10 +274,6 @@ class APIConnection : public APIServerConnection {
 
   std::string get_client_combined_info() const { return this->client_info_.get_combined_info(); }
 
-  // Buffer allocator methods for batch processing
-  ProtoWriteBuffer allocate_single_message_buffer(uint16_t size);
-  ProtoWriteBuffer allocate_batch_message_buffer(uint16_t size);
-
  protected:
   // Helper function to handle authentication completion
   void complete_authentication_();