From 2646ec166baf88fe4ccff5f3896c025d4dcee800 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Thu, 15 May 2025 03:24:47 -0500
Subject: [PATCH] save some bytes

---
 esphome/components/api/api_frame_helper.cpp | 5 +++--
 esphome/components/api/api_frame_helper.h   | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/esphome/components/api/api_frame_helper.cpp b/esphome/components/api/api_frame_helper.cpp
index 82ebd531f6..2d9bed2174 100644
--- a/esphome/components/api/api_frame_helper.cpp
+++ b/esphome/components/api/api_frame_helper.cpp
@@ -185,9 +185,10 @@ APIError APIFrameHelper::try_send_tx_buf_() {
     } else if (sent == 0) {
       // Nothing sent but not an error
       return APIError::WOULD_BLOCK;
-    } else if (static_cast<size_t>(sent) < front_buffer.remaining()) {
+    } else if (static_cast<uint16_t>(sent) < front_buffer.remaining()) {
       // Partially sent, update offset
-      front_buffer.offset += sent;
+      // Cast to ensure no overflow issues with uint16_t
+      front_buffer.offset += static_cast<uint16_t>(sent);
       return APIError::WOULD_BLOCK;  // Stop processing more buffers if we couldn't send a complete buffer
     } else {
       // Buffer completely sent, remove it from the queue
diff --git a/esphome/components/api/api_frame_helper.h b/esphome/components/api/api_frame_helper.h
index 15d9d8664d..f711b091cb 100644
--- a/esphome/components/api/api_frame_helper.h
+++ b/esphome/components/api/api_frame_helper.h
@@ -121,9 +121,10 @@ class APIFrameHelper {
   // Buffer containing data to be sent
   struct SendBuffer {
     std::vector<uint8_t> data;
-    size_t offset{0};  // Current offset within the buffer
+    uint16_t offset{0};  // Current offset within the buffer (uint16_t to reduce memory usage)
 
-    size_t remaining() const { return data.size() - offset; }
+    // Using uint16_t reduces memory usage since ESPHome API messages are limited to 64KB max
+    uint16_t remaining() const { return static_cast<uint16_t>(data.size()) - offset; }
     const uint8_t *current_data() const { return data.data() + offset; }
   };