From a5780eec54ddcfa48d0f34439135bb7dfd08d278 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sat, 7 Mar 2026 15:41:01 -1000
Subject: [PATCH] Extract varint_wide helper to deduplicate cascade

The constexpr path and the noinline slow path shared the same
if/else cascade for values >= 128. Extract into a private
constexpr ESPHOME_ALWAYS_INLINE helper used by both.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 esphome/components/api/proto.cpp | 13 +------------
 esphome/components/api/proto.h   | 25 +++++++++++++++----------
 2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/esphome/components/api/proto.cpp b/esphome/components/api/proto.cpp
index 4f16815d1b..2f51c5c2a6 100644
--- a/esphome/components/api/proto.cpp
+++ b/esphome/components/api/proto.cpp
@@ -8,18 +8,7 @@ namespace esphome::api {
 
 static const char *const TAG = "api.proto";
 
-uint32_t ProtoSize::varint_slow(uint32_t value) {
-  // value is guaranteed >= 128 here (fast path handled inline)
-  if (value < 16384) {
-    return 2;  // 14 bits
-  } else if (value < 2097152) {
-    return 3;  // 21 bits
-  } else if (value < 268435456) {
-    return 4;  // 28 bits
-  } else {
-    return 5;  // 32 bits (maximum for uint32_t)
-  }
-}
+uint32_t ProtoSize::varint_slow(uint32_t value) { return varint_wide(value); }
 
 #ifdef USE_API_VARINT64
 optional<ProtoVarInt> ProtoVarInt::parse_wide(const uint8_t *buffer, uint32_t len, uint32_t *consumed,
diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index ec49964035..10581a7f0a 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -514,21 +514,26 @@ class ProtoSize {
   static constexpr inline uint32_t ESPHOME_ALWAYS_INLINE varint(uint32_t value) {
     if (value < 128)
       return 1;  // Fast path: 7 bits, most common case
-    if (__builtin_is_constant_evaluated()) {
-      // Compile-time: full cascade for constexpr callers
-      if (value < 16384)
-        return 2;
-      if (value < 2097152)
-        return 3;
-      if (value < 268435456)
-        return 4;
-      return 5;
-    }
+    if (__builtin_is_constant_evaluated())
+      return varint_wide(value);
     return varint_slow(value);
   }
   // Slow path for varint >= 128, outlined to keep fast path small
   static uint32_t varint_slow(uint32_t value) __attribute__((noinline));
 
+ private:
+  // Shared cascade for values >= 128 (used by both constexpr and noinline paths)
+  static constexpr inline uint32_t ESPHOME_ALWAYS_INLINE varint_wide(uint32_t value) {
+    if (value < 16384)
+      return 2;
+    if (value < 2097152)
+      return 3;
+    if (value < 268435456)
+      return 4;
+    return 5;
+  }
+
+ public:
   /**
    * @brief Calculates the size in bytes needed to encode a uint64_t value as a varint
    *