From 0990a9c2b0515ce46f7fb477d64615409309885e Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 5 Jan 2026 07:39:24 -1000
Subject: [PATCH] [esp32_ble] Avoid heap allocation in ESPBTUUID::from_raw for
 string literals (#12980)

---
 esphome/components/alpha3/alpha3.h        |  6 ++---
 esphome/components/esp32_ble/ble_uuid.cpp | 28 +++++++++++------------
 esphome/components/esp32_ble/ble_uuid.h   |  8 ++++++-
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/esphome/components/alpha3/alpha3.h b/esphome/components/alpha3/alpha3.h
index 7189ecbc33..19d8e99331 100644
--- a/esphome/components/alpha3/alpha3.h
+++ b/esphome/components/alpha3/alpha3.h
@@ -15,10 +15,8 @@ namespace alpha3 {
 namespace espbt = esphome::esp32_ble_tracker;
 
 static const espbt::ESPBTUUID ALPHA3_GENI_SERVICE_UUID = espbt::ESPBTUUID::from_uint16(0xfe5d);
-static const espbt::ESPBTUUID ALPHA3_GENI_CHARACTERISTIC_UUID =
-    espbt::ESPBTUUID::from_raw({static_cast<char>(0xa9), 0x7b, static_cast<char>(0xb8), static_cast<char>(0x85), 0x0,
-                                0x1a, 0x28, static_cast<char>(0xaa), 0x2a, 0x43, 0x6e, 0x3, static_cast<char>(0xd1),
-                                static_cast<char>(0xff), static_cast<char>(0x9c), static_cast<char>(0x85)});
+static const espbt::ESPBTUUID ALPHA3_GENI_CHARACTERISTIC_UUID = espbt::ESPBTUUID::from_raw(
+    {0xa9, 0x7b, 0xb8, 0x85, 0x00, 0x1a, 0x28, 0xaa, 0x2a, 0x43, 0x6e, 0x03, 0xd1, 0xff, 0x9c, 0x85});
 static const int16_t GENI_RESPONSE_HEADER_LENGTH = 13;
 static const size_t GENI_RESPONSE_TYPE_LENGTH = 8;
 
diff --git a/esphome/components/esp32_ble/ble_uuid.cpp b/esphome/components/esp32_ble/ble_uuid.cpp
index c6b27f3bb9..7bad8d1866 100644
--- a/esphome/components/esp32_ble/ble_uuid.cpp
+++ b/esphome/components/esp32_ble/ble_uuid.cpp
@@ -39,36 +39,36 @@ ESPBTUUID ESPBTUUID::from_raw_reversed(const uint8_t *data) {
     ret.uuid_.uuid.uuid128[ESP_UUID_LEN_128 - 1 - i] = data[i];
   return ret;
 }
-ESPBTUUID ESPBTUUID::from_raw(const std::string &data) {
+ESPBTUUID ESPBTUUID::from_raw(const char *data, size_t length) {
   ESPBTUUID ret;
-  if (data.length() == 4) {
+  if (length == 4) {
     // 16-bit UUID as 4-character hex string
-    auto parsed = parse_hex<uint16_t>(data);
+    auto parsed = parse_hex<uint16_t>(data, length);
     if (parsed.has_value()) {
       ret.uuid_.len = ESP_UUID_LEN_16;
       ret.uuid_.uuid.uuid16 = parsed.value();
     }
-  } else if (data.length() == 8) {
+  } else if (length == 8) {
     // 32-bit UUID as 8-character hex string
-    auto parsed = parse_hex<uint32_t>(data);
+    auto parsed = parse_hex<uint32_t>(data, length);
     if (parsed.has_value()) {
       ret.uuid_.len = ESP_UUID_LEN_32;
       ret.uuid_.uuid.uuid32 = parsed.value();
     }
-  } else if (data.length() == 16) {  // how we can have 16 byte length string reprezenting 128 bit uuid??? needs to be
-                                     // investigated (lack of time)
+  } else if (length == 16) {  // how we can have 16 byte length string reprezenting 128 bit uuid??? needs to be
+                              // investigated (lack of time)
     ret.uuid_.len = ESP_UUID_LEN_128;
-    memcpy(ret.uuid_.uuid.uuid128, (uint8_t *) data.data(), 16);
-  } else if (data.length() == 36) {
+    memcpy(ret.uuid_.uuid.uuid128, reinterpret_cast<const uint8_t *>(data), 16);
+  } else if (length == 36) {
     // If the length of the string is 36 bytes then we will assume it is a long hex string in
     // UUID format.
     ret.uuid_.len = ESP_UUID_LEN_128;
     int n = 0;
-    for (uint i = 0; i < data.length(); i += 2) {
-      if (data.c_str()[i] == '-')
+    for (size_t i = 0; i < length; i += 2) {
+      if (data[i] == '-')
         i++;
-      uint8_t msb = data.c_str()[i];
-      uint8_t lsb = data.c_str()[i + 1];
+      uint8_t msb = data[i];
+      uint8_t lsb = data[i + 1];
 
       if (msb > '9')
         msb -= 7;
@@ -77,7 +77,7 @@ ESPBTUUID ESPBTUUID::from_raw(const std::string &data) {
       ret.uuid_.uuid.uuid128[15 - n++] = ((msb & 0x0F) << 4) | (lsb & 0x0F);
     }
   } else {
-    ESP_LOGE(TAG, "ERROR: UUID value not 2, 4, 16 or 36 bytes - %s", data.c_str());
+    ESP_LOGE(TAG, "ERROR: UUID value not 2, 4, 16 or 36 bytes - %s", data);
   }
   return ret;
 }
diff --git a/esphome/components/esp32_ble/ble_uuid.h b/esphome/components/esp32_ble/ble_uuid.h
index ed561d70e4..2d8c69e44e 100644
--- a/esphome/components/esp32_ble/ble_uuid.h
+++ b/esphome/components/esp32_ble/ble_uuid.h
@@ -7,6 +7,7 @@
 #ifdef USE_ESP32
 #ifdef USE_ESP32_BLE_UUID
 
+#include <initializer_list>
 #include <span>
 #include <string>
 #include <esp_bt_defs.h>
@@ -27,7 +28,12 @@ class ESPBTUUID {
   static ESPBTUUID from_raw(const uint8_t *data);
   static ESPBTUUID from_raw_reversed(const uint8_t *data);
 
-  static ESPBTUUID from_raw(const std::string &data);
+  static ESPBTUUID from_raw(const char *data, size_t length);
+  static ESPBTUUID from_raw(const char *data) { return from_raw(data, strlen(data)); }
+  static ESPBTUUID from_raw(const std::string &data) { return from_raw(data.c_str(), data.length()); }
+  static ESPBTUUID from_raw(std::initializer_list<uint8_t> data) {
+    return from_raw(reinterpret_cast<const char *>(data.begin()), data.size());
+  }
 
   static ESPBTUUID from_uuid(esp_bt_uuid_t uuid);