[core] Add str_endswith_ignore_case to avoid heap allocation in audio file type detection (#13313)

esphome/components/audio/audio_reader.cpp

@@ -185,18 +185,16 @@ esp_err_t AudioReader::start(const std::string &uri, AudioFileType &file_type) {
       return err;
     }
 
-    std::string url_string = str_lower_case(url);
+    if (str_endswith_ignore_case(url, ".wav")) {
-
-    if (str_endswith(url_string, ".wav")) {
       file_type = AudioFileType::WAV;
     }
 #ifdef USE_AUDIO_MP3_SUPPORT
-    else if (str_endswith(url_string, ".mp3")) {
+    else if (str_endswith_ignore_case(url, ".mp3")) {
       file_type = AudioFileType::MP3;
     }
 #endif
 #ifdef USE_AUDIO_FLAC_SUPPORT
-    else if (str_endswith(url_string, ".flac")) {
+    else if (str_endswith_ignore_case(url, ".flac")) {
       file_type = AudioFileType::FLAC;
     }
 #endif

esphome/core/helpers.cpp

@@ -174,6 +174,13 @@ bool str_endswith(const std::string &str, const std::string &end) {
   return str.rfind(end) == (str.size() - end.size());
 }
 #endif
+
+bool str_endswith_ignore_case(const char *str, size_t str_len, const char *suffix, size_t suffix_len) {
+  if (suffix_len > str_len)
+    return false;
+  return strncasecmp(str + str_len - suffix_len, suffix, suffix_len) == 0;
+}
+
 std::string str_truncate(const std::string &str, size_t length) {
   return str.length() > length ? str.substr(0, length) : str;
 }

esphome/core/helpers.h

@@ -545,6 +545,15 @@ bool str_startswith(const std::string &str, const std::string &start);
 /// Check whether a string ends with a value.
 bool str_endswith(const std::string &str, const std::string &end);
 
+/// Case-insensitive check if string ends with suffix (no heap allocation).
+bool str_endswith_ignore_case(const char *str, size_t str_len, const char *suffix, size_t suffix_len);
+inline bool str_endswith_ignore_case(const char *str, const char *suffix) {
+  return str_endswith_ignore_case(str, strlen(str), suffix, strlen(suffix));
+}
+inline bool str_endswith_ignore_case(const std::string &str, const char *suffix) {
+  return str_endswith_ignore_case(str.c_str(), str.size(), suffix, strlen(suffix));
+}
+
 /// Truncate a string to a specific length.
 /// @warning Allocates heap memory. Avoid in new code - causes heap fragmentation on long-running devices.
 std::string str_truncate(const std::string &str, size_t length);