Refactor AsyncFileResponse: remove String _path (#235)

* Refactor AsyncFileResponse: remove String _path

This refactor eliminates the private String _path member from the AsyncFileResponse class, replacing its functionality with a fixed-size char gzPath[MAX_PATH] buffer insife of function.

The use of Arduino's dynamic String class has known drawbacks in memory-constrained or real-time systems, particularly due to heap fragmentation and unpredictable allocation behavior. By switching to a statically allocated C-style buffer, the implementation now benefits from improved memory determinism, reduced fragmentation risk, and overall lower memory overhead.
In addition to reducing memory fragmentation and improving stability in embedded environments, this change also yields better execution speed.
This change maintains behavioral equivalence.

* Change for use arduino String

* Implemented @mathieucarbou's suggestion

Thank you very much for indicating compatibility with other devices.

* Add files via upload

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/WebResponses.cpp

* ci(pre-commit): Apply automatic fixes

---------

Co-authored-by: Mathieu Carbou <mathieu.carbou@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

Author: 4 people

src/WebResponseImpl.h

@@ -75,7 +75,6 @@ class AsyncFileResponse : public AsyncAbstractResponse {
 
 private:
   File _content;
-  String _path;
   void _setContentTypeFromPath(const String &path);
 
 public:

src/WebResponses.cpp

@@ -696,15 +696,19 @@ void AsyncFileResponse::_setContentTypeFromPath(const String &path) {
  */
 AsyncFileResponse::AsyncFileResponse(FS &fs, const String &path, const char *contentType, bool download, AwsTemplateProcessor callback)
   : AsyncAbstractResponse(callback) {
+
   // Try to open the uncompressed version first
   _content = fs.open(path, fs::FileOpenMode::read);
   if (_content.available()) {
-    _path = path;
     _contentLength = _content.size();
   } else {
     // Try to open the compressed version (.gz)
-    _path = path + asyncsrv::T__gz;
-    _content = fs.open(_path, fs::FileOpenMode::read);
+    String gzPath;
+    uint16_t pathLen = path.length();
+    gzPath.reserve(pathLen + 3);
+    gzPath.concat(path);
+    gzPath.concat(asyncsrv::T__gz);
+    _content = fs.open(gzPath, fs::FileOpenMode::read);
     _contentLength = _content.size();
 
     if (_content.seek(_contentLength - 8)) {
@@ -753,7 +757,6 @@ AsyncFileResponse::AsyncFileResponse(FS &fs, const String &path, const char *con
 AsyncFileResponse::AsyncFileResponse(File content, const String &path, const char *contentType, bool download, AwsTemplateProcessor callback)
   : AsyncAbstractResponse(callback) {
   _code = 200;
-  _path = path;
 
   if (!download && String(content.name()).endsWith(T__gz) && !path.endsWith(T__gz)) {
     addHeader(T_Content_Encoding, T_gzip, false);