Replace use of LinkedList<T> with std::list for shared websocket buffers

Based on commit bd4631b of dumbfixes
branch of 0xFEEDC0DE64 fork of ESPAsyncWebServer.

Step one of removal of homebrewed LinkedList in favor of standard C++
containers. Incidentally, this also fixes an analog of bug me-no-dev#837 where
removal of elements while iterating would invalidate the iterator and
lead to memory corruption.

Author: avillacis

src/AsyncWebSocket.cpp

@@ -934,7 +934,6 @@ AsyncWebSocket::AsyncWebSocket(const String& url)
   ,_clients(LinkedList<AsyncWebSocketClient *>([](AsyncWebSocketClient *c){ delete c; }))
   ,_cNextId(1)
   ,_enabled(true)
-  ,_buffers(LinkedList<AsyncWebSocketMessageBuffer *>([](AsyncWebSocketMessageBuffer *b){ delete b; }))
 {
   _eventHandler = NULL;
 }
@@ -1300,22 +1299,23 @@ void AsyncWebSocket::handleRequest(AsyncWebServerRequest *request){
 
 AsyncWebSocketMessageBuffer * AsyncWebSocket::makeBuffer(size_t size)
 {
-  AsyncWebSocketMessageBuffer * buffer = new AsyncWebSocketMessageBuffer(size);
-  if (buffer) {
+  AsyncWebSocketMessageBuffer * buffer{};
+  {
     AsyncWebLockGuard l(_lock);
-    _buffers.add(buffer);
+    _buffers.emplace_back(size);
+    buffer = &_buffers.back();
   }
   return buffer;
 }
 
 AsyncWebSocketMessageBuffer * AsyncWebSocket::makeBuffer(uint8_t * data, size_t size)
 {
-  AsyncWebSocketMessageBuffer * buffer = new AsyncWebSocketMessageBuffer(data, size);
+  AsyncWebSocketMessageBuffer * buffer{};
 
-  if (buffer) {
+  {
     AsyncWebLockGuard l(_lock);
-    // Serial.printf("Add to global buffers = %u\n", _buffers.length() + 1);
-    _buffers.add(buffer);
+    _buffers.emplace_back(data, size);
+    buffer = &_buffers.back();
   }
 
   return buffer;
@@ -1324,11 +1324,12 @@ AsyncWebSocketMessageBuffer * AsyncWebSocket::makeBuffer(uint8_t * data, size_t
 void AsyncWebSocket::_cleanBuffers()
 {
   AsyncWebLockGuard l(_lock);
-  for(AsyncWebSocketMessageBuffer * c: _buffers){
-    if(c && c->canDelete()){
-        // Serial.printf("Remove from global buffers = %u\n", _buffers.length() - 1);
-        _buffers.remove(c);
-    }
+
+  for (auto iter = std::begin(_buffers); iter != std::end(_buffers);){
+    if(iter->canDelete()){
+        iter = _buffers.erase(iter);
+    } else
+        iter++;
   }
 }
 

src/AsyncWebSocket.h

@@ -33,6 +33,8 @@
 
 #include "AsyncWebSynchronization.h"
 
+#include <list>
+
 #ifdef ESP8266
 #include <Hash.h>
 #ifdef CRYPTO_HASH_h // include Hash.h from espressif framework if the first include was from the crypto library
@@ -337,7 +339,7 @@ class AsyncWebSocket: public AsyncWebHandler {
     //  messagebuffer functions/objects.
     AsyncWebSocketMessageBuffer * makeBuffer(size_t size = 0);
     AsyncWebSocketMessageBuffer * makeBuffer(uint8_t * data, size_t size);
-    LinkedList<AsyncWebSocketMessageBuffer *> _buffers;
+    std::list<AsyncWebSocketMessageBuffer> _buffers;
     void _cleanBuffers();
 
     AsyncWebSocketClientLinkedList getClients() const;