Replace use of LinkedList<T> with std::list for request headers

Based on commit 2183addab047126b5ac259fc5dfffecfb21f60a0 of dumbfixes
branch of 0xFEEDC0DE64 fork of ESPAsyncWebServer.

Step two of removal of homebrewed LinkedList in favor of standard C++
containers. For consistency, the list of interesting headers in the
request has been converted to a std::vector<String>. Also, const
versions of header query functions have been implemented. The original
patch also happens to fix bug #837, and this manual cherry-pick replaces
the previous fix with the dumbfixes one.

src/ESPAsyncWebServer.h

@@ -24,6 +24,7 @@
 #include "Arduino.h"
 
 #include <functional>
+#include <list>
 #include "FS.h"
 
 #include "StringArray.h"
@@ -154,7 +155,7 @@ class AsyncWebServerRequest {
     AsyncWebServer* _server;
     AsyncWebHandler* _handler;
     AsyncWebServerResponse* _response;
-    StringArray _interestingHeaders;
+    std::vector<String> _interestingHeaders;
     ArDisconnectHandler _onDisconnectfn;
 
     String _temp;
@@ -176,7 +177,7 @@ class AsyncWebServerRequest {
     size_t _contentLength;
     size_t _parsedLength;
 
-    LinkedList<AsyncWebHeader *> _headers;
+    std::list<AsyncWebHeader> _headers;
     LinkedList<AsyncWebParameter *> _params;
     LinkedList<String *> _pathParams;
 
@@ -270,9 +271,12 @@ class AsyncWebServerRequest {
     bool hasHeader(const String& name) const;   // check if header exists
     bool hasHeader(const __FlashStringHelper * data) const;   // check if header exists
 
-    AsyncWebHeader* getHeader(const String& name) const;
+    AsyncWebHeader* getHeader(const String& name);
-    AsyncWebHeader* getHeader(const __FlashStringHelper * data) const;
+    const AsyncWebHeader* getHeader(const String& name) const;
-    AsyncWebHeader* getHeader(size_t num) const;
+    AsyncWebHeader* getHeader(const __FlashStringHelper * data);
+    const AsyncWebHeader* getHeader(const __FlashStringHelper * data) const;
+    AsyncWebHeader* getHeader(size_t num);
+    const AsyncWebHeader* getHeader(size_t num) const;
 
     size_t params() const;                      // get arguments count
     bool hasParam(const String& name, bool post=false, bool file=false) const;

src/WebRequest.cpp

@@ -51,7 +51,6 @@ AsyncWebServerRequest::AsyncWebServerRequest(AsyncWebServer* s, AsyncClient* c)
   , _expectingContinue(false)
   , _contentLength(0)
   , _parsedLength(0)
-  , _headers(LinkedList<AsyncWebHeader *>([](AsyncWebHeader *h){ delete h; }))
   , _params(LinkedList<AsyncWebParameter *>([](AsyncWebParameter *p){ delete p; }))
   , _pathParams(LinkedList<String *>([](String *p){ delete p; }))
   , _multiParseState(0)
@@ -76,12 +75,12 @@ AsyncWebServerRequest::AsyncWebServerRequest(AsyncWebServer* s, AsyncClient* c)
 }
 
 AsyncWebServerRequest::~AsyncWebServerRequest(){
-  _headers.free();
+  _headers.clear();
 
   _params.free();
   _pathParams.free();
 
-  _interestingHeaders.free();
+  _interestingHeaders.clear();
 
   if(_response != NULL){
     delete _response;
@@ -182,20 +181,19 @@ void AsyncWebServerRequest::_onData(void *buf, size_t len){
 }
 
 void AsyncWebServerRequest::_removeNotInterestingHeaders(){
-  if (_interestingHeaders.containsIgnoreCase(F("ANY"))) {
+  if (std::any_of(std::begin(_interestingHeaders), std::end(_interestingHeaders),
+      [](const String &str){ return str.equalsIgnoreCase(F("ANY")); }))
       return; // nothing to do
-  }
+
-  // When removing items from the list, we must increase the iterator first
+  for(auto iter = std::begin(_headers); iter != std::end(_headers); )
-  // before removing the current item, otherwise the iterator is invalidated
+  {
-  // So, no for(;;) loop can be used, see: https://stackoverflow.com/q/596162
+      const auto name = iter->name();
-  auto i_header = _headers.begin();
+
-  const auto i_end = _headers.end();
+      if (std::none_of(std::begin(_interestingHeaders), std::end(_interestingHeaders),
-  while (i_header != i_end){
+                       [&name](const String &str){ return str.equalsIgnoreCase(name); }))
-      const auto header = *i_header;
+          iter = _headers.erase(iter);
-      ++i_header;
+      else
-      if(!_interestingHeaders.containsIgnoreCase(header->name().c_str())){
+          iter++;
-        _headers.remove(header);
-      }
   }
 }
 
@@ -370,7 +368,7 @@ bool AsyncWebServerRequest::_parseReqHeader(){
         }
       }
     }
-    _headers.add(new AsyncWebHeader(name, value));
+    _headers.emplace_back(name, value);
   }
   _temp = String();
   return true;
@@ -611,12 +609,12 @@ void AsyncWebServerRequest::_parseLine(){
 }
 
 size_t AsyncWebServerRequest::headers() const{
-  return _headers.length();
+  return _headers.size();
 }
 
 bool AsyncWebServerRequest::hasHeader(const String& name) const {
   for(const auto& h: _headers){
-    if(h->name().equalsIgnoreCase(name)){
+    if(h.name().equalsIgnoreCase(name)){
       return true;
     }
   }
@@ -627,22 +625,64 @@ bool AsyncWebServerRequest::hasHeader(const __FlashStringHelper * data) const {
   return hasHeader(String(data));
 }
 
-AsyncWebHeader* AsyncWebServerRequest::getHeader(const String& name) const {
+AsyncWebHeader* AsyncWebServerRequest::getHeader(const String& name) {
-  for(const auto& h: _headers){
+  auto iter = std::find_if(std::begin(_headers), std::end(_headers),
-    if(h->name().equalsIgnoreCase(name)){
+                           [&name](const AsyncWebHeader &header){ return header.name().equalsIgnoreCase(name); });
-      return h;
+
-    }
+  if (iter == std::end(_headers))
-  }
         return nullptr;
+
+  return &(*iter);
 }
 
-AsyncWebHeader* AsyncWebServerRequest::getHeader(const __FlashStringHelper * data) const {
+const AsyncWebHeader* AsyncWebServerRequest::getHeader(const String& name) const {
-  return getHeader(String(data));
+  auto iter = std::find_if(std::begin(_headers), std::end(_headers),
+                           [&name](const AsyncWebHeader &header){ return header.name().equalsIgnoreCase(name); });
+
+  if (iter == std::end(_headers))
+        return nullptr;
+
+  return &(*iter);
 }
 
-AsyncWebHeader* AsyncWebServerRequest::getHeader(size_t num) const {
+AsyncWebHeader* AsyncWebServerRequest::getHeader(const __FlashStringHelper * data) {
-  auto header = _headers.nth(num);
+  PGM_P p = reinterpret_cast<PGM_P>(data);
-  return header ? *header : nullptr;
+  size_t n = strlen_P(p);
+  char * name = (char*) malloc(n+1);
+  if (name) {
+    strcpy_P(name, p);
+    AsyncWebHeader* result = getHeader( String(name));
+    free(name);
+    return result;
+  } else {
+    return nullptr;
+  }
+}
+
+const AsyncWebHeader* AsyncWebServerRequest::getHeader(const __FlashStringHelper * data) const {
+  PGM_P p = reinterpret_cast<PGM_P>(data);
+  size_t n = strlen_P(p);
+  char * name = (char*) malloc(n+1);
+  if (name) {
+    strcpy_P(name, p);
+    const AsyncWebHeader* result = getHeader( String(name));
+    free(name);
+    return result;
+  } else {
+    return nullptr;
+  }
+}
+
+AsyncWebHeader* AsyncWebServerRequest::getHeader(size_t num) {
+  if (num >= _headers.size())
+      return nullptr;
+  return &(*std::next(std::begin(_headers), num));
+}
+
+const AsyncWebHeader* AsyncWebServerRequest::getHeader(size_t num) const {
+  if (num >= _headers.size())
+      return nullptr;
+  return &(*std::next(std::begin(_headers), num));
 }
 
 size_t AsyncWebServerRequest::params() const {
@@ -681,8 +721,9 @@ AsyncWebParameter* AsyncWebServerRequest::getParam(size_t num) const {
 }
 
 void AsyncWebServerRequest::addInterestingHeader(const String& name){
-  if(!_interestingHeaders.containsIgnoreCase(name))
+  if(std::none_of(std::begin(_interestingHeaders), std::end(_interestingHeaders),
-    _interestingHeaders.add(name);
+                  [&name](const String &str){ return str.equalsIgnoreCase(name); }))
+    _interestingHeaders.push_back(name);
 }
 
 void AsyncWebServerRequest::send(AsyncWebServerResponse *response){
@@ -879,7 +920,7 @@ const String& AsyncWebServerRequest::pathArg(size_t i) const {
 }
 
 const String& AsyncWebServerRequest::header(const char* name) const {
-  AsyncWebHeader* h = getHeader(String(name));
+  const AsyncWebHeader* h = getHeader(String(name));
   return h ? h->value() : emptyString;
 }
 
@@ -889,12 +930,12 @@ const String& AsyncWebServerRequest::header(const __FlashStringHelper * data) co
 
 
 const String& AsyncWebServerRequest::header(size_t i) const {
-  AsyncWebHeader* h = getHeader(i);
+  const AsyncWebHeader* h = getHeader(i);
   return h ?  h->value() : emptyString;
 }
 
 const String& AsyncWebServerRequest::headerName(size_t i) const {
-  AsyncWebHeader* h = getHeader(i);
+  const AsyncWebHeader* h = getHeader(i);
   return h ? h->name() : emptyString;
 }