Add optional support for CORS headers (#2688)

* add support for CORS headers

* remove accidental function impl

* rename setCORS to enableCORS, and add aliased function enableCrossOrigin

libraries/WebServer/src/WebServer.cpp

@@ -55,6 +55,7 @@ WebServer::WebServer(IPAddress addr, int port)
 , _currentHeaders(nullptr)
 , _contentLength(0)
 , _chunked(false)
+, _corsEnabled(false)
 {
 }
 
@@ -75,6 +76,7 @@ WebServer::WebServer(int port)
 , _currentHeaders(nullptr)
 , _contentLength(0)
 , _chunked(false)
+, _corsEnabled(false)
 {
 }
 
@@ -366,6 +368,14 @@ void WebServer::setContentLength(const size_t contentLength) {
     _contentLength = contentLength;
 }
 
+void WebServer::enableCORS(boolean value) {
+  _corsEnabled = value;
+}
+
+void WebServer::enableCrossOrigin(boolean value) {
+  enableCORS(value);
+}
+
 void WebServer::_prepareHeader(String& response, int code, const char* content_type, size_t contentLength) {
     response = String(F("HTTP/1.")) + String(_currentVersion) + ' ';
     response += String(code);
@@ -388,6 +398,9 @@ void WebServer::_prepareHeader(String& response, int code, const char* content_t
       sendHeader(String(F("Accept-Ranges")),String(F("none")));
       sendHeader(String(F("Transfer-Encoding")),String(F("chunked")));
     }
+    if (_corsEnabled) {
+        sendHeader(String(FPSTR("Access-Control-Allow-Origin")), String("*"));
+    }
     sendHeader(String(F("Connection")), String(F("close")));
 
     response += _responseHeaders;

libraries/WebServer/src/WebServer.h

@@ -122,6 +122,9 @@ public:
   void send_P(int code, PGM_P content_type, PGM_P content);
   void send_P(int code, PGM_P content_type, PGM_P content, size_t contentLength);
 
+  void enableCORS(boolean value = true);
+  void enableCrossOrigin(boolean value = true);
+
   void setContentLength(const size_t contentLength);
   void sendHeader(const String& name, const String& value, bool first = false);
   void sendContent(const String& content);
@@ -163,6 +166,7 @@ protected:
     String value;
   };
 
+  boolean     _corsEnabled;
   WiFiServer  _server;
 
   WiFiClient  _currentClient;