Close #77: Allow modification of hardcoded headers

examples/SimpleServer/SimpleServer.ino

@@ -61,6 +61,27 @@ void setup() {
     request->send(LittleFS, "/index.html");
   });
 
+  /*
+    ❯ curl -I -X HEAD http://192.168.4.1/download
+    HTTP/1.1 200 OK
+    Content-Length: 1024
+    Content-Type: application/octet-stream
+    Connection: close
+    Accept-Ranges: bytes
+  */
+ // Ref: https://github.com/mathieucarbou/ESPAsyncWebServer/pull/80
+  server.on("/download", HTTP_HEAD | HTTP_GET, [](AsyncWebServerRequest* request) {
+    if (request->method() == HTTP_HEAD) {
+      AsyncWebServerResponse* response = request->beginResponse(200, "application/octet-stream");
+      response->setContentLength(1024); // myFile.getSize()
+      response->addHeader("Accept-Ranges", "bytes");
+      // ...
+      request->send(response);
+    } else {
+      // ...
+    }
+  });
+
   // Send a GET request to <IP>/get?message=<message>
   server.on("/get", HTTP_GET, [](AsyncWebServerRequest* request) {
     String message;

src/ESPAsyncWebServer.h

@@ -581,8 +581,9 @@ class AsyncWebServerResponse {
     virtual void setContentLength(size_t len);
     void setContentType(const String& type) { setContentType(type.c_str()); }
     virtual void setContentType(const char* type);
-    virtual void addHeader(const char* name, const char* value);
-    void addHeader(const String& name, const String& value) { addHeader(name.c_str(), value.c_str()); }
+    virtual bool addHeader(const char* name, const char* value, bool replaceExisting = true);
+    bool addHeader(const String& name, const String& value, bool replaceExisting = true) { return addHeader(name.c_str(), value.c_str(), replaceExisting); }
+    virtual bool removeHeader(const char* name);
     virtual String _assembleHead(uint8_t version);
     virtual bool _started() const;
     virtual bool _finished() const;

src/WebResponses.cpp

@@ -239,18 +239,43 @@ void AsyncWebServerResponse::setContentType(const char* type) {
     _contentType = type;
 }
 
-void AsyncWebServerResponse::addHeader(const char* name, const char* value) {
+bool AsyncWebServerResponse::removeHeader(const char* name) {
+  for (auto i = _headers.begin(); i != _headers.end(); ++i) {
+    if (i->name().equalsIgnoreCase(name)) {
+      _headers.erase(i);
+      return true;
+    }
+  }
+  return false;
+}
+
+bool AsyncWebServerResponse::addHeader(const char* name, const char* value, bool replaceExisting) {
+  for (auto i = _headers.begin(); i != _headers.end(); ++i) {
+    if (i->name().equalsIgnoreCase(name)) {
+      // header already set
+      if (replaceExisting) {
+        // remove, break and add the new one
+        _headers.erase(i);
+        break;
+      } else {
+        // do not update
+        return false;
+      }
+    }
+  }
+  // header was not found found, or existing one was removed
   _headers.emplace_back(name, value);
+  return true;
 }
 
 String AsyncWebServerResponse::_assembleHead(uint8_t version) {
   if (version) {
-    addHeader(T_Accept_Ranges, T_none);
+    addHeader(T_Accept_Ranges, T_none, false);
     if (_chunked)
-      addHeader(Transfer_Encoding, T_chunked);
+      addHeader(T_Transfer_Encoding, T_chunked, false);
   }
   String out;
-  int bufSize = 300;
+  constexpr size_t bufSize = 300;
   char buf[bufSize];
 
 #ifndef ESP8266
@@ -307,7 +332,7 @@ AsyncBasicResponse::AsyncBasicResponse(int code, const char* contentType, const
     if (!_contentType.length())
       _contentType = T_text_plain;
   }
-  addHeader(T_Connection, T_close);
+  addHeader(T_Connection, T_close, false);
 }
 
 void AsyncBasicResponse::_respond(AsyncWebServerRequest* request) {
@@ -385,7 +410,7 @@ AsyncAbstractResponse::AsyncAbstractResponse(AwsTemplateProcessor callback) : _c
 }
 
 void AsyncAbstractResponse::_respond(AsyncWebServerRequest* request) {
-  addHeader(T_Connection, T_close);
+  addHeader(T_Connection, T_close, false);
   _head = _assembleHead(request->version());
   _state = RESPONSE_HEADERS;
   _ack(request, 0, 0);
@@ -663,7 +688,7 @@ AsyncFileResponse::AsyncFileResponse(FS& fs, const String& path, const char* con
 
   if (!download && !fs.exists(_path) && fs.exists(_path + T__gz)) {
     _path = _path + T__gz;
-    addHeader(T_Content_Encoding, T_gzip);
+    addHeader(T_Content_Encoding, T_gzip, false);
     _callback = nullptr; // Unable to process zipped templates
     _sendContentLength = true;
     _chunked = false;
@@ -688,7 +713,7 @@ AsyncFileResponse::AsyncFileResponse(FS& fs, const String& path, const char* con
     // set filename and force rendering
     snprintf_P(buf, sizeof(buf), PSTR("inline"));
   }
-  addHeader(T_Content_Disposition, buf);
+  addHeader(T_Content_Disposition, buf, false);
 }
 
 AsyncFileResponse::AsyncFileResponse(File content, const String& path, const char* contentType, bool download, AwsTemplateProcessor callback) : AsyncAbstractResponse(callback) {
@@ -696,7 +721,7 @@ AsyncFileResponse::AsyncFileResponse(File content, const String& path, const cha
   _path = path;
 
   if (!download && String(content.name()).endsWith(T__gz) && !path.endsWith(T__gz)) {
-    addHeader(T_Content_Encoding, T_gzip);
+    addHeader(T_Content_Encoding, T_gzip, false);
     _callback = nullptr; // Unable to process gzipped templates
     _sendContentLength = true;
     _chunked = false;
@@ -719,7 +744,7 @@ AsyncFileResponse::AsyncFileResponse(File content, const String& path, const cha
   } else {
     snprintf_P(buf, sizeof(buf), PSTR("inline"));
   }
-  addHeader(T_Content_Disposition, buf);
+  addHeader(T_Content_Disposition, buf, false);
 }
 
 size_t AsyncFileResponse::_fillBuffer(uint8_t* data, size_t len) {

src/literals.h

@@ -41,7 +41,7 @@ static constexpr const char* T_none             = "none";
 static constexpr const char* T_UPGRADE          = "Upgrade";
 static constexpr const char* T_WS               = "websocket";
 static constexpr const char* T_WWW_AUTH         = "WWW-Authenticate";
-static constexpr const char* Transfer_Encoding  = "Transfer-Encoding";
+static constexpr const char* T_Transfer_Encoding = "Transfer-Encoding";
 
 // HTTP Methods
 static constexpr const char* T_ANY      = "ANY";
@@ -210,7 +210,7 @@ static const char T_none[] PROGMEM = "none";
 static const char T_UPGRADE[] PROGMEM = "Upgrade";
 static const char T_WS[] PROGMEM = "websocket";
 static const char T_WWW_AUTH[] PROGMEM = "WWW-Authenticate";
-static const char Transfer_Encoding[] PROGMEM = "Transfer-Encoding";
+static const char T_Transfer_Encoding[] PROGMEM = "Transfer-Encoding";
 
 // HTTP Methods
 static const char T_ANY[] PROGMEM = "ANY";