Added LargeResponse example

examples/ChunkResponse/ChunkResponse.ino

@@ -94,7 +94,7 @@ void setup() {
   // first time: serves the file and cache headers
   // curl -N -v http://192.168.4.1/ --output -
   //
-  // secodn time: serves 304
+  // second time: serves 304
   // curl -N -v -H "if-none-match: 4272" http://192.168.4.1/ --output -
   //
   server.on("/", HTTP_GET, [](AsyncWebServerRequest *request) {

examples/LargeResponse/LargeResponse.ino

@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright 2016-2025 Hristo Gochkov, Mathieu Carbou, Emil Muratov
+
+//
+// Example to send a large response and control the filling of the buffer.
+//
+// This is also a MRE for:
+// - https://github.com/ESP32Async/ESPAsyncWebServer/issues/242
+// - https://github.com/ESP32Async/ESPAsyncWebServer/issues/315
+//
+
+#include <Arduino.h>
+#if defined(ESP32) || defined(LIBRETINY)
+#include <AsyncTCP.h>
+#include <WiFi.h>
+#elif defined(ESP8266)
+#include <ESP8266WiFi.h>
+#include <ESPAsyncTCP.h>
+#elif defined(TARGET_RP2040) || defined(TARGET_RP2350) || defined(PICO_RP2040) || defined(PICO_RP2350)
+#include <RPAsyncTCP.h>
+#include <WiFi.h>
+#endif
+
+#include <ESPAsyncWebServer.h>
+
+static AsyncWebServer server(80);
+
+static const size_t totalResponseSize = 16 * 1000;  // 16 KB
+static char fillChar = 'A';
+
+class CustomResponse : public AsyncAbstractResponse {
+public:
+  explicit CustomResponse() {
+    _code = 200;
+    _contentType = "text/plain";
+    _sendContentLength = false;
+  }
+
+  bool _sourceValid() const override {
+    return true;
+  }
+
+  size_t _fillBuffer(uint8_t *buf, size_t buflen) override {
+    if (_sent == RESPONSE_TRY_AGAIN) {
+      Serial.println("Simulating temporary unavailability of data...");
+      _sent = 0;
+      return RESPONSE_TRY_AGAIN;
+    }
+    size_t remaining = totalResponseSize - _sent;
+    if (remaining == 0) {
+      return 0;
+    }
+    if (buflen > remaining) {
+      buflen = remaining;
+    }
+    Serial.printf("Filling '%c' @ sent: %u, buflen: %u\n", fillChar, _sent, buflen);
+    std::fill_n(buf, buflen, static_cast<uint8_t>(fillChar));
+    _sent += buflen;
+    fillChar = (fillChar == 'Z') ? 'A' : fillChar + 1;
+    return buflen;
+  }
+
+private:
+  char fillChar = 'A';
+  size_t _sent = 0;
+};
+
+void setup() {
+  Serial.begin(115200);
+
+#if SOC_WIFI_SUPPORTED || CONFIG_ESP_WIFI_REMOTE_ENABLED || LT_ARD_HAS_WIFI || CONFIG_ESP32_WIFI_ENABLED
+  WiFi.mode(WIFI_AP);
+  WiFi.softAP("esp-captive");
+#endif
+
+  // Example to use a AwsResponseFiller
+  //
+  // curl -v http://192.168.4.1/1 | grep -o '.' | sort | uniq -c
+  //
+  // Should output 16000 and the counts for each character from A to D
+  //
+  // Console:
+  //
+  // Filling 'A' @ index: 0, maxLen: 5652, toSend: 5652
+  // Filling 'B' @ index: 5652, maxLen: 4308, toSend: 4308
+  // Filling 'C' @ index: 9960, maxLen: 2888, toSend: 2888
+  // Filling 'D' @ index: 12848, maxLen: 3152, toSend: 3152
+  //
+  server.on("/1", HTTP_GET, [](AsyncWebServerRequest *request) {
+    fillChar = 'A';
+    AsyncWebServerResponse *response = request->beginResponse("text/plain", totalResponseSize, [](uint8_t *buffer, size_t maxLen, size_t index) -> size_t {
+      size_t remaining = totalResponseSize - index;
+      size_t toSend = (remaining < maxLen) ? remaining : maxLen;
+      Serial.printf("Filling '%c' @ index: %u, maxLen: %u, toSend: %u\n", fillChar, index, maxLen, toSend);
+      std::fill_n(buffer, toSend, static_cast<uint8_t>(fillChar));
+      fillChar = (fillChar == 'Z') ? 'A' : fillChar + 1;
+      return toSend;
+    });
+    request->send(response);
+  });
+
+  // Example to use a AsyncAbstractResponse
+  //
+  // curl -v http://192.168.4.1/2 | grep -o '.' | sort | uniq -c
+  //
+  // Should output 16000
+  //
+  // Console:
+  //
+  // Filling 'A' @ sent: 0, buflen: 5675
+  // Filling 'B' @ sent: 5675, buflen: 4308
+  // Filling 'C' @ sent: 9983, buflen: 5760
+  // Filling 'D' @ sent: 15743, buflen: 257
+  //
+  server.on("/2", HTTP_GET, [](AsyncWebServerRequest *request) {
+    request->send(new CustomResponse());
+  });
+
+  server.begin();
+}
+
+void loop() {
+  delay(100);
+}

platformio.ini

@@ -14,6 +14,7 @@ lib_dir = .
 ; src_dir = examples/FlashResponse
 ; src_dir = examples/HeaderManipulation
 ; src_dir = examples/Json
+; src_dir = examples/LargeResponse
 ; src_dir = examples/Logging
 ; src_dir = examples/MessagePack
 ; src_dir = examples/Middleware