move to new skeleton

tutorials/http/huge-response/main.c

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+// Copyright (c) 2021 Cesanta Software Limited
+// All rights reserved
+//
+// Example that demonstrates how to send a large responses with limited memory.
+// We're going to send a JSON array of many integer values, s_data.
+// The idea is to send a response in small chunks, and let the client request
+// the next chunk.
+// Periodically, s_data changes, which is tracked by s_version.
+// Client requests a range and a version, to ensure data integrity.
+//
+//  1. Start this server, type `make`
+//  2. Open http://localhost:8000 in your browser
+
+#include "mongoose.h"
+
+static const char *s_listen_on = "http://localhost:8000";
+static const char *s_root_dir = "web_root";
+
+#define DATA_SIZE 10000        // Total number of elements
+#define CHUNK_SIZE 100         // Max number returned in one API call
+static int s_data[DATA_SIZE];  // Simulate some complex big data
+static long s_version = 0;     // Data "version"
+
+static long getparam(struct mg_http_message *hm, const char *json_path) {
+  double dv = 0;
+  mg_json_get_num(hm->body, json_path, &dv);
+  return dv;
+}
+
+static size_t printdata(mg_pfn_t out, void *ptr, va_list *ap) {
+  unsigned start = va_arg(*ap, unsigned);
+  unsigned max = start + CHUNK_SIZE;
+  const char *comma = "";
+  size_t n = 0;
+  if (max > DATA_SIZE) max = DATA_SIZE;
+  while (start < max) {
+    n += mg_xprintf(out, ptr, "%s%d", comma, s_data[start]);
+    comma = ",";
+    start++;
+  }
+  return n;
+}
+
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_message *hm = ev_data;
+    if (mg_match(hm->uri, mg_str("/api/data"), NULL)) {
+      const char *headers = "content-type: text/json\r\n";
+      long start = getparam(hm, "$.start");
+      long version = getparam(hm, "$.version");
+      MG_DEBUG(("%.*s", (int) hm->body.len, hm->body.buf));
+      if (version > 0 && version != s_version) {
+        // Version mismatch: s_data has changed while client fetches it
+        // Tell client to restart
+        mg_http_reply(c, 200, headers, "{%m:%m, %m:%ld}", MG_ESC("error"),
+                      MG_ESC("wrong version"), MG_ESC("version"), version);
+      } else {
+        // Return data, up to CHUNK_SIZE elements
+        mg_http_reply(c, 200, headers, "{%m:%ld,%m:%ld,%m:[%M]}",
+                      MG_ESC("version"), s_version, MG_ESC("start"), start,
+                      MG_ESC("data"), printdata, start);
+      }
+    } else {
+      struct mg_http_serve_opts opts = {0};
+      opts.root_dir = s_root_dir;
+      mg_http_serve_dir(c, hm, &opts);
+    }
+  }
+}
+
+static void timer_fn(void *arg) {
+  for (int i = 0; i < DATA_SIZE; i++) {
+    s_data[i] = rand();
+  }
+  s_version++;
+  (void) arg;
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  mg_mgr_init(&mgr);
+  srand(time(NULL));
+  mg_timer_add(&mgr, 5000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, NULL);
+  mg_http_listen(&mgr, s_listen_on, fn, NULL);
+  MG_INFO(("Listening on %s", s_listen_on));
+  for (;;) mg_mgr_poll(&mgr, 1000);
+  mg_mgr_free(&mgr);
+  return 0;
+}