How send large files with Mongoose with low memory? Send in parts.

ev_handler.c

static void ev_handler(struct mg_connection *nc, int ev, void *p) { 

  if (ev == MG_EV_ACCEPT){
    nc->user_data = Alloc(3 * sizeof(int)); // My malloc implementation
    print("ACCEPT\n",7);
  }
  if (ev == MG_EV_CLOSE){
    AFree(nc->user_data); // Free of malloc implementation
    print("CLOSE\n",6);
  }
  
  if (ev == MG_EV_SEND){
    print("SEND\n",5); // Serial print
    #define CHUNKSIZE MG_MAX_HTTP_SEND_MBUF // max buffer size on each tx

    int file  = ((int *) nc->user_data)[0];
    int *pos = &((int *) nc->user_data)[1];
    int more = ((int *) nc->user_data)[2];

    printf (" %d %d %d \n", file, *pos, more); // printf to serial
  
    if (*pos >= fsFiles[file].size || more == 0) {  // fsFiles: See my gist for this virtualfilesystem code
      nc->flags |= MG_F_SEND_AND_CLOSE;
    } else {
      int size = fsFiles[file].size - *pos;
      if (size > CHUNKSIZE) mg_send (nc,&fsFiles[file].data[*pos], CHUNKSIZE); else mg_send (nc,&fsFiles[file].data[*pos], size); 
      *pos = *pos + CHUNKSIZE;
    }
  }
  
  if (ev == MG_EV_HTTP_REQUEST) {
      int Found = 0;
      int i = 0;
      struct mg_str index = {"/index.html",11};
      struct mg_str *uri = 0;

      print("HTTP\n",5);
      struct http_message *hm = (struct http_message *) p;
      if (mg_vcmp(&hm->uri, "/") == 0) uri = &index; else uri = &hm->uri;
        for (i =0; i < FS_FILES; i++) {
        if (mg_vcmp(uri, fsFiles[i].name) == 0) {
          mg_printf(nc, "HTTP/1.1 200 OK\r\nContent-Type: %s\r\nConnection: close\r\nCache-control: private\r\nServer:  custom\r\n\r\n", fsFiles[i].mime);
          memcpy(nc->user_data, &((int []) {i,0,1}),sizeof(int)*3);
          Found = 1;
          break;
        }
      }

      if (Found == 0) {
        mg_printf(nc, "HTTP/1.1 404 Not Found\r\nConnection: close\r\nCache-control: private\r\nServer:  custom\r\n\r\n");
        memcpy(nc->user_data, ((int []) {1,0,0}),sizeof(int)*3);
        nc->flags |= MG_F_SEND_AND_CLOSE;
      }

  } // http request
} // ev_handler