SDWebserver.ino example produces invalid json and is dog-slow

[sunnyhighway]

printDirectory() in the SDWebserver.ino example produces invalid json.

When a directory contains no files or directories, printDirectory produces only the end of array marker:

]

Better to produce an empty array:

[]

server.sendContent() appears to be dog-slow.
server.send() is faster by at least 1 second.

Proposal:

void printDirectory() {
  if(!server.hasArg("dir")) return returnFail("BAD ARGS");
  String path = server.arg("dir");
  if(path != "/" && !SD.exists((char *)path.c_str())) return returnFail("BAD PATH");
  File dir = SD.open((char *)path.c_str());
  path = String();
  if(!dir.isDirectory()){
    dir.close();
    return returnFail("NOT DIR");
  }
  dir.rewindDirectory();
  WiFiClient client = server.client();

  String output = "[";
  for (int cnt = 0; true; ++cnt) {
    File entry = dir.openNextFile();
    if (!entry)
    break;

    if (cnt > 0) 
      output += ',';

    output += "{\"type\":\"";
    output += (entry.isDirectory()) ? "dir" : "file";
    output += "\",\"name\":\"";
    output += entry.name();
    output += "\"";
    output += "}";
    entry.close();
  }

  output += "]";
  server.send(200, "text/json", output);
  dir.close();
}

[me-no-dev]

#406

what you suggest will break if folder has many files and content get's large.