Showing the files on an SD card

#21

Is there documentation for the directory function? I remember it exists but can never find it in the documentation. I’d think it would be on the SD card page but maybe its elsewhere?

#22

Yes, I seem to have forgotten that. I’ve added it to the Language reference page and the SD card interface page, and thanks for pointing it out!

#23

I modified the directory function to let you enter an optional path so you can look into folders. In this version it returns a cons pair with the file name and size if its a file and just the name if its a directory but that can be commented out if one wants only filenames.


//change the entry code to 0201 so denote the function can accept one argument
object *fn_directory(object *args, object *env) {
  (void) env;
  char *sd_path_buf = NULL; 

  SDBegin();
  File root; 
  object *result = cons(NULL, NULL);
  object *ptr = result;
  
  if (args != NULL) {
    object *arg1 = checkstring(first(args));
    int len = stringlength(arg1) + 2; //make it longer for the initial slash and the null terminator
    sd_path_buf = (char*)malloc(len); 
    if(sd_path_buf != NULL){
      cstring(arg1, &sd_path_buf[1], len-1);
      sd_path_buf[0] = '/';  //really weird way to concatenate a slash to the front...
      root = SD.open(sd_path_buf);
    } //what if malloc fails? :0
  }
  else{
    root = SD.open("/");
  }

  while (true) {
    File entry =  root.openNextFile();
    if (!entry) break; // no more files
    object *filename = lispstring((char*)entry.name());
    if (entry.isDirectory()) {
      cdr(ptr) = cons(filename, NULL);
    }else{
      cdr(ptr) = cons(cons(filename, number(entry.size())), NULL);
    }
    ptr = cdr(ptr);
    entry.close();
  }
  
  if(sd_path_buf != NULL) free(sd_path_buf);
  root.close();
  return cdr(result);
}

Here’s how it works in practice:

17288> (directory)
(("Greeting.txt" . 18) ("name.txt" . 28) ("name2.txt" . 18) ("tedt1.CL" . 13) "System Volume Information" "example folder")

17902> (directory "example folder")
(("stuff.txt" . 59))

17902> (directory "System Volume Information")
(("IndexerVolumeGuid" . 76) ("WPSettings.dat" . 12))

17902> (directory (nth 5 (directory)))
(("stuff.txt" . 59))

17902> (caar (directory (nth 5 (directory))))
"stuff.txt"