======================
File System Interfaces
======================

LVGL has a :ref:`file-system` module
to provide an abstraction layer for various file system drivers.

LVG has built in support for:

- `FATFS <http://elm-chan.org/fsw/ff/00index_e.html>`__
- STDIO (Linux and Windows using C standard function .e.g fopen, fread)
- POSIX (Linux and Windows using POSIX function .e.g open, read)
- WIN32 (Windows using Win32 API function .e.g CreateFileA, ReadFile)
- MEMFS (read a file from a memory buffer)

You still need to provide the drivers and libraries, this extension
provides only the bridge between FATFS, STDIO, POSIX, WIN32 and LVGL.

Usage
*****

In ``lv_conf.h`` enable ``LV_USE_FS_...`` and assign an upper cased
letter to ``LV_FS_..._LETTER`` (e.g. ``'S'``). After that you can access
files using that driver letter. E.g. ``"S:path/to/file.txt"``.

The work directory can be set with ``LV_FS_..._PATH``. E.g.
``"/home/joe/projects/"`` The actual file/directory paths will be
appended to it.

Cached reading is also supported if ``LV_FS_..._CACHE_SIZE`` is set to
not ``0`` value. :c:func:`lv_fs_read` caches this size of data to lower the
number of actual reads from the storage.

To use the memory-mapped file emulation an ``lv_fs_path_ex_t`` object must be
created and initialized. This object can be passed to :c:func:`lv_fs_open()` as
the file name:

.. code:: c

  lv_fs_path_ex_t mempath;
  lv_fs_file_t file;
  uint8_t *buffer;
  uint32_t size;

  /*Initialize buffer*/
  ...

  lv_fs_make_path_from_buffer(&mempath, LV_FS_MEMFS_LETTER, (void*)buffer, size);
  lv_fs_res_t res = lv_fs_open(&file, (const char *)&mempath, LV_FS_MODE_RD);

API
***