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78 lines
2.7 KiB
ReStructuredText
78 lines
2.7 KiB
ReStructuredText
.. _libs_filesystem:
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======================
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File System Interfaces
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======================
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LVGL has a :ref:`overview_file_system` module
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to provide an abstraction layer for various file system drivers.
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LVG has built in support for:
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- `FATFS <http://elm-chan.org/fsw/ff/00index_e.html>`__
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- STDIO (Linux and Windows using C standard function .e.g ``fopen``, ``fread``)
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- POSIX (Linux and Windows using POSIX function .e.g ``open``, ``read``)
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- WIN32 (Windows using Win32 API function .e.g ``CreateFileA``, ``ReadFile``)
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- MEMFS (read a file from a memory buffer)
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- LITTLEFS (a little fail-safe filesystem designed for microcontrollers)
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- Arduino ESP LITTLEFS (a little fail-safe filesystem designed for Arduino ESP)
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- Arduino SD (allows for reading from and writing to SD cards)
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You still need to provide the drivers and libraries, this extension
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provides only the bridge between FATFS, STDIO, POSIX, WIN32 and LVGL.
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.. _libs_filesystem_usage:
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Usage
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*****
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In ``lv_conf.h`` enable ``LV_USE_FS_...`` and assign an upper cased
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letter to ``LV_FS_..._LETTER`` (e.g. ``'S'``). After that you can access
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files using that driver letter. E.g. ``"S:path/to/file.txt"``.
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Working with common prefixes
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""""""""""""""""""""""""""""
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A **default driver letter** can be set by ``LV_FS_DEFAULT_DRIVE_LETTER``,
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which allows skipping the drive prefix in file paths.
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For example if ``LV_FS_DEFAULT_DRIVE_LETTER`` is set the ``'S'`` *"path/to/file.txt"* will mean *"S:path/to/file.txt"*.
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This feature is useful if you have only a single driver and don't want to bother with LVGL's driver layer in the file paths.
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It also helps to use a unified path with LVGL's file system and normal file systems.
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The original mechanism is not affected, so a path starting with drive letter will still work.
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The **working directory** can be set with ``LV_FS_..._PATH``. E.g.
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``"/home/joe/projects/"`` The actual file/directory paths will be
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appended to it, allowing to skip the common part.
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Caching
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"""""""
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:ref:`Cached reading <overview_file_system_cache>` is also supported if ``LV_FS_..._CACHE_SIZE`` is set to
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not ``0`` value. :cpp:func:`lv_fs_read` caches this size of data to lower the
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number of actual reads from the storage.
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To use the memory-mapped file emulation an ``lv_fs_path_ex_t`` object must be
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created and initialized. This object can be passed to :cpp:func:`lv_fs_open` as
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the file name:
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.. code-block:: c
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lv_fs_path_ex_t mempath;
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lv_fs_file_t file;
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uint8_t *buffer;
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uint32_t size;
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/* Initialize buffer */
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...
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lv_fs_make_path_from_buffer(&mempath, LV_FS_MEMFS_LETTER, (void*)buffer, size);
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lv_fs_res_t res = lv_fs_open(&file, (const char *)&mempath, LV_FS_MODE_RD);
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.. _libs_filesystem_api:
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API
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***
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