text: /**
   * @file lv_fs.h
   *
   */
  
  #ifndef LV_FS_H
  #define LV_FS_H
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /*********************
   *      INCLUDES
   *********************/
  #include "lv_conf.h"
  
  #if USE_LV_FILESYSTEM
  
  #include <stdint.h>
  #include <stdbool.h>
  #include "lv_mem.h"
  
  /*********************
   *      DEFINES
   *********************/
  #define LV_FS_MAX_FN_LENGTH  64
  
  /**********************
   *      TYPEDEFS
   **********************/
  enum
  {
      LV_FS_RES_OK = 0,
      LV_FS_RES_HW_ERR,      /*Low level hardware error*/
      LV_FS_RES_FS_ERR,      /*Error in the file system structure */
      LV_FS_RES_NOT_EX,      /*Driver, file or directory is not exists*/
      LV_FS_RES_FULL,        /*Disk full*/
      LV_FS_RES_LOCKED,      /*The file is already opened*/
      LV_FS_RES_DENIED,      /*Access denied. Check 'fs_open' modes and write protect*/
      LV_FS_RES_BUSY,        /*The file system now can't handle it, try later*/
      LV_FS_RES_TOUT,        /*Process time outed*/
      LV_FS_RES_NOT_IMP,     /*Requested function is not implemented*/
      LV_FS_RES_OUT_OF_MEM,  /*Not enough memory for an internal operation*/
      LV_FS_RES_INV_PARAM,   /*Invalid parameter among arguments*/
      LV_FS_RES_UNKNOWN,     /*Other unknown error*/
  };
  typedef uint8_t lv_fs_res_t;
  
  struct __lv_fs_drv_t;
  
  typedef struct
  {
      void * file_d;
      struct __lv_fs_drv_t* drv;
  } lv_fs_file_t;
  
  
  typedef struct
  {
      void * dir_d;
      struct __lv_fs_drv_t * drv;
  } lv_fs_dir_t;
  
  enum
  {
      LV_FS_MODE_WR = 0x01,
      LV_FS_MODE_RD = 0x02,
  };
  typedef uint8_t lv_fs_mode_t;
  
  typedef struct __lv_fs_drv_t
  {
      char letter;
      uint16_t file_size;
      uint16_t rddir_size;
      bool (*ready) (void);
  
      lv_fs_res_t (*open) (void * file_p, const char * path, lv_fs_mode_t mode);
      lv_fs_res_t (*close) (void * file_p);
      lv_fs_res_t (*remove) (const char * fn);
      lv_fs_res_t (*read) (void * file_p, void * buf, uint32_t btr, uint32_t * br);
      lv_fs_res_t (*write) (void * file_p, const void * buf, uint32_t btw, uint32_t * bw);
      lv_fs_res_t (*seek) (void * file_p, uint32_t pos);
      lv_fs_res_t (*tell) (void * file_p, uint32_t * pos_p);
      lv_fs_res_t (*trunc) (void * file_p);
      lv_fs_res_t (*size) (void * file_p, uint32_t * size_p);
      lv_fs_res_t (*rename) (const char * oldname, const char * newname);
      lv_fs_res_t (*free) (uint32_t * total_p, uint32_t * free_p);
  
      lv_fs_res_t (*dir_open) (void * rddir_p, const char * path);
      lv_fs_res_t (*dir_read) (void * rddir_p, char * fn);
      lv_fs_res_t (*dir_close) (void * rddir_p);
  } lv_fs_drv_t;
  
  /**********************
   * GLOBAL PROTOTYPES
   **********************/
  
  /**
   * Initialize the File system interface
   */
  void lv_fs_init(void);
  
  /**
   * Add a new drive
   * @param drv_p pointer to an lv_fs_drv_t structure which is inited with the
   * corresponding function pointers. The data will be copied so the variable can be local.
   */
  void lv_fs_add_drv(lv_fs_drv_t * drv_p);
  
  /**
   * Open a file
   * @param file_p pointer to a lv_fs_file_t variable
   * @param path path to the file beginning with the driver letter (e.g. S:/folder/file.txt)
   * @param mode read: FS_MODE_RD, write: FS_MODE_WR, both: FS_MODE_RD | FS_MODE_WR
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_open (lv_fs_file_t * file_p, const char * path, lv_fs_mode_t mode);
  
  /**
   * Close an already opened file
   * @param file_p pointer to a lv_fs_file_t variable
   * @return  LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_close (lv_fs_file_t * file_p);
  
  /**
   * Delete a file
   * @param path path of the file to delete
   * @return  LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_remove (const char * path);
  
  /**
   * Read from a file
   * @param file_p pointer to a lv_fs_file_t variable
   * @param buf pointer to a buffer where the read bytes are stored
   * @param btr Bytes To Read
   * @param br the number of real read bytes (Bytes Read). NULL if unused.
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_read (lv_fs_file_t * file_p, void * buf, uint32_t btr, uint32_t * br);
  
  /**
   * Write into a file
   * @param file_p pointer to a lv_fs_file_t variable
   * @param buf pointer to a buffer with the bytes to write
   * @param btr Bytes To Write
   * @param br the number of real written bytes (Bytes Written). NULL if unused.
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_write (lv_fs_file_t * file_p, const void * buf, uint32_t btw, uint32_t * bw);
  
  /**
   * Set the position of the 'cursor' (read write pointer) in a file
   * @param file_p pointer to a lv_fs_file_t variable
   * @param pos the new position expressed in bytes index (0: start of file)
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_seek (lv_fs_file_t * file_p, uint32_t pos);
  
  /**
   * Give the position of the read write pointer
   * @param file_p pointer to a lv_fs_file_t variable
   * @param pos_p pointer to store the position of the read write pointer
   * @return LV_FS_RES_OK or any error from 'fs_res_t'
   */
  lv_fs_res_t lv_fs_tell (lv_fs_file_t * file_p, uint32_t  * pos);
  
  /**
   * Truncate the file size to the current position of the read write pointer
   * @param file_p pointer to an 'ufs_file_t' variable. (opened with lv_fs_open )
   * @return LV_FS_RES_OK: no error, the file is read
   *         any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_trunc (lv_fs_file_t * file_p);
  
  /**
   * Give the size of a file bytes
   * @param file_p pointer to a lv_fs_file_t variable
   * @param size pointer to a variable to store the size
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_size (lv_fs_file_t * file_p, uint32_t * size);
  
  /**
   * Rename a file
   * @param oldname path to the file
   * @param newname path with the new name
   * @return LV_FS_RES_OK or any error from 'fs_res_t'
   */
  lv_fs_res_t lv_fs_rename (const char * oldname, const char * newname);
  
  /**
   * Initialize a 'fs_dir_t' variable for directory reading
   * @param rddir_p pointer to a 'fs_read_dir_t' variable
   * @param path path to a directory
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_dir_open(lv_fs_dir_t * rddir_p, const char * path);
  
  /**
   * Read the next filename form a directory.
   * The name of the directories will begin with '/'
   * @param rddir_p pointer to an initialized 'fs_rdir_t' variable
   * @param fn pointer to a buffer to store the filename
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_dir_read (lv_fs_dir_t * rddir_p, char * fn);
  
  /**
   * Close the directory reading
   * @param rddir_p pointer to an initialized 'fs_dir_t' variable
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_dir_close (lv_fs_dir_t * rddir_p);
  
  /**
   * Get the free and total size of a driver in kB
   * @param letter the driver letter
   * @param total_p pointer to store the total size [kB]
   * @param free_p pointer to store the free size [kB]
   * @return LV_FS_RES_OK or any error from lv_fs_res_t enum
   */
  lv_fs_res_t lv_fs_free (char letter, uint32_t * total_p, uint32_t * free_p);
  
  /**
   * Fill a buffer with the letters of existing drivers
   * @param buf buffer to store the letters ('\0' added after the last letter)
   * @return the buffer
   */
  char *  lv_fs_get_letters(char * buf);
  
  /**
   * Return with the extension of the filename
   * @param fn string with a filename
   * @return pointer to the beginning extension or empty string if no extension
   */
  const char * lv_fs_get_ext(const char * fn);
  
  /**
   * Step up one level
   * @param path pointer to a file name
   * @return the truncated file name
   */
  char * lv_fs_up(char * path);
  
  /**
   * Get the last element of a path (e.g. U:/folder/file -> file)
   * @param buf buffer to store the letters ('\0' added after the last letter)
   * @return pointer to the beginning of the last element in the path
   */
  const char * lv_fs_get_last(const char * path);
  
  /**********************
   *      MACROS
   **********************/
  
  #endif /*USE_LV_FILESYSTEM*/
  
  #ifdef __cplusplus
  } /* extern "C" */
  #endif
  
  #endif /*LV_FS_H*/
  