FIL

The FIL structure (file object) holds the state of an open file. It is created by f_open function and discarded by f_close function. Application program must not modify any member in this structure except for cltbl, or the FAT volume will be collapsed. Note that a sector buffer is defined in this structure at non-tiny configuration (FF_FS_TINY == 0), so that the FIL structures at that configuration should not be defined as auto variable.

typedef struct {
    FFOBJID obj;          /* Object identifier */
    BYTE    flag;         /* File status flags */
    BYTE    err;          /* Abort flag (error code) */
    FSIZE_t fptr;         /* File read/write pointer (byte offset origin from top of the file; 0 on open) */
    DWORD   clust;        /* Current cluster of fptr (one cluster behind if fptr is on the cluster boundary; invalid if fptr == 0) */
    LBA_t   sect;         /* Current data sector (can be invalid if fptr is on the cluster boundary)*/
#if !FF_FS_READONLY
    LBA_t   dir_sect;     /* Sector number containing the directory entry */
    BYTE*   dir_ptr;      /* Pointer to the directory entry in the window */
#endif
#if FF_USE_FASTSEEK
    DWORD*  cltbl;        /* Pointer to the cluster link map table (nulled on file open; set by application) */
#endif
#if !FF_FS_TINY
    BYTE    buf[FF_MAX_SS]; /* File private data transfer buffer (Always valid if fptr is not on the sector boundary but can be invalid if fptr is on the sector boundary.) */
#endif
} FIL;