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  15 <h2>FATFS</h2>
  16 <p>The <tt>FATFS</tt> structure (file system object) holds dynamic work area of individual logical drives. It is given by application program and registerd/unregisterd to the FatFs module with <tt>f_mount</tt> function. Initialization is done on first API call after <tt>f_mount</tt> function or media change. Application program must not modify any member in this structure, or any data on the FAT volume can be collapsed.</p>
  17 <pre>
  18 <span class="k">typedef</span> <span class="k">struct</span> {
  19     BYTE    fs_type;      <span class="c">/* File system type (0, FS_FAT12, FS_FAT16, FS_FAT32 or FS_EXFAT) */</span>
  20     BYTE    drv;          <span class="c">/* Physical drive number */</span>
  21     BYTE    n_fats;       <span class="c">/* Number of FAT copies (1,2) */</span>
  22     BYTE    wflag;        <span class="c">/* win[] flag (b0:win[] is dirty) */</span>
  23     BYTE    fsi_flag;     <span class="c">/* FSINFO flags (b7:Disabled, b0:Dirty) */</span>
  24     WORD    id;           <span class="c">/* File system mount ID */</span>
  25     WORD    n_rootdir;    <span class="c">/* Number of root directory entries (FAT12/16) */</span>
  26     WORD    csize;        <span class="c">/* Sectors per cluster */</span>
  27 <span class="k">#if</span> _MAX_SS != _MIN_SS
  28     WORD    ssize;        <span class="c">/* Sector size (512,1024,2048 or 4096) */</span>
  29 <span class="k">#endif</span>
  30 <span class="k">#if _FS_EXFAT</span>
  31     BYTE*   dirbuf;       <span class="c">/* Directory entry block scratchpad buffer */</span>
  32 <span class="k">#endif</span>
  33 <span class="k">#if</span> _FS_REENTRANT
  34     _SYNC_t sobj;         <span class="c">/* Identifier of sync object */</span>
  35 <span class="k">#endif</span>
  36 <span class="k">#if</span> !_FS_READONLY
  37     DWORD   last_clust;   <span class="c">/* FSINFO: Last allocated cluster (0xFFFFFFFF if invalid) */</span>
  38     DWORD   free_clust;   <span class="c">/* FSINFO: Number of free clusters (0xFFFFFFFF if invalid) */</span>
  39 <span class="k">#endif</span>
  40 <span class="k">#if</span> _FS_RPATH
  41     DWORD   cdir;         <span class="c">/* Cluster number of current directory (0:root) */</span>
  42 <span class="k">#if _FS_EXFAT</span>
  43     DWORD   cdc_scl;      <span class="c">/* Containing directory start cluster (invalid when cdir is 0) */</span>
  44     DWORD   cdc_size;     <span class="c">/* b31-b8:Size of containing directory, b7-b0: Chain status */</span>
  45     DWORD   cdc_ofs;      <span class="c">/* Offset in the containing directory (invalid when cdir is 0) */</span>
  46 <span class="k">#endif</span>
  47 <span class="k">#endif</span>
  48     DWORD   n_fatent;     <span class="c">/* Number of FAT entries (Number of clusters + 2) */</span>
  49     DWORD   fsize;        <span class="c">/* Sectors per FAT */</span>
  50     DWORD   volbase;      <span class="c">/* Volume base LBA */</span>
  51     DWORD   fatbase;      <span class="c">/* FAT base LBA */</span>
  52     DWORD   dirbase;      <span class="c">/* Root directory base (LBA|Cluster) */</span>
  53     DWORD   database;     <span class="c">/* Data base LBA */</span>
  54     DWORD   winsect;      <span class="c">/* Sector LBA appearing in the win[] */</span>
  55     BYTE    win[_MAX_SS]; <span class="c">/* Disk access window for directory, FAT (and file data at tiny cfg) */</span>
  56 } FATFS;
  57 </pre>
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