}

	/* The logical drive has not been mounted, following code attempts to mount the logical drive */

	memset(fs, 0, sizeof(FATFS));		/* Clean-up the file system object */
	stat = disk_initialize(0);			/* Initialize low level disk I/O layer */
	if (stat & STA_NOINIT)				/* Check if the drive is ready */
		return FR_NOT_READY;
#if !_FS_READONLY
	if (chk_wp && (stat & STA_PROTECT))	/* Check write protection if needed */
		return FR_WRITE_PROTECTED;
#endif

	/* Search FAT partition on the drive */
	fmt = check_fs(bootsect = 0);		/* Check sector 0 as an SFD format */
	if (fmt == 1) {						/* Not a FAT boot record, it may be patitioned */
		/* Check a partition listed in top of the partition table */
		if (fs->win[MBR_Table+4]) {					/* Is the 1st partition existing? */
			bootsect = LD_DWORD(&fs->win[MBR_Table+8]);	/* Partition offset in LBA */
			fmt = check_fs(bootsect);				/* Check the partition */
		}
	}
	if (fmt || LD_WORD(&fs->win[BPB_BytsPerSec]) != 512)	/* No valid FAT patition is found */
		return FR_NO_FILESYSTEM;

	/* Initialize the file system object */
	fatsize = LD_WORD(&fs->win[BPB_FATSz16]);			/* Number of sectors per FAT */
	if (!fatsize) fatsize = LD_DWORD(&fs->win[BPB_FATSz32]);
	fs->sects_fat = (CLUST)fatsize;
	fs->n_fats = fs->win[BPB_NumFATs];					/* Number of FAT copies */
	fatsize *= fs->n_fats;								/* (Number of sectors in FAT area) */
	fs->fatbase = bootsect + LD_WORD(&fs->win[BPB_RsvdSecCnt]);	/* FAT start sector (lba) */
	fs->sects_clust = fs->win[BPB_SecPerClus];			/* Number of sectors per cluster */
	fs->n_rootdir = LD_WORD(&fs->win[BPB_RootEntCnt]);	/* Nmuber of root directory entries */
	totalsect = LD_WORD(&fs->win[BPB_TotSec16]);		/* Number of sectors on the file system */
	if (!totalsect) totalsect = LD_DWORD(&fs->win[BPB_TotSec32]);
	fs->max_clust = maxclust = (totalsect				/* Last cluster# + 1 */
		- LD_WORD(&fs->win[BPB_RsvdSecCnt]) - fatsize - fs->n_rootdir / 16
		) / fs->sects_clust + 2;

	fmt = FS_FAT12;										/* Determine the FAT sub type */
	if (maxclust > 0xFF7) fmt = FS_FAT16;
	if (maxclust > 0xFFF7)
#if !_FAT32
		return FR_NO_FILESYSTEM;
#else
		fmt = FS_FAT32;
	if (fmt == FS_FAT32)
		fs->dirbase = LD_DWORD(&fs->win[BPB_RootClus]);	/* Root directory start cluster */
	else
#endif
		fs->dirbase = fs->fatbase + fatsize;			/* Root directory start sector (lba) */
	fs->database = fs->fatbase + fatsize + fs->n_rootdir / 16;	/* Data start sector (lba) */
	fs->fs_type = fmt;									/* FAT sub-type */

#if !_FS_READONLY
	fs->free_clust = (CLUST)0xFFFFFFFF;
#if _USE_FSINFO
	/* Load fsinfo sector if needed */
	if (fmt == FS_FAT32) {
		fs->fsi_sector = bootsect + LD_WORD(&fs->win[BPB_FSInfo]);
		if (disk_read(0, fs->win, fs->fsi_sector, 1) == RES_OK &&
			LD_WORD(&fs->win[BS_55AA]) == 0xAA55 &&
			LD_DWORD(&fs->win[FSI_LeadSig]) == 0x41615252 &&
			LD_DWORD(&fs->win[FSI_StrucSig]) == 0x61417272) {
			fs->last_clust = LD_DWORD(&fs->win[FSI_Nxt_Free]);
			fs->free_clust = LD_DWORD(&fs->win[FSI_Free_Count]);
		}
	}
#endif
#endif
	fs->id = ++fsid;									/* File system mount ID */
	return FR_OK;
}




/*-----------------------------------------------------------------------*/
/* Check if the file/dir object is valid or not                          */
/*-----------------------------------------------------------------------*/

static
FRESULT validate (		/* FR_OK(0): The id is valid, !=0: Not valid */
	const FATFS *fs,	/* Pointer to the file system object */
	WORD id				/* id member of the target object to be checked */
)
{
	if (!fs || fs->id != id)
		return FR_INVALID_OBJECT;
	if (disk_status(0) & STA_NOINIT)
		return FR_NOT_READY;

	return FR_OK;
}




/*--------------------------------------------------------------------------

   Public Functions

--------------------------------------------------------------------------*/


/*-----------------------------------------------------------------------*/
/* Mount/Unmount a Locical Drive                                         */
/*-----------------------------------------------------------------------*/

FRESULT f_mount (
  BYTE drv,		/* Logical drive number to be mounted/unmounted */
  FATFS *fs		/* Pointer to new file system object (NULL for unmount)*/)
{
	FATFS *fsobj;
	if (drv) return FR_INVALID_DRIVE;
	fsobj = FatFs;
	FatFs = fs;
	if(fsobj)  memset(fsobj, 0, sizeof(FATFS));
	if(fs)     memset(fs   , 0, sizeof(FATFS));

	return FR_OK;
}

/*-----------------------------------------------------------------------*/
/* Open or Create a File                                                 */
/*-----------------------------------------------------------------------*/

FRESULT f_open (
	FIL *fp,			    /* Pointer to the blank file object */
	const char *path,	/* Pointer to the file name */
	BYTE mode			    /* Access mode and file open mode flags */)
{
	FRESULT res;
	BYTE *dir;
	DIR dirobj;
	char fn[8+3+1];
	FATFS *fs = FatFs;


	fp->fs = NULL;
#if !_FS_READONLY
	mode &= (FA_READ|FA_WRITE|FA_CREATE_ALWAYS|FA_OPEN_ALWAYS|FA_CREATE_NEW);
	res = auto_mount(&path, (BYTE)(mode & (FA_WRITE|FA_CREATE_ALWAYS|FA_OPEN_ALWAYS|FA_CREATE_NEW)));
#else
	mode &= FA_READ;
	res = auto_mount(&path, 0);
#endif
	if (res != FR_OK) return res;

	/* Trace the file path */
	res = trace_path(&dirobj, fn, path, &dir);	/* Trace the file path */

#if !_FS_READONLY
	/* Create or Open a File */
	if (mode & (FA_CREATE_ALWAYS|FA_OPEN_ALWAYS|FA_CREATE_NEW)) {
		CLUST rs;
		DWORD dw;
		if (res != FR_OK) {		/* No file, create new */
			if (res != FR_NO_FILE) return res;
			res = reserve_direntry(&dirobj, &dir);
			if (res != FR_OK) return res;
			memset(dir, 0, 32);		/* Initialize the new entry */
			memcpy(&dir[DIR_Name], fn, 8+3);
			dir[DIR_NTres] = fn[11];
			mode |= FA_CREATE_ALWAYS;
		} else {				/* Any object is already existing */
			if (mode & FA_CREATE_NEW)			/* Cannot create new */
				return FR_EXIST;
			if (dir == NULL || (dir[DIR_Attr] & (AM_RDO|AM_DIR)))	/* Cannot overwrite (R/O or DIR) */
				return FR_DENIED;
			if (mode & FA_CREATE_ALWAYS) {		/* Resize it to zero */
#if _FAT32
				rs = ((DWORD)LD_WORD(&dir[DIR_FstClusHI]) << 16) | LD_WORD(&dir[DIR_FstClusLO]);
				ST_WORD(&dir[DIR_FstClusHI], 0);
#else
				rs = LD_WORD(&dir[DIR_FstClusLO]);
#endif
				ST_WORD(&dir[DIR_FstClusLO], 0);	/* cluster = 0 */
				ST_DWORD(&dir[DIR_FileSize], 0);	/* size = 0 */
				fs->winflag = 1;
				dw = fs->winsect;				/* Remove the cluster chain */
				if (!remove_chain(rs) || !move_window(dw))
					return FR_RW_ERROR;
				fs->last_clust = rs - 1;		/* Reuse the cluster hole */
			}
		}
		if (mode & FA_CREATE_ALWAYS) {
			dir[DIR_Attr] = AM_ARC;		/* New attribute */
			dw = get_fattime();
			ST_DWORD(&dir[DIR_WrtTime], dw);	/* Updated time */
			ST_DWORD(&dir[DIR_CrtTime], dw);	/* Created time */
			fs->winflag = 1;
		}
	}
	/* Open a File */
	else {
#endif /* !_FS_READONLY */
		if (res != FR_OK) return res;		/* Trace failed */
		if (dir == NULL || (dir[DIR_Attr] & AM_DIR))	/* It is a directory */
			return FR_NO_FILE;
#if !_FS_READONLY
		if ((mode & FA_WRITE) && (dir[DIR_Attr] & AM_RDO)) /* R/O violation */
			return FR_DENIED;
	}

	fp->dir_sect = fs->winsect;			/* Pointer to the directory entry */
	fp->dir_ptr = dir;
#endif
	fp->flag = mode;							/* File access mode */
	fp->org_clust =								/* File start cluster */
#if _FAT32
		((DWORD)LD_WORD(&dir[DIR_FstClusHI]) << 16) |
#endif
		LD_WORD(&dir[DIR_FstClusLO]);
	fp->fsize = LD_DWORD(&dir[DIR_FileSize]);	/* File size */
	fp->fptr = 0;								/* File ptr */
	fp->sect_clust = 1;							/* Sector counter */
	fp->fs = fs; fp->id = fs->id;				/* Owner file system object of the file */

	return FR_OK;
}




/*-----------------------------------------------------------------------*/
/* Read File                                                             */
/*-----------------------------------------------------------------------*/

FRESULT f_read (
	FIL *fp, 		/* Pointer to the file object */
	void *buff,		/* Pointer to data buffer */
	UINT btr,		/* Number of bytes to read */
	UINT *br		/* Pointer to number of bytes read */
)
{
	DWORD sect, remain;
	UINT rcnt, cc;
	CLUST clust;
	BYTE *rbuff = buff;
	FRESULT res;
	FATFS *fs = fp->fs;


	*br = 0;
	res = validate(fs, fp->id);						/* Check validity of the object */
	if (res != FR_OK) return res;
	if (fp->flag & FA__ERROR) return FR_RW_ERROR;	/* Check error flag */
	if (!(fp->flag & FA_READ)) return FR_DENIED;	/* Check access mode */
	remain = fp->fsize - fp->fptr;
	if (btr > remain) btr = (WORD)remain;			/* Truncate read count by number of bytes left */

	for ( ;  btr;									/* Repeat until all data transferred */
		rbuff += rcnt, fp->fptr += rcnt, *br += rcnt, btr -= rcnt) {
		if ((fp->fptr % 512) == 0) {				/* On the sector boundary */
			if (--fp->sect_clust) {					/* Decrement left sector counter */
				sect = fp->curr_sect + 1;			/* Get current sector */
			} else {								/* On the cluster boundary, get next cluster */
				clust = (fp->fptr == 0) ?
					fp->org_clust : get_cluster(fp->curr_clust);
				if (clust < 2 || clust >= fs->max_clust)
					goto fr_error;
				fp->curr_clust = clust;				/* Current cluster */
				sect = clust2sect(clust);			/* Get current sector */
				fp->sect_clust = fs->sects_clust;	/* Re-initialize the left sector counter */
			}
			fp->curr_sect = sect;					/* Update current sector */
			cc = btr / 512;							/* When left bytes >= 512, */
			if (cc) {								/* Read maximum contiguous sectors directly */
				if (cc > fp->sect_clust) cc = fp->sect_clust;
				if (disk_read(0, rbuff, sect, (BYTE)cc) != RES_OK)
					goto fr_error;
				fp->sect_clust -= (BYTE)(cc - 1);
				fp->curr_sect += cc - 1;
				rcnt = cc * 512;
				continue;
			}
		}
		if (!move_window(fp->curr_sect)) goto fr_error;	/* Move sector window */
		rcnt = 512 - (WORD)(fp->fptr % 512);			/* Copy fractional bytes from sector window */
		if (rcnt > btr) rcnt = btr;
		memcpy(rbuff, &fs->win[(WORD)fp->fptr % 512], rcnt);
	}

	return FR_OK;

fr_error:	/* Abort this function due to an unrecoverable error */
	fp->flag |= FA__ERROR;
	return FR_RW_ERROR;
}




#if !_FS_READONLY
/*-----------------------------------------------------------------------*/
/* Write File                                                            */
/*-----------------------------------------------------------------------*/

FRESULT f_write (
	FIL *fp,			/* Pointer to the file object */
	const void *buff,	/* Pointer to the data to be written */
	UINT btw,			/* Number of bytes to write */
	UINT *bw			/* Pointer to number of bytes written */
)
{
	DWORD sect;
	UINT wcnt, cc;
	CLUST clust;
	FRESULT res;
//	const BYTE *wbuff = buff;
	BYTE *wbuff = buff;
	FATFS *fs = fp->fs;


	*bw = 0;
	res = validate(fs, fp->id);						/* Check validity of the object */
	if (res != FR_OK) return res;
	if (fp->flag & FA__ERROR) return FR_RW_ERROR;	/* Check error flag */
	if (!(fp->flag & FA_WRITE)) return FR_DENIED;	/* Check access mode */
	if (fp->fsize + btw < fp->fsize) return FR_OK;	/* File size cannot reach 4GB */

	for ( ;  btw;									/* Repeat until all data transferred */
		wbuff += wcnt, fp->fptr += wcnt, *bw += wcnt, btw -= wcnt) {
		if ((fp->fptr % 512) == 0) {				/* On the sector boundary */
			if (--(fp->sect_clust)) {				/* Decrement left sector counter */
				sect = fp->curr_sect + 1;			/* Get current sector */
			} else {								/* On the cluster boundary, get next cluster */
				if (fp->fptr == 0) {				/* Is top of the file */
					clust = fp->org_clust;
					if (clust == 0)					/* No cluster is created yet */
						fp->org_clust = clust = create_chain(0);	/* Create a new cluster chain */
				} else {							/* Middle or end of file */
					clust = create_chain(fp->curr_clust);			/* Trace or streach cluster chain */
				}
				if (clust == 0) break;				/* Disk full */
				if (clust == 1 || clust >= fs->max_clust) goto fw_error;
				fp->curr_clust = clust;				/* Current cluster */
				sect = clust2sect(clust);			/* Get current sector */
				fp->sect_clust = fs->sects_clust;	/* Re-initialize the left sector counter */
			}
			fp->curr_sect = sect;					/* Update current sector */
			cc = btw / 512;							/* When left bytes >= 512, */
			if (cc) {								/* Write maximum contiguous sectors directly */
				if (cc > fp->sect_clust) cc = fp->sect_clust;
				if (disk_write(0, wbuff, sect, (BYTE)cc) != RES_OK)
					goto fw_error;
				fp->sect_clust -= (BYTE)(cc - 1);
				fp->curr_sect += cc - 1;
				wcnt = cc * 512;
				continue;
			}
			if (fp->fptr >= fp->fsize) {			/* Flush R/W window if needed */
				if (!move_window(0)) goto fw_error;
				fs->winsect = fp->curr_sect;
			}
		}
		if (!move_window(fp->curr_sect))			/* Move sector window */
			goto fw_error;
		wcnt = 512 - (WORD)(fp->fptr % 512);		/* Copy fractional bytes bytes to sector window */
		if (wcnt > btw) wcnt = btw;
		memcpy(&fs->win[(WORD)fp->fptr % 512], wbuff, wcnt);
		fs->winflag = 1;
	}

	if (fp->fptr > fp->fsize) fp->fsize = fp->fptr;	/* Update file size if needed */
	fp->flag |= FA__WRITTEN;						/* Set file changed flag */
	return FR_OK;

fw_error:	/* Abort this function due to an unrecoverable error */
	fp->flag |= FA__ERROR;
	return FR_RW_ERROR;
}




/*-----------------------------------------------------------------------*/
/* Synchronize the file object                                           */
/*-----------------------------------------------------------------------*/

FRESULT f_sync (
	FIL *fp		/* Pointer to the file object */
)
{
	DWORD tim;
	BYTE *dir;
	FRESULT res;
	FATFS *fs = fp->fs;


	res = validate(fs, fp->id);				/* Check validity of the object */
	if (res == FR_OK) {
		if (fp->flag & FA__WRITTEN) {		/* Has the file been written? */
			/* Update the directory entry */
			if (!move_window(fp->dir_sect))
				return FR_RW_ERROR;
			dir = fp->dir_ptr;
			dir[DIR_Attr] |= AM_ARC;						/* Set archive bit */
			ST_DWORD(&dir[DIR_FileSize], fp->fsize);		/* Update file size */
			ST_WORD(&dir[DIR_FstClusLO], fp->org_clust);	/* Update start cluster */
#if _FAT32
			ST_WORD(&dir[DIR_FstClusHI], fp->org_clust >> 16);
#endif
			tim = get_fattime();					/* Updated time */
			ST_DWORD(&dir[DIR_WrtTime], tim);
			fp->flag &= ~FA__WRITTEN;
			res = sync();
		}
	}
	return res;
}

#endif /* !_FS_READONLY */