if (clust < 2 || clust >= fp->fs->max_clust) goto fr_error;
				fp->curr_clust = clust;				/* Update current cluster */
				fp->csect = 0;						/* Reset sector address in the cluster */
			}
			sect = clust2sect(fp->curr_clust) + fp->csect;	/* Get current sector */
			cc = btr / 512U;						/* When remaining bytes >= sector size, */
			if (cc) {								/* Read maximum contiguous sectors directly */
				if (fp->csect + cc > fp->fs->csize)	/* Clip at cluster boundary */
					cc = fp->fs->csize - fp->csect;
				if (disk_read(0, rbuff, sect, (BYTE)cc) != RES_OK)
					goto fr_error;
				fp->csect += (BYTE)cc;				/* Next sector address in the cluster */
				rcnt = 512U * cc;					/* Number of bytes transferred */
				continue;
			}
			fp->csect++;							/* Next sector address in the cluster */
		}
		sect = clust2sect(fp->curr_clust) + fp->csect - 1;	/* Get current sector */
		if (!move_window(sect)) goto fr_error;		/* Move sector window */
		rcnt = 512U - (fp->fptr % 512U);			/* Get partial sector from sector window */
		if (rcnt > btr) rcnt = btr;
		memcpy(rbuff, &fp->fs->win[fp->fptr % 512U], rcnt);
	}

	return FR_OK;

fr_error:	/* Abort this file 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 */
)
{
	FRESULT res;
	DWORD sect;
	UINT wcnt, cc;
	CLUST clust;
	const BYTE *wbuff = buff;


	*bw = 0;
	res = validate(fp->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 % 512U) == 0) {				/* On the sector boundary? */
			if (fp->csect >= fp->fs->csize) {		/* On the cluster boundary? */
				if (fp->fptr == 0) {				/* On the top of the file? */
					clust = fp->org_clust;			/* Follow from the origin */
					if (clust == 0)					/* When there is no cluster chain, */
						fp->org_clust = clust = create_chain(0);	/* Create a new cluster chain */
				} else {							/* Middle or end of the file */
					clust = create_chain(fp->curr_clust);			/* Trace or streach cluster chain */
				}
				if (clust == 0) break;				/* Could not allocate a new cluster (disk full) */
				if (clust == 1 || clust >= fp->fs->max_clust) goto fw_error;
				fp->curr_clust = clust;				/* Update current cluster */
				fp->csect = 0;						/* Reset sector address in the cluster */
			}
			sect = clust2sect(fp->curr_clust) + fp->csect;	/* Get current sector */
			cc = btw / 512U;						/* When remaining bytes >= sector size, */
			if (cc) {								/* Write maximum contiguous sectors directly */
				if (fp->csect + cc > fp->fs->csize)	/* Clip at cluster boundary */
					cc = fp->fs->csize - fp->csect;
				if (disk_write(0, wbuff, sect, (BYTE)cc) != RES_OK)
					goto fw_error;
				fp->csect += (BYTE)cc;				/* Next sector address in the cluster */
				wcnt = 512U * cc;					/* Number of bytes transferred */
				continue;
			}
			if (fp->fptr >= fp->fsize) {			/* Flush R/W window without reading if needed */
				if (!move_window(0)) goto fw_error;
				fp->fs->winsect = sect;
			}
			fp->csect++;							/* Next sector address in the cluster */
		}
		sect = clust2sect(fp->curr_clust) + fp->csect - 1;	/* Get current sector */
		if (!move_window(sect)) goto fw_error;		/* Move sector window */
		wcnt = 512U - (fp->fptr % 512U);			/* Put partial sector into sector window */
		if (wcnt > btw) wcnt = btw;
		memcpy(&fp->fs->win[fp->fptr % 512U], wbuff, wcnt);
		fp->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 res;

fw_error:	/* Abort this file 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 */
)
{
	FRESULT res;
	DWORD tim;
	BYTE *dir;


	res = validate(fp->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 &= (BYTE)~FA__WRITTEN;
			res = sync();
		}
	}
	return res;
}

#endif /* !_FS_READONLY */



/*-----------------------------------------------------------------------*/
/* Close File                                                            */
/*-----------------------------------------------------------------------*/

FRESULT f_close (
	FIL *fp		/* Pointer to the file object to be closed */
)
{
	FRESULT res;


#if !_FS_READONLY
	res = f_sync(fp);
#else
	res = validate(fp->fs, fp->id);
#endif
	if (res == FR_OK) fp->fs = NULL;
	return res;
}




#if _FS_MINIMIZE <= 2
/*-----------------------------------------------------------------------*/
/* Seek File R/W Pointer                                                 */
/*-----------------------------------------------------------------------*/

FRESULT f_lseek (
	FIL *fp,		/* Pointer to the file object */
	DWORD ofs		/* File pointer from top of file */
)
{
	FRESULT res;
	CLUST clust;
	DWORD csize, ifptr;


	res = validate(fp->fs, fp->id);			/* Check validity of the object */
	if (res != FR_OK) return res;
	if (fp->flag & FA__ERROR) return FR_RW_ERROR;
	if (ofs > fp->fsize					/* In read-only mode, clip offset with the file size */
#if !_FS_READONLY
		 && !(fp->flag & FA_WRITE)
#endif
		) ofs = fp->fsize;

	ifptr = fp->fptr;
	fp->fptr = 0; fp->csect = 255;
	if (ofs > 0) {
		csize = (DWORD)fp->fs->csize * 512U;		/* Cluster size (byte) */
		if (ifptr > 0 &&
			(ofs - 1) / csize >= (ifptr - 1) / csize) {/* When seek to same or following cluster, */
			fp->fptr = (ifptr - 1) & ~(csize - 1);	/* start from the current cluster */
			ofs -= fp->fptr;
			clust = fp->curr_clust;
		} else {									/* When seek to back cluster, */
			clust = fp->org_clust;					/* start from the first cluster */
#if !_FS_READONLY
			if (clust == 0) {						/* If no cluster chain, create a new chain */
				clust = create_chain(0);
				if (clust == 1) goto fk_error;
				fp->org_clust = clust;
			}
#endif
			fp->curr_clust = clust;
		}
		if (clust != 0) {
			while (ofs > csize) {					/* Cluster following loop */
#if !_FS_READONLY
				if (fp->flag & FA_WRITE) {			/* Check if in write mode or not */
					clust = create_chain(clust);	/* Force streached if in write mode */
					if (clust == 0) {				/* When disk gets full, clip file size */
						ofs = csize; break;
					}
				} else
#endif
					clust = get_cluster(clust);		/* Follow cluster chain if not in write mode */
				if (clust < 2 || clust >= fp->fs->max_clust) goto fk_error;
				fp->curr_clust = clust;
				fp->fptr += csize;
				ofs -= csize;
			}
			fp->fptr += ofs;
			fp->csect = (BYTE)(ofs / 512U);	/* Sector offset in the cluster */
			if (ofs % 512U) fp->csect++;
		}
	}

#if !_FS_READONLY
	if (fp->fptr > fp->fsize) {			/* Set changed flag if the file was extended */
		fp->fsize = fp->fptr;
		fp->flag |= FA__WRITTEN;
	}
#endif

	return FR_OK;

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




#if _FS_MINIMIZE <= 1
/*-----------------------------------------------------------------------*/
/* Create a directroy object                                             */
/*-----------------------------------------------------------------------*/

FRESULT f_opendir (
	DIR *dj,			/* Pointer to directory object to create */
	const char *path	/* Pointer to the directory path */
)
{
	FRESULT res;
	BYTE *dir;
	char fn[8+3+1];


	res = auto_mount(&path, 0);
	if (res == FR_OK) {
		res = trace_path(dj, fn, path, &dir);	/* Trace the directory path */
		if (res == FR_OK) {						/* Trace completed */
			if (dir) {							/* It is not the root dir */
				if (dir[DIR_Attr] & AM_DIR) {	/* The entry is a directory */
	 				dj->clust =
#if _FAT32
						((DWORD)LD_WORD(&dir[DIR_FstClusHI]) << 16) |
#endif
							LD_WORD(&dir[DIR_FstClusLO]);
					dj->sect = clust2sect(dj->clust);
					dj->index = 2;
				} else {						/* The entry is not a directory */
					res = FR_NO_FILE;
				}
			}
			dj->id = dj->fs->id;
		}
	}

	return res;
}




/*-----------------------------------------------------------------------*/
/* Read Directory Entry in Sequense                                      */
/*-----------------------------------------------------------------------*/

FRESULT f_readdir (
	DIR *dj,			/* Pointer to the directory object */
	FILINFO *finfo		/* Pointer to file information to return */
)
{
	FRESULT res;
	BYTE *dir, c;


	res = validate(dj->fs, dj->id);			/* Check validity of the object */
	if (res != FR_OK) return res;

	finfo->fname[0] = 0;
	while (dj->sect) {
		if (!move_window(dj->sect))
			return FR_RW_ERROR;
		dir = &dj->fs->win[(dj->index & 15) * 32];	/* pointer to the directory entry */
		c = dir[DIR_Name];
		if (c == 0) break;							/* Has it reached to end of dir? */
		if (c != 0xE5 && !(dir[DIR_Attr] & AM_VOL))	/* Is it a valid entry? */
			get_fileinfo(finfo, dir);
		if (!next_dir_entry(dj)) dj->sect = 0;		/* Next entry */
		if (finfo->fname[0]) break;					/* Found valid entry */
	}

	return FR_OK;
}




#if _FS_MINIMIZE == 0
/*-----------------------------------------------------------------------*/
/* Get File Status                                                       */
/*-----------------------------------------------------------------------*/

FRESULT f_stat (
	const char *path,	/* Pointer to the file path */
	FILINFO *finfo		/* Pointer to file information to return */
)
{
	FRESULT res;
	DIR dj;
	BYTE *dir;
	char fn[8+3+1];


	res = auto_mount(&path, 0);
	if (res == FR_OK) {
		res = trace_path(&dj, fn, path, &dir);	/* Trace the file path */
		if (res == FR_OK) {						/* Trace completed */
			if (dir)	/* Found an object */
				get_fileinfo(finfo, dir);
			else		/* It is root dir */
				res = FR_INVALID_NAME;
		}
	}

	return res;
}




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

FRESULT f_truncate (
	FIL *fp		/* Pointer to the file object */
)
{
	FRESULT res;
	CLUST ncl;


	res = validate(fp->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 > fp->fptr) {
		fp->fsize = fp->fptr;	/* Set file size to current R/W point */
		fp->flag |= FA__WRITTEN;
		if (fp->fptr == 0) {	/* When set file size to zero, remove entire cluster chain */
			if (!remove_chain(fp->org_clust)) goto ft_error;
			fp->org_clust = 0;
		} else {				/* When truncate a part of the file, remove remaining clusters */
			ncl = get_cluster(fp->curr_clust);
			if (ncl < 2) goto ft_error;
			if (ncl < fp->fs->max_clust) {
				if (!put_cluster(fp->curr_clust, (CLUST)0x0FFFFFFF)) goto ft_error;
				if (!remove_chain(ncl)) goto ft_error;
			}
		}
	}

	return FR_OK;

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




/*-----------------------------------------------------------------------*/
/* Get Number of Free Clusters                                           */
/*-----------------------------------------------------------------------*/

FRESULT f_getfree (
	const char *drv,	/* Pointer to the logical drive number (root dir) */
	DWORD *nclust,		/* Pointer to the variable to return number of free clusters */
	FATFS **fatfs		/* Pointer to pointer to corresponding file system object to return */
)
{
	FRESULT res;
	FATFS *fs;
	DWORD n, sect;
	CLUST clust;
	BYTE fat, f, *p;


	/* Get drive number */
	res = auto_mount(&drv, 0);
	if (res != FR_OK) return res;
	*fatfs = fs = FatFs;

	/* If number of free cluster is valid, return it without cluster scan. */
	if (fs->free_clust <= fs->max_clust - 2) {
		*nclust = fs->free_clust;
		return FR_OK;
	}

	/* Get number of free clusters */
	fat = fs->fs_type;
	n = 0;
	if (fat == FS_FAT12) {
		clust = 2;
		do {
			if ((WORD)get_cluster(clust) == 0) n++;
		} while (++clust < fs->max_clust);
	} else {
		clust = fs->max_clust;
		sect = fs->fatbase;
		f = 0; p = 0;
		do {
			if (!f) {
				if (!move_window(sect++)) return FR_RW_ERROR;
				p = fs->win;
			}
			if (!_FAT32 || fat == FS_FAT16) {
				if (LD_WORD(p) == 0) n++;
				p += 2; f += 1;
			} else {
				if (LD_DWORD(p) == 0) n++;
				p += 4; f += 2;
			}
		} while (--clust);
	}
	fs->free_clust = n;
#if _USE_FSINFO
	if (fat == FS_FAT32) fs->fsi_flag = 1;
#endif