fatfs f_readdir 在使用长文件名时的问题

fatfs f_readdir 在使用长文件名时的问题

结论先行

FRESULT f_readdir (DIR* dp, FILINFO* fno)

在使用了长文件名后，在操作f_readdir前，需要初始化fno.lfsize

	
	FILINFO info;
	TCHAR name[64];
	int res;
	DIR file_dir;
	
	info.lfname = name;
	info.lfsize = 64;  //init lfsize

	f_opendir(&file_dir, PICTURE_FILE_DIR);
	f_readdir(&file_dir, &info);

分析过程

在使能了长文件名后，通过f_readdir遍历目录下的文件，发现获取到的lfname为空，代码如下

++log++

[DBG]-[NORMAL]\USER\main.c\list_for_each_pic\read dir, res=0, fname=PIC201~1.BMP, lfname=
[DBG]-[NORMAL]\USER\main.c\list_for_each_pic\read dir, res=0, fname=PIC201~2.BMP, lfname=
[DBG]-[NORMAL]\USER\main.c\list_for_each_pic\read dir, res=0, fname=PIC201~3.BMP, lfname=

++code++

static void list_for_each_pic(char *debug)
{
	FILINFO info;
	TCHAR name[64];
	int res;
	DIR file_dir;
	
	info.lfname = name;

	DBG_TO_SERIAL(DBG_NORMAL, "%s", debug);

	res = f_opendir(&file_dir, PICTURE_FILE_DIR);
	if (res) {
		DBG_TO_SERIAL(DBG_NORMAL, "can not open dir:%s, res=%d", PICTURE_FILE_DIR, res);
		my_msg.sf_lock = 0;
		return;
	}

	/* read picture file */
	while (1) {
		res = f_readdir(&file_dir, &info);
		DBG_TO_SERIAL(DBG_NORMAL, "read dir, res=%d, fname=%s, lfname=%s", res, info.fname, info.lfname);
		if (res || info.fname[0] == 0)
			break;
		if (info.fname[0] == '.')
			continue;		
	}
	f_closedir(&file_dir);
}

追踪fatfs代码，发现有如下机制

if (dp->sect && fno->lfsize && dp->lfn_idx != 0xFFFF) { /* Get LFN if available */

通过添加打印，发现出现获取不到lfname时的lfzise为0

/*-----------------------------------------------------------------------*/
/* Get file information from directory entry                             */
/*-----------------------------------------------------------------------*/
#if _FS_MINIMIZE <= 1 || _FS_RPATH >= 2
static
void get_fileinfo (		/* No return code */
	DIR* dp,			/* Pointer to the directory object */
	FILINFO* fno	 	/* Pointer to the file information to be filled */
)
{
	UINT i;
	TCHAR *p, c;
	BYTE *dir;
#if _USE_LFN
	WCHAR w, *lfn;
#endif

	p = fno->fname;
	if (dp->sect) {		/* Get SFN */
		dir = dp->dir;
		i = 0;
		while (i < 11) {		/* Copy name body and extension */
			c = (TCHAR)dir[i++];
			if (c == ' ') continue;				/* Skip padding spaces */
			if (c == RDDEM) c = (TCHAR)DDEM;	/* Restore replaced DDEM character */
			if (i == 9) *p++ = '.';				/* Insert a . if extension is exist */
#if _USE_LFN
			if (IsUpper(c) && (dir[DIR_NTres] & (i >= 9 ? NS_EXT : NS_BODY)))
				c += 0x20;			/* To lower */
#if _LFN_UNICODE
			if (IsDBCS1(c) && i != 8 && i != 11 && IsDBCS2(dir[i]))
				c = c << 8 | dir[i++];
			c = ff_convert(c, 1);	/* OEM -> Unicode */
			if (!c) c = '?';
#endif
#endif
			*p++ = c;
		}
		fno->fattrib = dir[DIR_Attr];				/* Attribute */
		fno->fsize = LD_DWORD(dir + DIR_FileSize);	/* Size */
		fno->fdate = LD_WORD(dir + DIR_WrtDate);	/* Date */
		fno->ftime = LD_WORD(dir + DIR_WrtTime);	/* Time */
	}
	*p = 0;		/* Terminate SFN string by a \0 */

#if _USE_LFN
	if (fno->lfname) {
		i = 0; p = fno->lfname;
		if (dp->sect && fno->lfsize && dp->lfn_idx != 0xFFFF) {	/* Get LFN if available */
			lfn = dp->lfn;
			while ((w = *lfn++) != 0) {		/* Get an LFN character */
#if !_LFN_UNICODE
				w = ff_convert(w, 0);		/* Unicode -> OEM */
				if (!w) { i = 0; break; }	/* No LFN if it could not be converted */
				if (_DF1S && w >= 0x100)	/* Put 1st byte if it is a DBC (always false on SBCS cfg) */
					p[i++] = (TCHAR)(w >> 8);
#endif
				if (i >= fno->lfsize - 1) { i = 0; break; }	/* No LFN if buffer overflow */
				p[i++] = (TCHAR)w;
			}
		}
		p[i] = 0;	/* Terminate LFN string by a \0 */
	}
#endif
}
#endif /* _FS_MINIMIZE <= 1 || _FS_RPATH >= 2 */



/*-----------------------------------------------------------------------*/
/* Read Directory Entries in Sequence                                    */
/*-----------------------------------------------------------------------*/

FRESULT f_readdir (
	DIR* dp,			/* Pointer to the open directory object */
	FILINFO* fno		/* Pointer to file information to return */
)
{
	FRESULT res;
	DEFINE_NAMEBUF;


	res = validate(dp);						/* Check validity of the object */
	if (res == FR_OK) {
		if (!fno) {
			res = dir_sdi(dp, 0);			/* Rewind the directory object */
		} else {
			INIT_BUF(*dp);
			res = dir_read(dp, 0);			/* Read an item */
			if (res == FR_NO_FILE) {		/* Reached end of directory */
				dp->sect = 0;
				res = FR_OK;
			}
			if (res == FR_OK) {				/* A valid entry is found */
				get_fileinfo(dp, fno);		/* Get the object information */
				res = dir_next(dp, 0);		/* Increment index for next */
				if (res == FR_NO_FILE) {
					dp->sect = 0;
					res = FR_OK;
				}
			}
			FREE_BUF();
		}
	}

	LEAVE_FF(dp->fs, res);
}

对lfsize进行搜索，看在什么位置进行的赋值

Ff.c (\fat_fs\src):	if (fno->lfname && fno->lfsize) {
Ff.c (\fat_fs\src):				if (i >= fno->lfsize - 1) { i = 0; break; }	/* Buffer overflow, no LFN */
Ff.c (\fat_fs\src):			fno.lfsize = i;
Ff.h (\fat_fs\inc):	UINT 	lfsize;			/* Size of LFN buffer in TCHAR */

发现其实没有任何位置对此变量进行赋值

#if _FS_RPATH >= 2
FRESULT f_getcwd (
	TCHAR *path,	/* Pointer to the directory path */
	UINT sz_path	/* Size of path */
)
{
	FRESULT res;
	DIR dj;
	UINT i, n;
	DWORD ccl;
	TCHAR *tp;
	FILINFO fno;
	DEF_NAMEBUF;


	*path = 0;
	res = chk_mounted((const TCHAR**)&path, &dj.fs, 0);	/* Get current volume */
	if (res == FR_OK) {
		INIT_BUF(dj);
		i = sz_path;		/* Bottom of buffer (dir stack base) */
		dj.sclust = dj.fs->cdir;			/* Start to follow upper dir from current dir */
		while ((ccl = dj.sclust) != 0) {	/* Repeat while current dir is a sub-dir */
			res = dir_sdi(&dj, 1);			/* Get parent dir */
			if (res != FR_OK) break;
			res = dir_read(&dj);
			if (res != FR_OK) break;
			dj.sclust = LD_CLUST(dj.dir);	/* Goto parent dir */
			res = dir_sdi(&dj, 0);
			if (res != FR_OK) break;
			do {							/* Find the entry links to the child dir */
				res = dir_read(&dj);
				if (res != FR_OK) break;
				if (ccl == LD_CLUST(dj.dir)) break;	/* Found the entry */
				res = dir_next(&dj, 0);	
			} while (res == FR_OK);
			if (res == FR_NO_FILE) res = FR_INT_ERR;/* It cannot be 'not found'. */
			if (res != FR_OK) break;
#if _USE_LFN
			fno.lfname = path;
			fno.lfsize = i;
#endif
			get_fileinfo(&dj, &fno);		/* Get the dir name and push it to the buffer */
			tp = fno.fname;
			if (_USE_LFN && *path) tp = path;
			for (n = 0; tp[n]; n++) ;
			if (i < n + 3) {
				res = FR_NOT_ENOUGH_CORE; break;
			}
			while (n) path[--i] = tp[--n];
			path[--i] = '/';
		}
		tp = path;
		if (res == FR_OK) {
			*tp++ = '0' + CurrVol;			/* Put drive number */
			*tp++ = ':';
			if (i == sz_path) {				/* Root-dir */
				*tp++ = '/';
			} else {						/* Sub-dir */
				do		/* Add stacked path str */
					*tp++ = path[i++];
				while (i < sz_path);
			}
		}
		*tp = 0;
		FREE_BUF();
	}

	LEAVE_FF(dj.fs, res);
}
#endif /* _FS_RPATH >= 2 */
#endif /* _FS_RPATH >= 1 */

结论

// lfsize仅有一个作用，就是用来限制i，防止内存越界，lfsize需要在使用f_readdir之前自己手动赋值

#if _USE_LFN
	if (fno->lfname) {
		i = 0; p = fno->lfname;
		if (dp->sect && fno->lfsize && dp->lfn_idx != 0xFFFF) {	/* Get LFN if available */
			lfn = dp->lfn;
			while ((w = *lfn++) != 0) {		/* Get an LFN character */
#if !_LFN_UNICODE
				w = ff_convert(w, 0);		/* Unicode -> OEM */
				if (!w) { i = 0; break; }	/* No LFN if it could not be converted */
				if (_DF1S && w >= 0x100)	/* Put 1st byte if it is a DBC (always false on SBCS cfg) */
					p[i++] = (TCHAR)(w >> 8);
#endif
				if (i >= fno->lfsize - 1) { i = 0; break; }	/* No LFN if buffer overflow */
				p[i++] = (TCHAR)w;
			}
		}
		p[i] = 0;	/* Terminate LFN string by a \0 */
	}
#endif