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
[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=
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