PokittoLib

File content as of revision 2:968589ca3484:

/*----------------------------------------------------------------------------/
/  Petit FatFs - FAT file system module  R0.02                 (C)ChaN, 2009
/-----------------------------------------------------------------------------/
/ Petit FatFs module is an open source software to implement FAT file system to
/ small embedded systems. This is a free software and is opened for education,
/ research and commercial developments under license policy of following trems.
/
/  Copyright (C) 2009, ChaN, all right reserved.
/
/ * The Petit FatFs module is a free software and there is NO WARRANTY.
/ * No restriction on use. You can use, modify and redistribute it for
/   personal, non-profit or commercial use UNDER YOUR RESPONSIBILITY.
/ * Redistributions of source code must retain the above copyright notice.
/
/-----------------------------------------------------------------------------/
/ Jun 15,'09  R0.01a  First release. (Branched from FatFs R0.07b.)
/
/ Dec 14,'09  R0.02   Added multiple code page support.
/                     Added write funciton.
/                     Changed stream read mode interface.
/----------------------------------------------------------------------------*/

#include "pff.h"        /* Petit FatFs configurations and declarations */
#include "diskio.h"        /* Declarations of low level disk I/O functions */


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

   Private Functions

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

static
FATFS *FatFs;    /* Pointer to the file system object (logical drive) */



/*-----------------------------------------------------------------------*/
/* String functions                                                      */
/*-----------------------------------------------------------------------*/

/* Fill memory */
static
void mem_set (void* dst, int val, int cnt) {
    char *d = (char*)dst;
    while (cnt--) *d++ = (char)val;
}

/* Compare memory to memory */
static
int mem_cmp (const void* dst, const void* src, int cnt) {
    const char *d = (const char *)dst, *s = (const char *)src;
    int r = 0;
    while (cnt-- && (r = *d++ - *s++) == 0) ;
    return r;
}



/*-----------------------------------------------------------------------*/
/* FAT access - Read value of a FAT entry                                */
/*-----------------------------------------------------------------------*/

static
CLUST get_fat (    /* 1:IO error, Else:Cluster status */
    CLUST clst    /* Cluster# to get the link information */
) {
    WORD wc, bc, ofs;
    BYTE buf[4];
    FATFS *fs = FatFs;


    if (clst < 2 || clst >= fs->max_clust)    /* Range check */
        return 1;

    switch (fs->fs_type) {
        case FS_FAT12 :
            bc = (WORD)clst;
            bc += bc / 2;
            ofs = bc % 512;
            bc /= 512;
            if (ofs != 511) {
                if (disk_readp(buf, fs->fatbase + bc, ofs, 2)) break;
            } else {
                if (disk_readp(buf, fs->fatbase + bc, 511, 1)) break;
                if (disk_readp(buf+1, fs->fatbase + bc + 1, 0, 1)) break;
            }
            wc = LD_WORD(buf);
            return (clst & 1) ? (wc >> 4) : (wc & 0xFFF);

        case FS_FAT16 :
            if (disk_readp(buf, fs->fatbase + clst / 256, (WORD)(((WORD)clst % 256) * 2), 2)) break;
            return LD_WORD(buf);
#if _FS_FAT32
        case FS_FAT32 :
            if (disk_readp(buf, fs->fatbase + clst / 128, (WORD)(((WORD)clst % 128) * 4), 4)) break;
            return ((WORD)(((WORD)*(BYTE*)((buf)+1)<<8)|(WORD)*(BYTE*)(buf))) & 0x0FFFFFFF; //return LD_DWORD(buf) & 0x0FFFFFFF; //get rid of out of bounds warning in online IDE
#endif
    }

    return 1;    /* An error occured at the disk I/O layer */
}




/*-----------------------------------------------------------------------*/
/* Get sector# from cluster#                                             */
/*-----------------------------------------------------------------------*/

static
DWORD clust2sect (    /* !=0: Sector number, 0: Failed - invalid cluster# */
    CLUST clst        /* Cluster# to be converted */
) {
    FATFS *fs = FatFs;


    clst -= 2;
    if (clst >= (fs->max_clust - 2)) return 0;        /* Invalid cluster# */
    return (DWORD)clst * fs->csize + fs->database;
}




/*-----------------------------------------------------------------------*/
/* Directory handling - Rewind directory index                           */
/*-----------------------------------------------------------------------*/

static
FRESULT dir_rewind (
    FATDIR *dj            /* Pointer to directory object */
) {
    CLUST clst;
    FATFS *fs = FatFs;


    dj->index = 0;
    clst = dj->sclust;
    if (clst == 1 || clst >= fs->max_clust)    /* Check start cluster range */
        return FR_DISK_ERR;
#if _FS_FAT32
    if (!clst && fs->fs_type == FS_FAT32)    /* Replace cluster# 0 with root cluster# if in FAT32 */
        clst = fs->dirbase;
#endif
    dj->clust = clst;                        /* Current cluster */
    dj->sect = clst ? clust2sect(clst) : fs->dirbase;    /* Current sector */

    return FR_OK;    /* Seek succeeded */
}




/*-----------------------------------------------------------------------*/
/* Directory handling - Move directory index next                        */
/*-----------------------------------------------------------------------*/

static
FRESULT dir_next (    /* FR_OK:Succeeded, FR_NO_FILE:End of table */
    FATDIR *dj            /* Pointer to directory object */
) {
    CLUST clst;
    WORD i;
    FATFS *fs = FatFs;


    i = dj->index + 1;
    if (!i || !dj->sect)    /* Report EOT when index has reached 65535 */
        return FR_NO_FILE;

    if (!(i & (16-1))) {    /* Sector changed? */
        dj->sect++;            /* Next sector */

        if (dj->clust == 0) {    /* Static table */
            if (i >= fs->n_rootdir)    /* Report EOT when end of table */
                return FR_NO_FILE;
        } else {                   /* Dynamic table */
            if (((i / 16) & (fs->csize-1)) == 0) {    /* Cluster changed? */
                clst = get_fat(dj->clust);        /* Get next cluster */
                if (clst <= 1) return FR_DISK_ERR;
                if (clst >= fs->max_clust)        /* When it reached end of dynamic table */
                    return FR_NO_FILE;            /* Report EOT */
                dj->clust = clst;                /* Initialize data for new cluster */
                dj->sect = clust2sect(clst);
            }
        }
    }

    dj->index = i;

    return FR_OK;
}




/*-----------------------------------------------------------------------*/
/* Directory handling - Find an object in the directory                  */
/*-----------------------------------------------------------------------*/

static
FRESULT dir_find (
    FATDIR *dj            /* Pointer to the directory object linked to the file name */
) {
    FRESULT res;
    BYTE c, *dir;


    res = dir_rewind(dj);            /* Rewind directory object */
    if (res != FR_OK) return res;

    dir = FatFs->buf;
    do {
        res = disk_readp(dir, dj->sect, (WORD)((dj->index % 16) * 32), 32)    /* Read an entry */
              ? FR_DISK_ERR : FR_OK;
        if (res != FR_OK) break;
        c = dir[DIR_Name];    /* First character */
        if (c == 0) {
            res = FR_NO_FILE;    /* Reached to end of table */
            break;
        }
        if (!(dir[DIR_Attr] & AM_VOL) && !mem_cmp(dir, dj->fn, 11)) /* Is it a valid entry? */
            break;
        res = dir_next(dj);                            /* Next entry */
    } while (res == FR_OK);

    return res;
}




/*-----------------------------------------------------------------------*/
/* Read an object from the directory                                     */
/*-----------------------------------------------------------------------*/
#if _USE_DIR
static
FRESULT dir_read (
    FATDIR *dj            /* Pointer to the directory object to store read object name */
) {
    FRESULT res;
    BYTE a, c, *dir;


    res = FR_NO_FILE;
    dir = FatFs->buf;
    while (dj->sect) {
        res = disk_readp(dir, dj->sect, (WORD)((dj->index % 16) * 32), 32)    /* Read an entry */
              ? FR_DISK_ERR : FR_OK;
        if (res != FR_OK) break;
        c = dir[DIR_Name];
        if (c == 0) {
            res = FR_NO_FILE;    /* Reached to end of table */
            break;
        }
        a = dir[DIR_Attr] & AM_MASK;
        if (c != 0xE5 && c != '.' && !(a & AM_VOL))    /* Is it a valid entry? */
            break;
        res = dir_next(dj);                /* Next entry */
        if (res != FR_OK) break;
    }

    if (res != FR_OK) dj->sect = 0;

    return res;
}
#endif



/*-----------------------------------------------------------------------*/
/* Pick a segment and create the object name in directory form           */
/*-----------------------------------------------------------------------*/

#ifdef _EXCVT
static const BYTE cvt[] = _EXCVT;
#endif

static
FRESULT create_name (
    FATDIR *dj,            /* Pointer to the directory object */
    const char **path    /* Pointer to pointer to the segment in the path string */
) {
    BYTE c, d, ni, si, i, *sfn;
    const char *p;

    /* Create file name in directory form */
    sfn = dj->fn;
    mem_set(sfn, ' ', 11);
    si = i = 0;
    ni = 8;
    p = *path;
    for (;;) {
        c = p[si++];
        if (c <= ' ' || c == '/') break;    /* Break on end of segment */
        if (c == '.' || i >= ni) {
            if (ni != 8 || c != '.') break;
            i = 8;
            ni = 11;
            continue;
        }
#ifdef _EXCVT
        if (c >= 0x80)                    /* To upper extended char (SBCS) */
            c = cvt[c - 0x80];
#endif
        if (IsDBCS1(c) && i >= ni - 1) {    /* DBC 1st byte? */
            d = p[si++];                    /* Get 2nd byte */
            sfn[i++] = c;
            sfn[i++] = d;
        } else {                        /* Single byte code */
            if (IsLower(c)) c -= 0x20;    /* toupper */
            sfn[i++] = c;
        }
    }
    *path = &p[si];                        /* Rerurn pointer to the next segment */

    sfn[11] = (c <= ' ') ? 1 : 0;        /* Set last segment flag if end of path */

    return FR_OK;
}




/*-----------------------------------------------------------------------*/
/* Get file information from directory entry                             */
/*-----------------------------------------------------------------------*/
#if _USE_DIR
static
void get_fileinfo (        /* No return code */
    FATDIR *dj,            /* Pointer to the directory object */
    FILINFO *fno         /* Pointer to store the file information */
) {
    BYTE i, c, *dir;
    char *p;


    p = fno->fname;
    if (dj->sect) {
        dir = FatFs->buf;
        for (i = 0; i < 8; i++) {    /* Copy file name body */
            c = dir[i];
            if (c == ' ') break;
            if (c == 0x05) c = 0xE5;
            *p++ = c;
        }
        if (dir[8] != ' ') {        /* Copy file name extension */
            *p++ = '.';
            for (i = 8; i < 11; i++) {
                c = dir[i];
                if (c == ' ') break;
                *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;
}
#endif /* _USE_DIR */



/*-----------------------------------------------------------------------*/
/* Follow a file path                                                    */
/*-----------------------------------------------------------------------*/

static
FRESULT follow_path (    /* FR_OK(0): successful, !=0: error code */
    FATDIR *dj,            /* Directory object to return last directory and found object */
    const char *path    /* Full-path string to find a file or directory */
) {
    FRESULT res;
    BYTE *dir;


    while (*path == ' ') path++;        /* Skip leading spaces */
    if (*path == '/') path++;            /* Strip heading separator */
    dj->sclust = 0;                        /* Set start directory (always root dir) */

    if ((BYTE)*path <= ' ') {            /* Null path means the root directory */
        res = dir_rewind(dj);
        FatFs->buf[0] = 0;

    } else {                            /* Follow path */
        for (;;) {
            res = create_name(dj, &path);    /* Get a segment */
            if (res != FR_OK) break;
            res = dir_find(dj);                /* Find it */
            if (res != FR_OK) {                /* Could not find the object */
                if (res == FR_NO_FILE && !*(dj->fn+11))
                    res = FR_NO_PATH;
                break;
            }
            if (*(dj->fn+11)) break;        /* Last segment match. Function completed. */
            dir = FatFs->buf;                /* There is next segment. Follow the sub directory */
            if (!(dir[DIR_Attr] & AM_DIR)) { /* Cannot follow because it is a file */
                res = FR_NO_PATH;
                break;
            }
            dj->sclust =
#if _FS_FAT32
                ((DWORD)LD_WORD(dir+DIR_FstClusHI) << 16) |
#endif
                LD_WORD(dir+DIR_FstClusLO);
        }
    }

    return res;
}




/*-----------------------------------------------------------------------*/
/* Check a sector if it is an FAT boot record                            */
/*-----------------------------------------------------------------------*/

static
__attribute__((section(".SD_Code"))) BYTE check_fs (    /* 0:The FAT boot record, 1:Valid boot record but not an FAT, 2:Not a boot record, 3:Error */
    BYTE *buf,    /* Working buffer */
    DWORD sect    /* Sector# (lba) to check if it is an FAT boot record or not */
) {
    if (disk_readp(buf, sect, 510, 2))        /* Read the boot sector */
        return 3;
    if (LD_WORD(buf) != 0xAA55)                /* Check record signature */
        return 2;

    if (!disk_readp(buf, sect, BS_FilSysType, 2) && LD_WORD(buf) == 0x4146)    /* Check FAT12/16 */
        return 0;
#if _FS_FAT32
    if (!disk_readp(buf, sect, BS_FilSysType32, 2) && LD_WORD(buf) == 0x4146)    /* Check FAT32 */
        return 0;
#endif
    return 1;
}




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

   Public Functions

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



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

__attribute__((section(".SD_Code"))) FRESULT pf_mount (
    FATFS *fs        /* Pointer to new file system object (NULL: Unmount) */
) {
    BYTE fmt, buf[36];
    DWORD bsect, fsize, tsect, mclst;


    FatFs = 0;
    if (!fs) return FR_OK;                /* Unregister fs object */

    if (disk_initialize() & STA_NOINIT)    /* Check if the drive is ready or not */
        return FR_NOT_READY;

    /* Search FAT partition on the drive */
    bsect = 0;
    fmt = check_fs(buf, bsect);            /* Check sector 0 as an SFD format */
    if (fmt == 1) {                        /* Not an FAT boot record, it may be FDISK format */
        /* Check a partition listed in top of the partition table */
        if (disk_readp(buf, bsect, MBR_Table, 16)) {    /* 1st partition entry */
            fmt = 3;
        } else {
            if (buf[4]) {                    /* Is the partition existing? */
                bsect = LD_DWORD(&buf[8]);    /* Partition offset in LBA */
                fmt = check_fs(buf, bsect);    /* Check the partition */
            }
        }
    }
    if (fmt == 3) return FR_DISK_ERR;
    if (fmt) return FR_NO_FILESYSTEM;    /* No valid FAT patition is found */

    /* Initialize the file system object */
    if (disk_readp(buf, bsect, 13, sizeof(buf))) return FR_DISK_ERR;

    fsize = LD_WORD(buf+BPB_FATSz16-13);                /* Number of sectors per FAT */
    if (!fsize) fsize = LD_DWORD(buf+BPB_FATSz32-13);

    fsize *= buf[BPB_NumFATs-13];                        /* Number of sectors in FAT area */
    fs->fatbase = bsect + LD_WORD(buf+BPB_RsvdSecCnt-13); /* FAT start sector (lba) */
    fs->csize = buf[BPB_SecPerClus-13];                    /* Number of sectors per cluster */
    fs->n_rootdir = LD_WORD(buf+BPB_RootEntCnt-13);        /* Nmuber of root directory entries */
    tsect = LD_WORD(buf+BPB_TotSec16-13);                /* Number of sectors on the file system */
    if (!tsect) tsect = LD_DWORD(buf+BPB_TotSec32-13);
    mclst = (tsect                        /* Last cluster# + 1 */
             - LD_WORD(buf+BPB_RsvdSecCnt-13) - fsize - fs->n_rootdir / 16
            ) / fs->csize + 2;
    fs->max_clust = (CLUST)mclst;

    fmt = FS_FAT12;                            /* Determine the FAT sub type */
    if (mclst >= 0xFF7) fmt = FS_FAT16;        /* Number of clusters >= 0xFF5 */
    if (mclst >= 0xFFF7)                    /* Number of clusters >= 0xFFF5 */
#if _FS_FAT32
        fmt = FS_FAT32;
#else
        return FR_NO_FILESYSTEM;
#endif

    fs->fs_type = fmt;        /* FAT sub-type */
#if _FS_FAT32
    if (fmt == FS_FAT32)
        fs->dirbase = LD_DWORD(buf+(BPB_RootClus-13));    /* Root directory start cluster */
    else
#endif
        fs->dirbase = fs->fatbase + fsize;                /* Root directory start sector (lba) */
    fs->database = fs->fatbase + fsize + fs->n_rootdir / 16;    /* Data start sector (lba) */

    fs->flag = 0;
    FatFs = fs;

    return FR_OK;
}




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

FRESULT pf_open (
    const char *path    /* Pointer to the file name */
) {
    FRESULT res;
    FATDIR dj;
    BYTE sp[12], dir[32];
    FATFS *fs = FatFs;


    if (!fs)                        /* Check file system */
        return FR_NOT_ENABLED;

    fs->flag = 0;
    fs->buf = dir;
    dj.fn = sp;
    res = follow_path(&dj, path);    /* Follow the file path */
    if (res != FR_OK) return res;    /* Follow failed */
    if (!dir[0] || (dir[DIR_Attr] & AM_DIR))    /* It is a directory */
        return FR_NO_FILE;

    fs->org_clust =                        /* File start cluster */
#if _FS_FAT32
        ((DWORD)LD_WORD(dir+DIR_FstClusHI) << 16) |
#endif
        LD_WORD(dir+DIR_FstClusLO);
    fs->fsize = LD_DWORD(dir+DIR_FileSize);    /* File size */
    fs->fptr = 0;                        /* File pointer */
    fs->flag = FA_OPENED;

    return FR_OK;
}




/*-----------------------------------------------------------------------*/
/* Read File                                                             */
/*-----------------------------------------------------------------------*/
#if _USE_READ

FRESULT pf_read (
    void* buff,        /* Pointer to the read buffer (NULL:Forward data to the stream)*/
    WORD btr,        /* Number of bytes to read */
    WORD* br        /* Pointer to number of bytes read */
) {
    DRESULT dr;
    CLUST clst;
    DWORD sect, remain;
    BYTE *rbuff = (BYTE *)buff;
    WORD rcnt;
    FATFS *fs = FatFs;


    *br = 0;
    if (!fs) return FR_NOT_ENABLED;        /* Check file system */
    if (!(fs->flag & FA_OPENED))        /* Check if opened */
        return FR_NOT_OPENED;

    remain = fs->fsize - fs->fptr;
    if (btr > remain) btr = (WORD)remain;            /* Truncate btr by remaining bytes */

    while (btr)    {                                    /* Repeat until all data transferred */
        if ((fs->fptr % 512) == 0) {                /* On the sector boundary? */
            if ((fs->fptr / 512 % fs->csize) == 0) {    /* On the cluster boundary? */
                clst = (fs->fptr == 0) ?            /* On the top of the file? */
                       fs->org_clust : get_fat(fs->curr_clust);
                if (clst <= 1) goto fr_abort;
                fs->curr_clust = clst;                /* Update current cluster */
                fs->csect = 0;                        /* Reset sector offset in the cluster */
            }
            sect = clust2sect(fs->curr_clust);        /* Get current sector */
            if (!sect) goto fr_abort;
            fs->dsect = sect + fs->csect++;
        }
        rcnt = 512 - ((WORD)fs->fptr % 512);        /* Get partial sector data from sector buffer */
        if (rcnt > btr) rcnt = btr;
        dr = disk_readp(!buff ? 0 : rbuff, fs->dsect, (WORD)(fs->fptr % 512), rcnt);
        if (dr) goto fr_abort;
        fs->fptr += rcnt;
        rbuff += rcnt;            /* Update pointers and counters */
        btr -= rcnt;
        *br += rcnt;
    }

    return FR_OK;

fr_abort:
    fs->flag = 0;
    return FR_DISK_ERR;
}
#endif



/*-----------------------------------------------------------------------*/
/* Write File                                                            */
/*-----------------------------------------------------------------------*/
#if _USE_WRITE

FRESULT pf_write (
    const void* buff,    /* Pointer to the data to be written */
    WORD btw,            /* Number of bytes to write (0:Finalize the current write operation) */
    WORD* bw            /* Pointer to number of bytes written */
) {
    CLUST clst;
    DWORD sect, remain;
    const BYTE *p = (const BYTE *)buff;
    WORD wcnt;
    FATFS *fs = FatFs;


    *bw = 0;
    if (!fs) return FR_NOT_ENABLED;        /* Check file system */
    if (!(fs->flag & FA_OPENED))        /* Check if opened */
        return FR_NOT_OPENED;

    if (!btw) {        /* Finalize request */
        if ((fs->flag & FA__WIP) && disk_writep(0, 0)) goto fw_abort;
        fs->flag &= ~FA__WIP;
        return FR_OK;
    } else {        /* Write data request */
        if (!(fs->flag & FA__WIP))        /* Round down fptr to the sector boundary */
            fs->fptr &= 0xFFFFFE00;
    }
    remain = fs->fsize - fs->fptr;
    if (btw > remain) btw = (WORD)remain;            /* Truncate btw by remaining bytes */

    while (btw)    {                                    /* Repeat until all data transferred */
        if (((WORD)fs->fptr % 512) == 0) {                /* On the sector boundary? */
            if ((fs->fptr / 512 % fs->csize) == 0) {    /* On the cluster boundary? */
                clst = (fs->fptr == 0) ?            /* On the top of the file? */
                       fs->org_clust : get_fat(fs->curr_clust);
                if (clst <= 1) goto fw_abort;
                fs->curr_clust = clst;                /* Update current cluster */
                fs->csect = 0;                        /* Reset sector offset in the cluster */
            }
            sect = clust2sect(fs->curr_clust);        /* Get current sector */
            if (!sect) goto fw_abort;
            fs->dsect = sect + fs->csect++;
            if (disk_writep(0, fs->dsect)) goto fw_abort;    /* Initiate a sector write operation */
            fs->flag |= FA__WIP;
        }
        wcnt = 512 - ((WORD)fs->fptr % 512);        /* Number of bytes to write to the sector */
        if (wcnt > btw) wcnt = btw;
        if (disk_writep(p, wcnt)) goto fw_abort;    /* Send data to the sector */
        fs->fptr += wcnt;
        p += wcnt;                /* Update pointers and counters */
        btw -= wcnt;
        *bw += wcnt;
        if (((WORD)fs->fptr % 512) == 0) {
            if (disk_writep(0, 0)) goto fw_abort;    /* Finalize the currtent secter write operation */
            fs->flag &= ~FA__WIP;
        }
    }

    return FR_OK;

fw_abort:
    fs->flag = 0;
    return FR_DISK_ERR;
}
#endif



/*-----------------------------------------------------------------------*/
/* Seek File R/W Pointer                                                 */
/*-----------------------------------------------------------------------*/
#if _USE_LSEEK

FRESULT pf_lseek (
    DWORD ofs        /* File pointer from top of file */
) {
    CLUST clst;
    DWORD bcs, sect, ifptr;
    FATFS *fs = FatFs;


    if (!fs) return FR_NOT_ENABLED;        /* Check file system */
    if (!(fs->flag & FA_OPENED))        /* Check if opened */
        return FR_NOT_OPENED;

    if (ofs > fs->fsize) ofs = fs->fsize;    /* Clip offset with the file size */
    ifptr = fs->fptr;
    fs->fptr = 0;
    if (ofs > 0) {
        bcs = (DWORD)fs->csize * 512;    /* Cluster size (byte) */
        if (ifptr > 0 &&
                (ofs - 1) / bcs >= (ifptr - 1) / bcs) {    /* When seek to same or following cluster, */
            fs->fptr = (ifptr - 1) & ~(bcs - 1);    /* start from the current cluster */
            ofs -= fs->fptr;
            clst = fs->curr_clust;
        } else {                            /* When seek to back cluster, */
            clst = fs->org_clust;            /* start from the first cluster */
            fs->curr_clust = clst;
        }
        while (ofs > bcs) {                /* Cluster following loop */
            clst = get_fat(clst);        /* Follow cluster chain */
            if (clst <= 1 || clst >= fs->max_clust) goto fe_abort;
            fs->curr_clust = clst;
            fs->fptr += bcs;
            ofs -= bcs;
        }
        fs->fptr += ofs;
        sect = clust2sect(clst);        /* Current sector */
        if (!sect) goto fe_abort;
        fs->csect = (BYTE)(ofs / 512);    /* Sector offset in the cluster */
        if (ofs % 512)
            fs->dsect = sect + fs->csect++;
    }

    return FR_OK;

fe_abort:
    fs->flag = 0;
    return FR_DISK_ERR;
}
#endif



/*-----------------------------------------------------------------------*/
/* Create a Directroy Object                                             */
/*-----------------------------------------------------------------------*/
#if _USE_DIR

FRESULT pf_opendir (
    FATDIR *dj,            /* Pointer to directory object to create */
    const char *path    /* Pointer to the directory path */
) {
    FRESULT res;
    BYTE sp[12], dir[32];
    FATFS *fs = FatFs;


    if (!fs) {                /* Check file system */
        res = FR_NOT_ENABLED;
    } else {
        fs->buf = dir;
        dj->fn = sp;
        res = follow_path(dj, path);            /* Follow the path to the directory */
        if (res == FR_OK) {                        /* Follow completed */
            if (dir[0]) {                        /* It is not the root dir */
                if (dir[DIR_Attr] & AM_DIR) {    /* The object is a directory */
                    dj->sclust =
#if _FS_FAT32
                        ((DWORD)LD_WORD(dir+DIR_FstClusHI) << 16) |
#endif
                        LD_WORD(dir+DIR_FstClusLO);
                } else {                        /* The object is not a directory */
                    res = FR_NO_PATH;
                }
            }
            if (res == FR_OK)
                res = dir_rewind(dj);            /* Rewind dir */
        }
        if (res == FR_NO_FILE) res = FR_NO_PATH;
    }

    return res;
}




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

FRESULT pf_readdir (
    FATDIR *dj,            /* Pointer to the open directory object */
    FILINFO *fno        /* Pointer to file information to return */
) {
    FRESULT res;
    BYTE sp[12], dir[32];
    FATFS *fs = FatFs;


    if (!fs) {                /* Check file system */
        res = FR_NOT_ENABLED;
    } else {
        fs->buf = dir;
        dj->fn = sp;
        if (!fno) {
            res = dir_rewind(dj);
        } else {
            res = dir_read(dj);
            if (res == FR_NO_FILE) {
                dj->sect = 0;
                res = FR_OK;
            }
            if (res == FR_OK) {                /* A valid entry is found */
                get_fileinfo(dj, fno);        /* Get the object information */
                res = dir_next(dj);            /* Increment index for next */
                if (res == FR_NO_FILE) {
                    dj->sect = 0;
                    res = FR_OK;
                }
            }
        }
    }

    return res;
}

#endif /* _USE_DIR */