lfn.c

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/* lfn.c  -  Functions for handling VFAT long filenames */

/* Written 1998 by Roman Hodek */

#include "vfatlib.h"

#define NDEBUG
#include <debug.h>

typedef struct {
    __u8    id;     /* sequence number for slot */
    __u8    name0_4[10];    /* first 5 characters in name */
    __u8    attr;       /* attribute byte */
    __u8    reserved;   /* always 0 */
    __u8    alias_checksum; /* checksum for 8.3 alias */
    __u8    name5_10[12];   /* 6 more characters in name */
    __u16   start;      /* starting cluster number, 0 in long slots */
    __u8    name11_12[4];   /* last 2 characters in name */
} LFN_ENT;

#define LFN_ID_START    0x40
#define LFN_ID_SLOTMASK 0x1f

#define CHARS_PER_LFN   13

/* These modul-global vars represent the state of the LFN parser */
unsigned char *lfn_unicode = NULL;
unsigned char lfn_checksum;
int lfn_slot = -1;
loff_t *lfn_offsets = NULL;
int lfn_parts = 0;

static unsigned char fat_uni2esc[64] = {
    '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
    'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
    'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
    'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
    'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
    'u', 'v', 'w', 'x', 'y', 'z', '+', '-'
};

/* This defines which unicode chars are directly convertable to ISO-8859-1 */
#define UNICODE_CONVERTABLE(cl,ch)  (ch == 0 && (cl < 0x80 || cl >= 0xa0))

/* for maxlen param */
#define UNTIL_0     INT_MAX

static void copy_lfn_part( char *dst, LFN_ENT *lfn );
static char *cnv_unicode( const unsigned char *uni, int maxlen, int use_q );

/* Convert name part in 'lfn' from unicode to ASCII */
static __inline char* CNV_THIS_PART(LFN_ENT *lfn)
{                           \
    char __part_uni[CHARS_PER_LFN*2];
    copy_lfn_part( __part_uni, lfn );
    return cnv_unicode( (unsigned char*)__part_uni, CHARS_PER_LFN, 0 );
}

/* Convert name parts collected so far (from previous slots) from unicode to
 * ASCII */
#define CNV_PARTS_SO_FAR()                  \
    (cnv_unicode( lfn_unicode+(lfn_slot*CHARS_PER_LFN*2),   \
              lfn_parts*CHARS_PER_LFN, 0 ))

/* This function converts an unicode string to a normal ASCII string, assuming
 * ISO-8859-1 charset. Characters not in 8859-1 are converted to the same
 * escape notation as used by the kernel, i.e. the uuencode-like ":xxx" */
static char *cnv_unicode( const unsigned char *uni, int maxlen, int use_q )
{
    const unsigned char *up;
    unsigned char *out, *cp;
    int len, val;

    for( len = 0, up = uni; (up-uni)/2 < maxlen && (up[0] || up[1]); up += 2 ){
    if (UNICODE_CONVERTABLE(up[0],up[1]))
        ++len;
    else
        len += 4;
    }
    cp = out = use_q ? qalloc( &FsCheckMemQueue, len+1 ) : vfalloc( len+1 );

    for( up = uni; (up-uni)/2 < maxlen && (up[0] || up[1]); up += 2 ) {
    if (UNICODE_CONVERTABLE(up[0],up[1]))
        *cp++ = up[0];
    else {
        /* here the same escape notation is used as in the Linux kernel */
        *cp++ = ':';
        val = (up[1] << 8) + up[0];
        cp[2] = fat_uni2esc[val & 0x3f];
        val >>= 6;
        cp[1] = fat_uni2esc[val & 0x3f];
        val >>= 6;
        cp[0] = fat_uni2esc[val & 0x3f];
        cp += 3;
    }
    }
    *cp = 0;

    return (char *)out;
}


static void copy_lfn_part( char *dst, LFN_ENT *lfn )
{
    memcpy( dst,    lfn->name0_4,   10 );
    memcpy( dst+10, lfn->name5_10,  12 );
    memcpy( dst+22, lfn->name11_12, 4 );
}


static void clear_lfn_slots( int start, int end )
{
    int i;
    LFN_ENT empty;

    /* New dir entry is zeroed except first byte, which is set to 0xe5.
     * This is to avoid that some FAT-reading OSes (not Linux! ;) stop reading
     * a directory at the first zero entry...
     */
    memset( &empty, 0, sizeof(empty) );
    empty.id = DELETED_FLAG;

    for( i = start; i <= end; ++i ) {
    fs_write( lfn_offsets[i], sizeof(LFN_ENT), &empty );
    }
}

void lfn_reset( void )
{
    if (lfn_unicode)
    vffree( lfn_unicode );
    lfn_unicode = NULL;
    if (lfn_offsets)
    vffree( lfn_offsets );
    lfn_offsets = NULL;
    lfn_slot = -1;
}


/* This function is only called with de->attr == VFAT_LN_ATTR. It stores part
 * of the long name. */
void lfn_add_slot( DIR_ENT *de, loff_t dir_offset )
{
    LFN_ENT *lfn = (LFN_ENT *)de;
    unsigned offset;

    if (de->attr != VFAT_LN_ATTR)
    die("lfn_add_slot called with non-LFN directory entry");

    if (lfn->id & LFN_ID_START) {
    if (lfn_slot != -1) {
        int can_clear = 0;
        /* There is already a LFN "in progess", so it is an error that a
         * new start entry is here. */
        /* Causes: 1) if slot# == expected: start bit set mysteriously, 2)
         *         old LFN overwritten by new one */
        /* Fixes: 1) delete previous LFN 2) if slot# == expected and
         *        checksum ok: clear start bit */
        /* XXX: Should delay that until next LFN known (then can better
         * display the name) */
        VfatPrint( "A new long file name starts within an old one.\n" );
        if ((lfn->id & LFN_ID_SLOTMASK) == lfn_slot &&
        lfn->alias_checksum == lfn_checksum) {
        char *part1 = CNV_THIS_PART(lfn);
        char *part2 = CNV_PARTS_SO_FAR();
        VfatPrint( "  It could be that the LFN start bit is wrong here\n"
            "  if \"%s\" seems to match \"%s\".\n", part1, part2 );
        vffree( part1 );
        vffree( part2 );
        can_clear = 1;
        }
        if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete previous LFN\n2: Leave it as it is.\n" );
        if (can_clear)
            VfatPrint( "3: Clear start bit and concatenate LFNs\n" );
        }
        else VfatPrint( "  Not auto-correcting this.\n" );
        if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( can_clear ? "123" : "12", "?" )) {
          case '1':
            clear_lfn_slots( 0, lfn_parts-1 );
            lfn_reset();
            break;
          case '2':
            break;
          case '3':
            lfn->id &= ~LFN_ID_START;
            fs_write( dir_offset+offsetof(LFN_ENT,id),
                  sizeof(lfn->id), &lfn->id );
            break;
        }
        }
    }
    lfn_slot = lfn->id & LFN_ID_SLOTMASK;
    lfn_checksum = lfn->alias_checksum;
    lfn_unicode = vfalloc( (lfn_slot*CHARS_PER_LFN+1)*2 );
    lfn_offsets = vfalloc( lfn_slot*sizeof(loff_t) );
    lfn_parts = 0;
    }
    else if (lfn_slot == -1) {
    /* No LFN in progress, but slot found; start bit missing */
    /* Causes: 1) start bit got lost, 2) Previous slot with start bit got
     *         lost */
    /* Fixes: 1) delete LFN, 2) set start bit */
    char *part = CNV_THIS_PART(lfn);
    VfatPrint( "Long filename fragment \"%s\" found outside a LFN "
        "sequence.\n  (Maybe the start bit is missing on the "
        "last fragment)\n", part );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete fragment\n2: Leave it as it is.\n"
            "3: Set start bit\n" );
    }
    else VfatPrint( "  Not auto-correcting this.\n" );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( "123", "?" )) {
          case '1':
        if (!lfn_offsets)
            lfn_offsets = vfalloc( sizeof(loff_t) );
        lfn_offsets[0] = dir_offset;
        clear_lfn_slots( 0, 0 );
        lfn_reset();
        return;
          case '2':
        lfn_reset();
        return;
          case '3':
        lfn->id |= LFN_ID_START;
        fs_write( dir_offset+offsetof(LFN_ENT,id),
              sizeof(lfn->id), &lfn->id );
        lfn_slot = lfn->id & LFN_ID_SLOTMASK;
        lfn_checksum = lfn->alias_checksum;
        lfn_unicode = vfalloc( (lfn_slot*CHARS_PER_LFN+1)*2 );
        lfn_offsets = vfalloc( lfn_slot*sizeof(loff_t) );
        lfn_parts = 0;
        break;
        }
    }
    }
    else if ((lfn->id & LFN_ID_SLOTMASK) != lfn_slot) {
    /* wrong sequence number */
    /* Causes: 1) seq-no destroyed */
    /* Fixes: 1) delete LFN, 2) fix number (maybe only if following parts
     *        are ok?, maybe only if checksum is ok?) (Attention: space
     *        for name was allocated before!) */
    int can_fix = 0;
    VfatPrint( "Unexpected long filename sequence number "
        "(%d vs. expected %d).\n",
        (lfn->id & LFN_ID_SLOTMASK), lfn_slot );
    if (lfn->alias_checksum == lfn_checksum) {
        char *part1 = CNV_THIS_PART(lfn);
        char *part2 = CNV_PARTS_SO_FAR();
        VfatPrint( "  It could be that just the number is wrong\n"
            "  if \"%s\" seems to match \"%s\".\n", part1, part2 );
        vffree( part1 );
        vffree( part2 );
        can_fix = 1;
    }
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete LFN\n2: Leave it as it is (and ignore LFN so far)\n" );
        if (can_fix)
        VfatPrint( "3: Correct sequence number\n" );
    }
    else VfatPrint( "  Not auto-correcting this.\n" );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( can_fix ? "123" : "12", "?" )) {
          case '1':
        lfn_offsets[lfn_parts++] = dir_offset;
        clear_lfn_slots( 0, lfn_parts-1 );
        lfn_reset();
        return;
          case '2':
        lfn_reset();
        return;
          case '3':
        lfn->id = (lfn->id & ~LFN_ID_SLOTMASK) | lfn_slot;
        fs_write( dir_offset+offsetof(LFN_ENT,id),
              sizeof(lfn->id), &lfn->id );
        break;
        }
    }
    }

    if (lfn->alias_checksum != lfn_checksum) {
    /* checksum mismatch */
    /* Causes: 1) checksum field here destroyed */
    /* Fixes: 1) delete LFN, 2) fix checksum */
    VfatPrint( "Checksum in long filename part wrong "
        "(%02x vs. expected %02x).\n",
        lfn->alias_checksum, lfn_checksum );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete LFN\n2: Leave it as it is.\n"
            "3: Correct checksum\n" );
    }
    else VfatPrint( "  Not auto-correcting this.\n" );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( "123", "?" )) {
          case '1':
        lfn_offsets[lfn_parts++] = dir_offset;
        clear_lfn_slots( 0, lfn_parts-1 );
        lfn_reset();
        return;
          case '2':
        break;
          case '3':
        lfn->alias_checksum = lfn_checksum;
        fs_write( dir_offset+offsetof(LFN_ENT,alias_checksum),
              sizeof(lfn->alias_checksum), &lfn->alias_checksum );
        break;
        }
    }
    }

    if (lfn_slot != -1) {
    lfn_slot--;
    offset = lfn_slot * CHARS_PER_LFN*2;
    copy_lfn_part( (char*)lfn_unicode+offset, lfn );
    if (lfn->id & LFN_ID_START)
        lfn_unicode[offset+26] = lfn_unicode[offset+27] = 0;
    lfn_offsets[lfn_parts++] = dir_offset;
    }

    if (lfn->reserved != 0) {
    VfatPrint( "Reserved field in VFAT long filename slot is not 0 "
        "(but 0x%02x).\n", lfn->reserved );
    if (FsCheckFlags & FSCHECK_INTERACTIVE)
        VfatPrint( "1: Fix.\n2: Leave it.\n" );
    else VfatPrint( "Auto-setting to 0.\n" );
    if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1') {
        lfn->reserved = 0;
        fs_write( dir_offset+offsetof(LFN_ENT,reserved),
              sizeof(lfn->reserved), &lfn->reserved );
    }
    }
    if (lfn->start != CT_LE_W(0)) {
    VfatPrint( "Start cluster field in VFAT long filename slot is not 0 "
        "(but 0x%04x).\n", lfn->start );
    if (FsCheckFlags & FSCHECK_INTERACTIVE)
        VfatPrint( "1: Fix.\n2: Leave it.\n" );
    else VfatPrint( "Auto-setting to 0.\n" );
    if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1') {
        lfn->start = CT_LE_W(0);
        fs_write( dir_offset+offsetof(LFN_ENT,start),
              sizeof(lfn->start),&lfn->start );
    }
    }
}


/* This function is always called when de->attr != VFAT_LN_ATTR is found, to
 * retrieve the previously constructed LFN. */
char *lfn_get( DIR_ENT *de )
{
    char *lfn;
    __u8 sum;
    int i;

    if (de->attr == VFAT_LN_ATTR)
    die("lfn_get called with LFN directory entry");

#if 0
    if (de->lcase)
    VfatPrint( "lcase=%02x\n",de->lcase );
#endif

    if (lfn_slot == -1)
    /* no long name for this file */
    return NULL;

    if (lfn_slot != 0) {
    /* The long name isn't finished yet. */
    /* Causes: 1) LFN slot overwritten by non-VFAT aware tool */
    /* Fixes: 1) delete LFN 2) move overwriting entry to somewhere else
     * and let user enter missing part of LFN (hard to do :-()
     * 3) renumber entries and truncate name */
    char *long_name = CNV_PARTS_SO_FAR();
    char *short_name = file_name(de->name);
    VfatPrint( "Unfinished long file name \"%s\".\n"
        "  (Start may have been overwritten by %s)\n",
        long_name, short_name );
    vffree( long_name );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete LFN\n2: Leave it as it is.\n"
            "3: Fix numbering (truncates long name and attaches "
            "it to short name %s)\n", short_name );
    }
    else VfatPrint( "  Not auto-correcting this.\n" );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( "123", "?" )) {
          case '1':
        clear_lfn_slots( 0, lfn_parts-1 );
        lfn_reset();
        return NULL;
          case '2':
        lfn_reset();
        return NULL;
          case '3':
        for( i = 0; i < lfn_parts; ++i ) {
            __u8 id = (lfn_parts-i) | (i==0 ? LFN_ID_START : 0);
            fs_write( lfn_offsets[i]+offsetof(LFN_ENT,id),
                  sizeof(id), &id );
        }
        memmove( lfn_unicode, lfn_unicode+lfn_slot*CHARS_PER_LFN*2,
             lfn_parts*CHARS_PER_LFN*2 );
        break;
        }
    }
    }

    for (sum = 0, i = 0; i < 8; i++)
    sum = (((sum&1) << 7) | ((sum&0xfe) >> 1)) + de->name[i];

    for (i = 0; i < 3; i++)
    sum = (((sum&1) << 7) | ((sum&0xfe) >> 1)) + de->ext[i];

    if (sum != lfn_checksum) {
    /* checksum doesn't match, long name doesn't apply to this alias */
    /* Causes: 1) alias renamed */
    /* Fixes: 1) Fix checksum in LFN entries */
    char *long_name = CNV_PARTS_SO_FAR();
    char *short_name = file_name(de->name);
    VfatPrint( "Wrong checksum for long file name \"%s\".\n"
        "  (Short name %s may have changed without updating the long name)\n",
        long_name, short_name );
    vffree( long_name );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        VfatPrint( "1: Delete LFN\n2: Leave it as it is.\n"
            "3: Fix checksum (attaches to short name %s)\n",
            short_name );
    }
    else VfatPrint( "  Not auto-correcting this.\n" );
    if (FsCheckFlags & FSCHECK_INTERACTIVE) {
        switch( get_key( "123", "?" )) {
          case '1':
        clear_lfn_slots( 0, lfn_parts-1 );
        lfn_reset();
        return NULL;
          case '2':
        lfn_reset();
        return NULL;
          case '3':
        for( i = 0; i < lfn_parts; ++i ) {
            fs_write( lfn_offsets[i]+offsetof(LFN_ENT,alias_checksum),
                  sizeof(sum), &sum );
        }
        break;
        }
    }
    }

    lfn = cnv_unicode( lfn_unicode, UNTIL_0, 1 );
    lfn_reset();
    return( lfn );
}

void lfn_check_orphaned(void)
{
    char *long_name;

    if (lfn_slot == -1)
    return;

    long_name = CNV_PARTS_SO_FAR();
    VfatPrint("Orphaned long file name part \"%s\"\n", long_name);
    if (FsCheckFlags & FSCHECK_INTERACTIVE)
    VfatPrint( "1: Delete.\n2: Leave it.\n" );
    else VfatPrint( "  Auto-deleting.\n" );
    if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1') {
    clear_lfn_slots(0, lfn_parts - 1);
    }
    lfn_reset();
}

/* Local Variables: */
/* tab-width: 8     */
/* End:             */