/*      $OpenBSD: msdosfs_conv.c,v 1.3 2023/08/11 04:51:36 guenther Exp $       */
/*      $NetBSD: msdosfs_conv.c,v 1.24 1997/10/17 11:23:54 ws Exp $     */

/*-
 * Copyright (C) 1995, 1997 Wolfgang Solfrank.
 * Copyright (C) 1995, 1997 TooLs GmbH.
 * All rights reserved.
 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by TooLs GmbH.
 * 4. The name of TooLs GmbH may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*
 * Written by Paul Popelka (paulp@uts.amdahl.com)
 *
 * You can do anything you want with this software, just don't say you wrote
 * it, and don't remove this notice.
 *
 * This software is provided "as is".
 *
 * The author supplies this software to be publicly redistributed on the
 * understanding that the author is not responsible for the correct
 * functioning of this software in any circumstances and is not liable for
 * any damages caused by this software.
 *
 * October 1992
 */

/*
 * System include files.
 */
#include <sys/time.h>
#include <sys/dirent.h>
#include <sys/lock.h>

/*
 * MSDOSFS include files.
 */
#include "msdos/direntry.h"
#include "msdos/denode.h"

/*
 * Days in each month in a regular year.
 */
const u_short regyear[] = {
        31, 28, 31, 30, 31, 30,
        31, 31, 30, 31, 30, 31
};

/*
 * Days in each month in a leap year.
 */
const u_short leapyear[] = {
        31, 29, 31, 30, 31, 30,
        31, 31, 30, 31, 30, 31
};

/*
 * Variables used to remember parts of the last time conversion.  Maybe we
 * can avoid a full conversion.
 */
time_t lasttime;
uint32_t lastday;
u_short lastddate;
u_short lastdtime;

/*
 * Convert the unix version of time to dos's idea of time to be used in
 * file timestamps. The passed in unix time is assumed to be in GMT.
 */
void
unix2dostime(const struct timespec *tsp, int minuteswest, u_int16_t *ddp,
    u_int16_t *dtp, u_int8_t *dhp)
{
        time_t t;
        uint32_t days;
        uint32_t inc;
        uint32_t year;
        uint32_t month;
        const u_short *months;

        /*
         * If the time from the last conversion is the same as now, then
         * skip the computations and use the saved result.
         */
        t = tsp->tv_sec - (minuteswest * 60)
             /* +- daylight saving time correction */ ;
        t &= ~1;
        /*
         * Before 1/1/1980 there is only a timeless void. After 12/31/2107
         * there is only Cthulhu.
         */
#define DOSEPOCH 315532800LL
#define DOSENDTIME 4354775999LL
        if (t < DOSEPOCH || t > DOSENDTIME)
                t = DOSEPOCH;

        if (lasttime != t) {
                lasttime = t;
                lastdtime = (((t / 2) % 30) << DT_2SECONDS_SHIFT)
                    + (((t / 60) % 60) << DT_MINUTES_SHIFT)
                    + (((t / 3600) % 24) << DT_HOURS_SHIFT);

                /*
                 * If the number of days since 1970 is the same as the last
                 * time we did the computation then skip all this leap year
                 * and month stuff.
                 */
                days = t / (24 * 60 * 60);
                if (days != lastday) {
                        lastday = days;
                        for (year = 1970;; year++) {
                                inc = year & 0x03 ? 365 : 366;
                                if (days < inc)
                                        break;
                                days -= inc;
                        }
                        months = year & 0x03 ? regyear : leapyear;
                        for (month = 0; month < 12; month++) {
                                if (days < months[month])
                                        break;
                                days -= months[month];
                        }
                        lastddate = ((days + 1) << DD_DAY_SHIFT)
                            + ((month + 1) << DD_MONTH_SHIFT);
                        /*
                         * Remember dos's idea of time is relative to 1980.
                         * unix's is relative to 1970.  If somehow we get a
                         * time before 1980 then don't give totally crazy
                         * results.
                         */
                        if (year > 1980)
                                lastddate += (year - 1980) << DD_YEAR_SHIFT;
                }
        }

        if (dtp != NULL)
                *dtp = lastdtime;
        if (dhp != NULL)
                *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000;

        *ddp = lastddate;
}

static const u_char
unix2dos[256] = {
        0,    0,    0,    0,    0,    0,    0,    0,    /* 00-07 */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 08-0f */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 10-17 */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 18-1f */
        0,    0x21, 0,    0x23, 0x24, 0x25, 0x26, 0x27, /* 20-27 */
        0x28, 0x29, 0,    0,    0,    0x2d, 0,    0,    /* 28-2f */
        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* 30-37 */
        0x38, 0x39, 0,    0,    0,    0,    0,    0,    /* 38-3f */
        0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* 40-47 */
        0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, /* 48-4f */
        0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, /* 50-57 */
        0x58, 0x59, 0x5a, 0,    0,    0,    0x5e, 0x5f, /* 58-5f */
        0x60, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* 60-67 */
        0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, /* 68-6f */
        0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, /* 70-77 */
        0x58, 0x59, 0x5a, 0x7b, 0,    0x7d, 0x7e, 0,    /* 78-7f */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 80-87 */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 88-8f */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 90-97 */
        0,    0,    0,    0,    0,    0,    0,    0,    /* 98-9f */
        0,    0xad, 0xbd, 0x9c, 0xcf, 0xbe, 0xdd, 0xf5, /* a0-a7 */
        0xf9, 0xb8, 0xa6, 0xae, 0xaa, 0xf0, 0xa9, 0xee, /* a8-af */
        0xf8, 0xf1, 0xfd, 0xfc, 0xef, 0xe6, 0xf4, 0xfa, /* b0-b7 */
        0xf7, 0xfb, 0xa7, 0xaf, 0xac, 0xab, 0xf3, 0xa8, /* b8-bf */
        0xb7, 0xb5, 0xb6, 0xc7, 0x8e, 0x8f, 0x92, 0x80, /* c0-c7 */
        0xd4, 0x90, 0xd2, 0xd3, 0xde, 0xd6, 0xd7, 0xd8, /* c8-cf */
        0xd1, 0xa5, 0xe3, 0xe0, 0xe2, 0xe5, 0x99, 0x9e, /* d0-d7 */
        0x9d, 0xeb, 0xe9, 0xea, 0x9a, 0xed, 0xe8, 0xe1, /* d8-df */
        0xb7, 0xb5, 0xb6, 0xc7, 0x8e, 0x8f, 0x92, 0x80, /* e0-e7 */
        0xd4, 0x90, 0xd2, 0xd3, 0xde, 0xd6, 0xd7, 0xd8, /* e8-ef */
        0xd1, 0xa5, 0xe3, 0xe0, 0xe2, 0xe5, 0x99, 0xf6, /* f0-f7 */
        0x9d, 0xeb, 0xe9, 0xea, 0x9a, 0xed, 0xe8, 0x98, /* f8-ff */
};

static const u_char
u2l[256] = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 00-07 */
        0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* 08-0f */
        0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, /* 10-17 */
        0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, /* 18-1f */
        0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, /* 20-27 */
        0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, /* 28-2f */
        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* 30-37 */
        0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, /* 38-3f */
        0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 40-47 */
        0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, /* 48-4f */
        0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, /* 50-57 */
        0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, /* 58-5f */
        0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 60-67 */
        0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, /* 68-6f */
        0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, /* 70-77 */
        0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, /* 78-7f */
        0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, /* 80-87 */
        0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, /* 88-8f */
        0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, /* 90-97 */
        0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, /* 98-9f */
        0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, /* a0-a7 */
        0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, /* a8-af */
        0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, /* b0-b7 */
        0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, /* b8-bf */
        0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, /* c0-c7 */
        0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, /* c8-cf */
        0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xd7, /* d0-d7 */
        0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xdf, /* d8-df */
        0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, /* e0-e7 */
        0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, /* e8-ef */
        0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, /* f0-f7 */
        0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff, /* f8-ff */
};

/*
 * DOS filenames are made of 2 parts, the name part and the extension part.
 * The name part is 8 characters long and the extension part is 3
 * characters long.  They may contain trailing blanks if the name or
 * extension are not long enough to fill their respective fields.
 */

/*
 * Convert a unix filename to a DOS filename according to Win95 rules.
 * If applicable and gen is not 0, it is inserted into the converted
 * filename as a generation number.
 * Returns
 *      0 if name couldn't be converted
 *      1 if the converted name is the same as the original
 *        (no long filename entry necessary for Win95)
 *      2 if conversion was successful
 *      3 if conversion was successful and generation number was inserted
 */
int
unix2dosfn(u_char *un, u_char dn[11], int unlen, u_int gen)
{
        int i, j, l;
        int conv = 1;
        u_char *cp, *dp, *dp1;
        u_char gentext[6];

        /*
         * Fill the dos filename string with blanks. These are DOS's pad
         * characters.
         */
        for (i = 0; i < 11; i++)
                dn[i] = ' ';

        /*
         * The filenames "." and ".." are handled specially, since they
         * don't follow dos filename rules.
         */
        if (un[0] == '.' && unlen == 1) {
                dn[0] = '.';
                return gen <= 1;
        }
        if (un[0] == '.' && un[1] == '.' && unlen == 2) {
                dn[0] = '.';
                dn[1] = '.';
                return gen <= 1;
        }

        /*
         * Filenames with only blanks and dots are not allowed!
         */
        for (cp = un, i = unlen; --i >= 0; cp++)
                if (*cp != ' ' && *cp != '.')
                        break;
        if (i < 0)
                return 0;

        /*
         * Now find the extension
         * Note: dot as first char doesn't start extension
         *       and trailing dots and blanks are ignored
         */
        dp = dp1 = 0;
        for (cp = un + 1, i = unlen - 1; --i >= 0;) {
                switch (*cp++) {
                case '.':
                        if (!dp1)
                                dp1 = cp;
                        break;
                case ' ':
                        break;
                default:
                        if (dp1)
                                dp = dp1;
                        dp1 = 0;
                        break;
                }
        }

        /*
         * Now convert it
         */
        if (dp) {
                if (dp1)
                        l = dp1 - dp;
                else
                        l = unlen - (dp - un);
                for (i = 0, j = 8; i < l && j < 11; i++, j++) {
                        if (dp[i] != (dn[j] = unix2dos[dp[i]])
                            && conv != 3)
                                conv = 2;
                        if (!dn[j]) {
                                conv = 3;
                                dn[j--] = ' ';
                        }
                }
                if (i < l)
                        conv = 3;
                dp--;
        } else {
                for (dp = cp; *--dp == ' ' || *dp == '.';);
                dp++;
        }

        /*
         * Now convert the rest of the name
         */
        for (i = j = 0; un < dp && j < 8; i++, j++, un++) {
                if (*un != (dn[j] = unix2dos[*un])
                    && conv != 3)
                        conv = 2;
                if (!dn[j]) {
                        conv = 3;
                        dn[j--] = ' ';
                }
        }
        if (un < dp)
                conv = 3;
        /*
         * If we didn't have any chars in filename,
         * generate a default
         */
        if (!j)
                dn[0] = '_';

        /*
         * The first character cannot be E5,
         * because that means a deleted entry
         */
        if (dn[0] == 0xe5)
                dn[0] = SLOT_E5;

        /*
         * If there wasn't any char dropped,
         * there is no place for generation numbers
         */
        if (conv != 3) {
                if (gen > 1)
                        return 0;
                return conv;
        }

        /*
         * Now insert the generation number into the filename part
         */
        for (cp = gentext + sizeof(gentext); cp > gentext && gen; gen /= 10)
                *--cp = gen % 10 + '0';
        if (gen)
                return 0;
        for (i = 8; dn[--i] == ' ';);
        if (gentext + sizeof(gentext) - cp + 1 > 8 - i)
                i = 8 - (gentext + sizeof(gentext) - cp + 1);
        dn[i++] = '~';
        while (cp < gentext + sizeof(gentext))
                dn[i++] = *cp++;
        return 3;
}

/*
 * Create a Win95 long name directory entry
 * Note: assumes that the filename is valid,
 *       i.e. doesn't consist solely of blanks and dots
 */
int
unix2winfn(u_char *un, int unlen, struct winentry *wep, int cnt, int chksum)
{
        u_int8_t *cp;
        int i;

        /*
         * Drop trailing blanks and dots
         */
        for (cp = un + unlen; *--cp == ' ' || *cp == '.'; unlen--);

        un += (cnt - 1) * WIN_CHARS;
        unlen -= (cnt - 1) * WIN_CHARS;

        /*
         * Initialize winentry to some useful default
         */
        for (cp = (u_int8_t *)wep, i = sizeof(*wep); --i >= 0; *cp++ = 0xff);
        wep->weCnt = cnt;
        wep->weAttributes = ATTR_WIN95;
        wep->weReserved1 = 0;
        wep->weChksum = chksum;
        wep->weReserved2 = 0;

        /*
         * Now convert the filename parts
         */
        for (cp = wep->wePart1, i = sizeof(wep->wePart1)/2; --i >= 0;) {
                if (--unlen < 0)
                        goto done;
                *cp++ = *un++;
                *cp++ = 0;
        }
        for (cp = wep->wePart2, i = sizeof(wep->wePart2)/2; --i >= 0;) {
                if (--unlen < 0)
                        goto done;
                *cp++ = *un++;
                *cp++ = 0;
        }
        for (cp = wep->wePart3, i = sizeof(wep->wePart3)/2; --i >= 0;) {
                if (--unlen < 0)
                        goto done;
                *cp++ = *un++;
                *cp++ = 0;
        }
        if (!unlen)
                wep->weCnt |= WIN_LAST;
        return unlen;

done:
        *cp++ = 0;
        *cp++ = 0;
        wep->weCnt |= WIN_LAST;
        return 0;
}

/*
 * Compare our filename to the one in the Win95 entry
 * Returns the checksum or -1 if no match
 */
int
winChkName(u_char *un, int unlen, struct winentry *wep, int chksum)
{
        u_int8_t *cp;
        int i;

        /*
         * First compare checksums
         */
        if (wep->weCnt&WIN_LAST)
                chksum = wep->weChksum;
        else if (chksum != wep->weChksum)
                chksum = -1;
        if (chksum == -1)
                return -1;

        /*
         * Offset of this entry
         */
        i = ((wep->weCnt&WIN_CNT) - 1) * WIN_CHARS;
        if ((unlen -= i) <= 0)
                return -1;
        un += i;

        if ((wep->weCnt&WIN_LAST) && unlen > WIN_CHARS)
                return -1;

        /*
         * Compare the name parts
         */
        for (cp = wep->wePart1, i = sizeof(wep->wePart1)/2; --i >= 0;) {
                if (--unlen < 0) {
                        if (!*cp++ && !*cp)
                                return chksum;
                        return -1;
                }
                if (u2l[*cp++] != u2l[*un++] || *cp++)
                        return -1;
        }
        for (cp = wep->wePart2, i = sizeof(wep->wePart2)/2; --i >= 0;) {
                if (--unlen < 0) {
                        if (!*cp++ && !*cp)
                                return chksum;
                        return -1;
                }
                if (u2l[*cp++] != u2l[*un++] || *cp++)
                        return -1;
        }
        for (cp = wep->wePart3, i = sizeof(wep->wePart3)/2; --i >= 0;) {
                if (--unlen < 0) {
                        if (!*cp++ && !*cp)
                                return chksum;
                        return -1;
                }
                if (u2l[*cp++] != u2l[*un++] || *cp++)
                        return -1;
        }
        return chksum;
}

/*
 * Compute the checksum of a DOS filename for Win95 use
 */
u_int8_t
winChksum(u_int8_t *name)
{
        int i;
        u_int8_t s;

        for (s = 0, i = 11; --i >= 0; s += *name++)
                s = (s << 7)|(s >> 1);
        return s;
}

/*
 * Determine the number of slots necessary for Win95 names
 */
int
winSlotCnt(u_char *un, int unlen)
{
        for (un += unlen; unlen > 0; unlen--)
                if (*--un != ' ' && *un != '.')
                        break;
        if (unlen > WIN_MAXLEN)
                return 0;
        return howmany(unlen, WIN_CHARS);
}