/*      $NetBSD: msdosfs_conv.c,v 1.20 2023/06/02 08:51:47 andvar 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
 *
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#ifndef _KERNEL
#include <assert.h>
#define KASSERT(x)     assert(x)
#endif

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: msdosfs_conv.c,v 1.20 2023/06/02 08:51:47 andvar Exp $");

/*
 * System include files.
 */
#include <sys/param.h>
#include <sys/time.h>
#include <sys/endian.h>
#ifdef _KERNEL
#include <sys/dirent.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#else
#include <stdio.h>
#include <string.h>
#include <dirent.h>
#include <sys/queue.h>
#endif
#include <dev/clock_subr.h>

/*
 * MSDOSFS include files.
 */
#include <fs/msdosfs/direntry.h>
#include <fs/msdosfs/denode.h>

static int invalidname(const u_int16_t *, int);

static int ucs2utf8(const u_int16_t *, u_int8_t *, int);
static int utf8ucs2(const u_int8_t *, int, u_int16_t *);

static int ucs2utf8str(const u_int16_t *, int, u_int8_t *, int);
static int utf8ucs2str(const u_int8_t *, int, u_int16_t *, int);
static int ucs2char8str(const u_int16_t *, int, u_int8_t *, int);
static int char8ucs2str(const u_int8_t *, int, u_int16_t *, int);

static void ucs2pad(u_int16_t *, int, int);

static u_int16_t ucs2fold(u_int16_t);
static int ucs2match(u_int16_t *, u_int16_t *, int n);
static int char8match(u_int16_t *, u_int16_t *, int n);

/*
 * The number of seconds between Jan 1, 1970 and Jan 1, 1980. In that
 * interval there were 8 regular years and 2 leap years.
 */
#define DOSBIASYEAR     1980
#define SECONDSTO1980   (((8 * 365) + (2 * 366)) * (24 * 60 * 60))
/*
 * msdos fs can not store dates beyond the year 2234
 */
#define DOSMAXYEAR      ((DD_YEAR_MASK >> DD_YEAR_SHIFT) + DOSBIASYEAR)

/*
 * 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
msdosfs_unix2dostime(const struct timespec *tsp, int gmtoff,
    u_int16_t *ddp, u_int16_t *dtp, u_int8_t *dhp)
{
        u_long t;
        struct clock_ymdhms ymd;

        t = tsp->tv_sec + gmtoff; /* time zone correction */

        /*
         * DOS timestamps can not represent dates before 1980.
         */
        if (t < SECONDSTO1980)
                goto invalid_dos_date;

        /*
         * DOS granularity is 2 seconds
         */
        t &= ~1;

        /*
         * Convert to year/month/day/.. format
         */
        clock_secs_to_ymdhms(t, &ymd);
        if (ymd.dt_year > DOSMAXYEAR)
                goto invalid_dos_date;

        /*
         * Now transform to DOS format
         */
        *ddp = (ymd.dt_day << DD_DAY_SHIFT)
            + (ymd.dt_mon << DD_MONTH_SHIFT)
            + ((ymd.dt_year - DOSBIASYEAR) << DD_YEAR_SHIFT);
        if (dhp)
                *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000;
        if (dtp)
                *dtp = (((t / 2) % 30) << DT_2SECONDS_SHIFT)
                    + (((t / 60) % 60) << DT_MINUTES_SHIFT)
                    + (((t / 3600) % 24) << DT_HOURS_SHIFT);
        return;

invalid_dos_date:
        *ddp = 0;
        if (dtp)
                *dtp = 0;
        if (dhp)
                *dhp = 0;
}

/*
 * Convert from dos' idea of time to unix'. This will probably only be
 * called from the stat(), and fstat() system calls and so probably need
 * not be too efficient.
 */
void
msdosfs_dos2unixtime(u_int dd, u_int dt, u_int dh, int gmtoff,
    struct timespec *tsp)
{
        time_t seconds;
        struct clock_ymdhms ymd;

        if (dd == 0) {
                /*
                 * Uninitialized field, return the epoch.
                 */
                tsp->tv_sec = 0;
                tsp->tv_nsec = 0;
                return;
        }

        memset(&ymd, 0, sizeof(ymd));
        ymd.dt_year = ((dd & DD_YEAR_MASK) >> DD_YEAR_SHIFT) + 1980 ;
        ymd.dt_mon = ((dd & DD_MONTH_MASK) >> DD_MONTH_SHIFT);
        ymd.dt_day = ((dd & DD_DAY_MASK) >> DD_DAY_SHIFT);
        ymd.dt_hour = (dt & DT_HOURS_MASK) >> DT_HOURS_SHIFT;
        ymd.dt_min = (dt & DT_MINUTES_MASK) >> DT_MINUTES_SHIFT;
        ymd.dt_sec = ((dt & DT_2SECONDS_MASK) >> DT_2SECONDS_SHIFT) * 2;

        seconds = clock_ymdhms_to_secs(&ymd);

        tsp->tv_sec = seconds;
        tsp->tv_sec -= gmtoff;  /* time zone correction */
        tsp->tv_nsec = (dh % 100) * 10000000;
}

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,    '!',  0,    '#',  '$',  '%',  '&',  '\'', /* 20-27 */
        '(',  ')',  0,    '+',  0,    '-',  0,    0,    /* 28-2f */
        '0',  '1',  '2',  '3',  '4',  '5',  '6',  '7',  /* 30-37 */
        '8',  '9',  0,    0,    0,    0,    0,    0,    /* 38-3f */
        '@',  'A',  'B',  'C',  'D',  'E',  'F',  'G',  /* 40-47 */
        'H',  'I',  'J',  'K',  'L',  'M',  'N',  'O',  /* 48-4f */
        'P',  'Q',  'R',  'S',  'T',  'U',  'V',  'W',  /* 50-57 */
        'X',  'Y',  'Z',  0,    0,    0,    '^',  '_',  /* 58-5f */
        '`',  'A',  'B',  'C',  'D',  'E',  'F',  'G',  /* 60-67 */
        'H',  'I',  'J',  'K',  'L',  'M',  'N',  'O',  /* 68-6f */
        'P',  'Q',  'R',  'S',  'T',  'U',  'V',  'W',  /* 70-77 */
        'X',  'Y',  'Z',  '{',  0,    '}',  '~',  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
dos2unix[256] = {
         '?',  '?',  '?',  '?',  '?',  '?',  '?',  '?', /* 00-07 */
         '?',  '?',  '?',  '?',  '?',  '?',  '?',  '?', /* 08-0f */
         '?',  '?',  '?',  '?',  '?',  '?',  '?',  '?', /* 10-17 */
         '?',  '?',  '?',  '?',  '?',  '?',  '?',  '?', /* 18-1f */
         ' ',  '!',  '"',  '#',  '$',  '%',  '&', '\'', /* 20-27 */
         '(',  ')',  '*',  '+',  ',',  '-',  '.',  '/', /* 28-2f */
         '0',  '1',  '2',  '3',  '4',  '5',  '6',  '7', /* 30-37 */
         '8',  '9',  ':',  ';',  '<',  '=',  '>',  '?', /* 38-3f */
         '@',  'A',  'B',  'C',  'D',  'E',  'F',  'G', /* 40-47 */
         'H',  'I',  'J',  'K',  'L',  'M',  'N',  'O', /* 48-4f */
         'P',  'Q',  'R',  'S',  'T',  'U',  'V',  'W', /* 50-57 */
         'X',  'Y',  'Z',  '[', '\\',  ']',  '^',  '_', /* 58-5f */
         '`',  'a',  'b',  'c',  'd',  'e',  'f',  'g', /* 60-67 */
         'h',  'i',  'j',  'k',  'l',  'm',  'n',  'o', /* 68-6f */
         'p',  'q',  'r',  's',  't',  'u',  'v',  'w', /* 70-77 */
         'x',  'y',  'z',  '{',  '|',  '}',  '~', 0x7f, /* 78-7f */
        0xc7, 0xfc, 0xe9, 0xe2, 0xe4, 0xe0, 0xe5, 0xe7, /* 80-87 */
        0xea, 0xeb, 0xe8, 0xef, 0xee, 0xec, 0xc4, 0xc5, /* 88-8f */
        0xc9, 0xe6, 0xc6, 0xf4, 0xf6, 0xf2, 0xfb, 0xf9, /* 90-97 */
        0xff, 0xd6, 0xdc, 0xf8, 0xa3, 0xd8, 0xd7,  '?', /* 98-9f */
        0xe1, 0xed, 0xf3, 0xfa, 0xf1, 0xd1, 0xaa, 0xba, /* a0-a7 */
        0xbf, 0xae, 0xac, 0xbd, 0xbc, 0xa1, 0xab, 0xbb, /* a8-af */
         '?',  '?',  '?',  '?',  '?', 0xc1, 0xc2, 0xc0, /* b0-b7 */
        0xa9,  '?',  '?',  '?',  '?', 0xa2, 0xa5,  '?', /* b8-bf */
         '?',  '?',  '?',  '?',  '?',  '?', 0xe3, 0xc3, /* c0-c7 */
         '?',  '?',  '?',  '?',  '?',  '?',  '?', 0xa4, /* c8-cf */
        0xf0, 0xd0, 0xca, 0xcb, 0xc8,  '?', 0xcd, 0xce, /* d0-d7 */
        0xcf,  '?',  '?',  '?',  '?', 0xa6, 0xcc,  '?', /* d8-df */
        0xd3, 0xdf, 0xd4, 0xd2, 0xf5, 0xd5, 0xb5, 0xfe, /* e0-e7 */
        0xde, 0xda, 0xdb, 0xd9, 0xfd, 0xdd, 0xaf, 0x3f, /* e8-ef */
        0xad, 0xb1,  '?', 0xbe, 0xb6, 0xa7, 0xf7, 0xb8, /* f0-f7 */
        0xb0, 0xa8, 0xb7, 0xb9, 0xb3, 0xb2,  '?',  '?', /* 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 */
         ' ',  '!',  '"',  '#',  '$',  '%',  '&', '\'', /* 20-27 */
         '(',  ')',  '*',  '+',  ',',  '-',  '.',  '/', /* 28-2f */
         '0',  '1',  '2',  '3',  '4',  '5',  '6',  '7', /* 30-37 */
         '8',  '9',  ':',  ';',  '<',  '=',  '>',  '?', /* 38-3f */
         '@',  'a',  'b',  'c',  'd',  'e',  'f',  'g', /* 40-47 */
         'h',  'i',  'j',  'k',  'l',  'm',  'n',  'o', /* 48-4f */
         'p',  'q',  'r',  's',  't',  'u',  'v',  'w', /* 50-57 */
         'x',  'y',  'z',  '[', '\\',  ']',  '^',  '_', /* 58-5f */
         '`',  'a',  'b',  'c',  'd',  'e',  'f',  'g', /* 60-67 */
         'h',  'i',  'j',  'k',  'l',  'm',  'n',  'o', /* 68-6f */
         'p',  'q',  'r',  's',  't',  'u',  'v',  'w', /* 70-77 */
         'x',  'y',  'z',  '{',  '|',  '}',  '~', 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 DOS filename to a unix filename. And, return the number of
 * characters in the resulting unix filename excluding the terminating
 * null.
 */
int
msdosfs_dos2unixfn(u_char dn[11], u_char *un, int lower)
{
        int i, j;
        int thislong = 1;
        u_char c;

        /*
         * If first char of the filename is SLOT_E5 (0x05), then the real
         * first char of the filename should be 0xe5. But, they couldn't
         * just have a 0xe5 mean 0xe5 because that is used to mean a freed
         * directory slot. Another dos quirk.
         */
        if (*dn == SLOT_E5)
                c = dos2unix[0xe5];
        else
                c = dos2unix[*dn];
        *un++ = lower ? u2l[c] : c;

        /*
         * Copy the rest into the unix filename string, ignoring
         * trailing blanks.
         */

        for (j=7; (j >= 0) && (dn[j] == ' '); j--)
                ;

        for (i = 1; i <= j; i++) {
                c = dos2unix[dn[i]];
                *un++ = lower ? u2l[c] : c;
                thislong++;
        }
        dn += 8;

        /*
         * Now, if there is an extension then put in a period and copy in
         * the extension.
         */
        if (*dn != ' ') {
                *un++ = '.';
                thislong++;
                for (i = 0; i < 3 && *dn != ' '; i++) {
                        c = dos2unix[*dn++];
                        *un++ = lower ? u2l[c] : c;
                        thislong++;
                }
        }
        *un++ = 0;

        return (thislong);
}

/*
 * 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
msdosfs_unix2dosfn(const u_char *un, u_char dn[12], int unlen, u_int gen)
{
        int i, j, l;
        int conv = 1;
        const u_char *cp, *dp, *dp1;
        u_char gentext[6], *wcp;
        int shortlen;

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

        /*
         * 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++;
        }

        shortlen = (dp - un) <= 8;

        /*
         * Now convert the rest of the name
         */
        for (i = j = 0; un < dp && j < 8; i++, j++, un++) {
                if ((*un == ' ') && shortlen)
                        dn[j] = ' ';
                else
                        dn[j] = unix2dos[*un];
                if ((*un != dn[j])
                    && 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 (wcp = gentext + sizeof(gentext); wcp > gentext && gen; gen /= 10)
                *--wcp = gen % 10 + '0';
        if (gen)
                return 0;
        for (i = 8; dn[--i] == ' ';);
        i++;
        if (gentext + sizeof(gentext) - wcp + 1 > 8 - i)
                i = 8 - (gentext + sizeof(gentext) - wcp + 1);
        dn[i++] = '~';
        while (wcp < gentext + sizeof(gentext))
                dn[i++] = *wcp++;
        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
msdosfs_unix2winfn(const u_char *un, int unlen, struct winentry *wep, int cnt,
    int chksum, int utf8)
{
        u_int16_t wn[WIN_MAXLEN], *p;
        int i, len;
        const u_char *cp;

        /*
         * Drop trailing blanks and dots
         */
        for (cp = un + unlen; unlen > 0; unlen--)
                if (*--cp != ' ' && *cp != '.')
                        break;

        /*
         * Offset of this entry
         */
        i = (cnt - 1) * WIN_CHARS;

        /*
         * Translate UNIX name to ucs-2
         */
        len = utf8 ? utf8ucs2str(un, unlen, wn, WIN_MAXLEN) : char8ucs2str(un, unlen, wn, WIN_MAXLEN);
        ucs2pad(wn, len, WIN_MAXLEN);

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

        /*
         * Store name segment into directory entry
         */
        p = &wn[i];
        memcpy(wep->wePart1, p, sizeof(wep->wePart1));
        p += sizeof(wep->wePart1) / sizeof(*p);
        memcpy(wep->wePart2, p, sizeof(wep->wePart2));
        p += sizeof(wep->wePart2) / sizeof(*p);
        memcpy(wep->wePart3, p, sizeof(wep->wePart3));
        
        if (len > i + WIN_CHARS)
                return 1;

        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
msdosfs_winChkName(const u_char *un, int unlen, struct winentry *wep,
    int chksum, int utf8)
{
        u_int16_t wn[WIN_MAXLEN], *p;
        u_int16_t buf[WIN_CHARS];
        int i, len;

        /*
         * 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;

        /*
         * Translate UNIX name to ucs-2
         */
        len = utf8 ? utf8ucs2str(un, unlen, wn, WIN_MAXLEN) : char8ucs2str(un, unlen, wn, WIN_MAXLEN);
        ucs2pad(wn, len, WIN_MAXLEN);

        if (i >= len + 1)
                return -1;
        if ((wep->weCnt & WIN_LAST) && (len - i > WIN_CHARS))
                return -1;

        /*
         * Fetch name segment from directory entry
         */
        p = &buf[0];
        memcpy(p, wep->wePart1, sizeof(wep->wePart1));
        p += sizeof(wep->wePart1) / sizeof(*p);
        memcpy(p, wep->wePart2, sizeof(wep->wePart2));
        p += sizeof(wep->wePart2) / sizeof(*p);
        memcpy(p, wep->wePart3, sizeof(wep->wePart3));

        /*
         * And compare name segment
         */
        if (! (utf8 ? ucs2match(&wn[i], buf, WIN_CHARS) : char8match(&wn[i], buf, WIN_CHARS)))
                return -1;

        return chksum;
}

/*
 * Convert Win95 filename to dirbuf.
 * Returns the checksum or -1 if impossible
 */
int
msdosfs_win2unixfn(struct winentry *wep, struct dirent *dp, int chksum,
    uint16_t *namlen, int utf8)
{
        u_int16_t wn[WIN_CHARS], *p;
        u_int8_t buf[WIN_CHARS*3];
        int len;

        if ((wep->weCnt & WIN_CNT) > howmany(WIN_MAXLEN, WIN_CHARS)
            || !(wep->weCnt & WIN_CNT))
                return -1;

        /*
         * First compare checksums
         */
        if (wep->weCnt & WIN_LAST) {
                chksum = wep->weChksum;
                *namlen = 0;
        } else if (chksum != wep->weChksum)
                chksum = -1;
        if (chksum == -1)
                return -1;

        /*
         * Fetch name segment from directory entry
         */
        p = &wn[0];
        memcpy(p, wep->wePart1, sizeof(wep->wePart1));
        p += sizeof(wep->wePart1) / sizeof(*p);
        memcpy(p, wep->wePart2, sizeof(wep->wePart2));
        p += sizeof(wep->wePart2) / sizeof(*p);
        memcpy(p, wep->wePart3, sizeof(wep->wePart3));

        /*
         * Don't allow slashes in UNIX names. Discard that entry.
         */
        if (invalidname(wn, WIN_CHARS))
                return -1;

        /*
         * Translate ucs-2 to UNIX name
         */
        len = utf8 ? ucs2utf8str(wn, WIN_CHARS, buf, sizeof(buf))
            : ucs2char8str(wn, WIN_CHARS, buf, sizeof(buf));

        KASSERT(len >= 0);
        KASSERT((size_t)len <= MIN(sizeof(buf), sizeof(dp->d_name)-1));

        /*
         * Prepend name segment to directory entry
         *
         * This ignores the slot number from the windows entry but
         * assumes that segments are read in reverse order.
         *
         * The UCS-2 name (up to 255 chars) can overflow the UNIX
         * directory entry (up to 511 bytes). Trailing characters
         * are silently discarded. This could also end in multiple
         * files using the same (truncated) name.
         */
        *namlen += len;
        if (*namlen > sizeof(dp->d_name) - 1)
                *namlen = sizeof(dp->d_name) - 1;

        KASSERT(*namlen >= len);

        memmove(&dp->d_name[len], &dp->d_name[0], *namlen - len);
        memcpy(dp->d_name, buf, len);

        return chksum;
}

/*
 * Compute the checksum of a DOS filename for Win95 use
 */
u_int8_t
msdosfs_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
msdosfs_winSlotCnt(const u_char *un, int unlen, int utf8)
{
        const u_char *cp;
        int len;

        /*
         * Drop trailing blanks and dots
         */
        for (cp = un + unlen; unlen > 0; unlen--)
                if (*--cp != ' ' && *cp != '.')
                        break;

        len = utf8 ? utf8ucs2str(un, unlen, NULL, WIN_MAXLEN) : unlen;

        return howmany(len, WIN_CHARS);
}

/*
 * Scan windows name for characters that must not
 * appear in a UNIX filename
 */
static int
invalidname(const u_int16_t *in, int n)
{
        while (n-- > 0) {
                if (*in++ == '/')
                        return 1;
        }

        return 0;
}

/*
 * Convert UCS-2 character into UTF-8
 * return number of output bytes or 0 if output
 * buffer is too short
 */
static int
ucs2utf8(const u_int16_t *in, u_int8_t *out, int n)
{
        uint16_t inch = le16toh(in[0]);

        if (inch <= 0x007f) {
                if (n < 1) return 0;
                if (out)
                        *out++ = inch;
                return 1;
        } else if (inch <= 0x07ff) {
                if (n < 2) return 0;
                if (out) {
                        *out++ = 0xc0 | (inch >> 6);
                        *out++ = 0x80 | (inch & 0x3f);
                }
                return 2;
        } else {
                if (n < 3) return 0;
                if (out) {
                        *out++ = 0xe0 | (inch >> 12);
                        *out++ = 0x80 | ((inch >> 6) & 0x3f);
                        *out++ = 0x80 | (inch & 0x3f);
                }
                return 3;
        }
}


/*
 * Convert UTF-8 bytes into UCS-2 character
 * return number of input bytes, 0 if input
 * is too short and -1 if input is invalid
 */
static int
utf8ucs2(const u_int8_t *in, int n, u_int16_t *out)
{
        uint16_t outch;

        if (n < 1) return 0;

        if (in[0] <= 0x7f) {
                outch = in[0];
                if (out)
                        *out = htole16(outch);
                return 1;
        } else if (in[0] <= 0xdf) {
                if (n < 2) return 0;
                outch = (in[0] & 0x1f) << 6 | (in[1] & 0x3f);
                if (out)
                        *out = htole16(outch);
                return 2;
        } else if (in[0] <= 0xef) {
                if (n < 3) return 0;
                outch = (in[0] & 0x1f) << 12 | (in[1] & 0x3f) << 6 | (in[2] & 0x3f);
                if (out)
                        *out = htole16(outch);
                return 3;
        }

        return -1;
}

/*
 * Convert UCS-2 string into UTF-8 string
 * return total number of output bytes
 */
static int
ucs2utf8str(const u_int16_t *in, int n, u_int8_t *out, int m)
{
        u_int8_t *p;
        int outlen;

        p = out;
        while (n > 0 && *in != 0) {
                outlen = ucs2utf8(in, out ? p : out, m);
                if (outlen == 0)
                        break;
                p += outlen;
                m -= outlen;
                in += 1;
                n -= 1;
        }

        return p - out;
}

/*
 * Convert UTF8 string into UCS-2 string
 * return total number of output characters
 */
static int
utf8ucs2str(const u_int8_t *in, int n, u_int16_t *out, int m)
{
        u_int16_t *p;
        int inlen;

        p = out;
        while (n > 0 && *in != 0) {
                if (m < 1)
                        break;
                inlen = utf8ucs2(in, n, out ? p : out);
                if (inlen <= 0)
                        break;
                in += inlen;
                n -= inlen;
                p += 1;
                m -= 1;
        }

        return p - out;
}

/*
 * Convert UCS-2 string into 8bit character string
 * return total number of output bytes
 */
static int
ucs2char8str(const u_int16_t *in, int n, u_int8_t *out, int m)
{
        u_int8_t *p;
        u_int16_t inch;

        p = out;
        while (n > 0 && in[0] != 0) {
                if (m < 1)
                        break;
                inch = le16toh(in[0]);
                if (inch > 255)
                        break;
                if (p)
                        p[0] = inch;
                p += 1;
                m -= 1;
                in += 1;
                n -= 1;
        }

        return p - out;
}

/*
 * Convert 8bit character string into UCS-2 string
 * return total number of output characters
 */
static int
char8ucs2str(const u_int8_t *in, int n, u_int16_t *out, int m)
{
        u_int16_t *p;

        p = out;
        while (n > 0 && in[0] != 0) {
                if (m < 1)
                        break;
                if (p)
                        p[0] = htole16(in[0]);
                p += 1;
                m -= 1;
                in += 1;
                n -= 1;
        }

        return p - out;
}

static void
ucs2pad(u_int16_t *buf, int len, int size)
{

        if (len < size-1)
                buf[len++] = 0x0000;
        while (len < size)
                buf[len++] = 0xffff;
}

/*
 * Fold UCS-2 character to uppercase
 */
static u_int16_t
ucs2fold(u_int16_t w)
{
        int low,high,mid;
        u_int16_t check;
        extern const u_int16_t msdosfs_unicode_foldmap[];
        extern size_t msdosfs_unicode_foldmap_entries;

        w = le16toh(w);

        low = 0;
        high = msdosfs_unicode_foldmap_entries / 2;
        while (low < high) {
                mid = (low + high)/2;
                check = msdosfs_unicode_foldmap[2*mid+0];

                if (w == check) {
                        w = msdosfs_unicode_foldmap[2*mid+1];
                        break;
                }

                if (w < check)
                        high = mid;
                else
                        low = mid+1;
        }

        w = le16toh(w);

        return w;
}

/*
 * Compare two UCS-2 strings case-insensitive
 *
 * uses the Unicode case folding table
 */
static int
ucs2match(u_int16_t *w1, u_int16_t *w2, int n)
{
        u_int16_t u1, u2;

        while (n > 0) {
                if (*w1 == 0 || *w2 == 0)
                        return *w1 == *w2;
                u1 = ucs2fold(*w1);
                u2 = ucs2fold(*w2);
                if (u1 != u2)
                        return 0;
                ++w1;
                ++w2;
                --n;
        }

        return 1;
}

/*
 * Compare two 8bit char conversions case-insensitive
 *
 * uses the DOS case folding table
 */
static int
char8match(u_int16_t *w1, u_int16_t *w2, int n)
{
        u_int16_t u1, u2;

        while (n > 0) {
                u1 = le16toh(*w1);
                u2 = le16toh(*w2);
                if (u1 == 0 || u2 == 0)
                        return u1 == u2;
                if (u1 > 255 || u2 > 255)
                        return 0;
                u1 = u2l[u1 & 0xff];
                u2 = u2l[u2 & 0xff];
                if (u1 != u2)
                        return 0;
                ++w1;
                ++w2;
                --n;
        }

        return 1;
}