/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright 2022 MNX Cloud, Inc.
 */


/*
 * UTF-8 text preparation functions (PSARC/2007/149, PSARC/2007/458).
 *
 * Man pages: u8_textprep_open(9F), u8_textprep_buf(9F), u8_textprep_close(9F),
 * u8_textprep_str(9F), u8_strcmp(9F), and u8_validate(9F). See also
 * the section 3C man pages.
 * Interface stability: Committed.
 */

#include <sys/types.h>
#ifdef  _KERNEL
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/systm.h>
#include <sys/debug.h>
#include <sys/kmem.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#else
#include <sys/u8_textprep.h>
#include <strings.h>
#endif  /* _KERNEL */
#include <sys/byteorder.h>
#include <sys/errno.h>
#include <sys/u8_textprep_data.h>
#include <sys/sysmacros.h>


/* The maximum possible number of bytes in a UTF-8 character. */
#define U8_MB_CUR_MAX                   (4)

/*
 * The maximum number of bytes needed for a UTF-8 character to cover
 * U+0000 - U+FFFF, i.e., the coding space of now deprecated UCS-2.
 */
#define U8_MAX_BYTES_UCS2               (3)

/* The maximum possible number of bytes in a Stream-Safe Text. */
#define U8_STREAM_SAFE_TEXT_MAX         (128)

/*
 * The maximum number of characters in a combining/conjoining sequence and
 * the actual upperbound limit of a combining/conjoining sequence.
 */
#define U8_MAX_CHARS_A_SEQ              (32)
#define U8_UPPER_LIMIT_IN_A_SEQ         (31)

/* The combining class value for Starter. */
#define U8_COMBINING_CLASS_STARTER      (0)

/*
 * Some Hangul related macros at below.
 *
 * The first and the last of Hangul syllables, Hangul Jamo Leading consonants,
 * Vowels, and optional Trailing consonants in Unicode scalar values.
 *
 * Please be noted that the U8_HANGUL_JAMO_T_FIRST is 0x11A7 at below not
 * the actual U+11A8. This is due to that the trailing consonant is optional
 * and thus we are doing a pre-calculation of subtracting one.
 *
 * Each of 19 modern leading consonants has total 588 possible syllables since
 * Hangul has 21 modern vowels and 27 modern trailing consonants plus 1 for
 * no trailing consonant case, i.e., 21 x 28 = 588.
 *
 * We also have bunch of Hangul related macros at below. Please bear in mind
 * that the U8_HANGUL_JAMO_1ST_BYTE can be used to check whether it is
 * a Hangul Jamo or not but the value does not guarantee that it is a Hangul
 * Jamo; it just guarantee that it will be most likely.
 */
#define U8_HANGUL_SYL_FIRST             (0xAC00U)
#define U8_HANGUL_SYL_LAST              (0xD7A3U)

#define U8_HANGUL_JAMO_L_FIRST          (0x1100U)
#define U8_HANGUL_JAMO_L_LAST           (0x1112U)
#define U8_HANGUL_JAMO_V_FIRST          (0x1161U)
#define U8_HANGUL_JAMO_V_LAST           (0x1175U)
#define U8_HANGUL_JAMO_T_FIRST          (0x11A7U)
#define U8_HANGUL_JAMO_T_LAST           (0x11C2U)

#define U8_HANGUL_V_COUNT               (21)
#define U8_HANGUL_VT_COUNT              (588)
#define U8_HANGUL_T_COUNT               (28)

#define U8_HANGUL_JAMO_1ST_BYTE         (0xE1U)

#define U8_SAVE_HANGUL_AS_UTF8(s, i, j, k, b) \
        (s)[(i)] = (uchar_t)(0xE0U | ((uint32_t)(b) & 0xF000U) >> 12); \
        (s)[(j)] = (uchar_t)(0x80U | ((uint32_t)(b) & 0x0FC0U) >> 6); \
        (s)[(k)] = (uchar_t)(0x80U | ((uint32_t)(b) & 0x003FU));

#define U8_HANGUL_JAMO_L(u) \
        ((u) >= U8_HANGUL_JAMO_L_FIRST && (u) <= U8_HANGUL_JAMO_L_LAST)

#define U8_HANGUL_JAMO_V(u) \
        ((u) >= U8_HANGUL_JAMO_V_FIRST && (u) <= U8_HANGUL_JAMO_V_LAST)

#define U8_HANGUL_JAMO_T(u) \
        ((u) > U8_HANGUL_JAMO_T_FIRST && (u) <= U8_HANGUL_JAMO_T_LAST)

#define U8_HANGUL_JAMO(u) \
        ((u) >= U8_HANGUL_JAMO_L_FIRST && (u) <= U8_HANGUL_JAMO_T_LAST)

#define U8_HANGUL_SYLLABLE(u) \
        ((u) >= U8_HANGUL_SYL_FIRST && (u) <= U8_HANGUL_SYL_LAST)

#define U8_HANGUL_COMPOSABLE_L_V(s, u) \
        ((s) == U8_STATE_HANGUL_L && U8_HANGUL_JAMO_V((u)))

#define U8_HANGUL_COMPOSABLE_LV_T(s, u) \
        ((s) == U8_STATE_HANGUL_LV && U8_HANGUL_JAMO_T((u)))

/* The types of decomposition mappings. */
#define U8_DECOMP_BOTH                  (0xF5U)
#define U8_DECOMP_CANONICAL             (0xF6U)

/* The indicator for 16-bit table. */
#define U8_16BIT_TABLE_INDICATOR        (0x8000U)

/* The following are some convenience macros. */
#define U8_PUT_3BYTES_INTO_UTF32(u, b1, b2, b3) \
        (u) = ((uint32_t)(b1) & 0x0F) << 12 | ((uint32_t)(b2) & 0x3F) << 6 | \
                (uint32_t)(b3) & 0x3F;

#define U8_SIMPLE_SWAP(a, b, t) \
        (t) = (a); \
        (a) = (b); \
        (b) = (t);

#define U8_ASCII_TOUPPER(c) \
        (((c) >= 'a' && (c) <= 'z') ? (c) - 'a' + 'A' : (c))

#define U8_ASCII_TOLOWER(c) \
        (((c) >= 'A' && (c) <= 'Z') ? (c) - 'A' + 'a' : (c))

#define U8_ISASCII(c)                   (((uchar_t)(c)) < 0x80U)
/*
 * The following macro assumes that the two characters that are to be
 * swapped are adjacent to each other and 'a' comes before 'b'.
 *
 * If the assumptions are not met, then, the macro will fail.
 */
#define U8_SWAP_COMB_MARKS(a, b) \
        for (k = 0; k < disp[(a)]; k++) \
                u8t[k] = u8s[start[(a)] + k]; \
        for (k = 0; k < disp[(b)]; k++) \
                u8s[start[(a)] + k] = u8s[start[(b)] + k]; \
        start[(b)] = start[(a)] + disp[(b)]; \
        for (k = 0; k < disp[(a)]; k++) \
                u8s[start[(b)] + k] = u8t[k]; \
        U8_SIMPLE_SWAP(comb_class[(a)], comb_class[(b)], tc); \
        U8_SIMPLE_SWAP(disp[(a)], disp[(b)], tc);

/* The possible states during normalization. */
typedef enum {
        U8_STATE_START = 0,
        U8_STATE_HANGUL_L = 1,
        U8_STATE_HANGUL_LV = 2,
        U8_STATE_HANGUL_LVT = 3,
        U8_STATE_HANGUL_V = 4,
        U8_STATE_HANGUL_T = 5,
        U8_STATE_COMBINING_MARK = 6
} u8_normalization_states_t;

/*
 * The three vectors at below are used to check bytes of a given UTF-8
 * character are valid and not containing any malformed byte values.
 *
 * We used to have a quite relaxed UTF-8 binary representation but then there
 * was some security related issues and so the Unicode Consortium defined
 * and announced the UTF-8 Corrigendum at Unicode 3.1 and then refined it
 * one more time at the Unicode 3.2. The following three tables are based on
 * that.
 */

#define U8_ILLEGAL_NEXT_BYTE_COMMON(c)  ((c) < 0x80 || (c) > 0xBF)

#define I_                              U8_ILLEGAL_CHAR
#define O_                              U8_OUT_OF_RANGE_CHAR

const int8_t u8_number_of_bytes[0x100] = {
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
        1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,

/*      80  81  82  83  84  85  86  87  88  89  8A  8B  8C  8D  8E  8F  */
        I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_,

/*      90  91  92  93  94  95  96  97  98  99  9A  9B  9C  9D  9E  9F  */
        I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_,

/*      A0  A1  A2  A3  A4  A5  A6  A7  A8  A9  AA  AB  AC  AD  AE  AF  */
        I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_,

/*      B0  B1  B2  B3  B4  B5  B6  B7  B8  B9  BA  BB  BC  BD  BE  BF  */
        I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_, I_,

/*      C0  C1  C2  C3  C4  C5  C6  C7  C8  C9  CA  CB  CC  CD  CE  CF  */
        I_, I_, 2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,

/*      D0  D1  D2  D3  D4  D5  D6  D7  D8  D9  DA  DB  DC  DD  DE  DF  */
        2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,

/*      E0  E1  E2  E3  E4  E5  E6  E7  E8  E9  EA  EB  EC  ED  EE  EF  */
        3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  3,

/*      F0  F1  F2  F3  F4  F5  F6  F7  F8  F9  FA  FB  FC  FD  FE  FF  */
        4,  4,  4,  4,  4,  O_, O_, O_, O_, O_, O_, O_, O_, O_, O_, O_,
};

#undef  I_
#undef  O_

const uint8_t u8_valid_min_2nd_byte[0x100] = {
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
/*      C0    C1    C2    C3    C4    C5    C6    C7    */
        0,    0,    0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      C8    C9    CA    CB    CC    CD    CE    CF    */
        0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      D0    D1    D2    D3    D4    D5    D6    D7    */
        0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      D8    D9    DA    DB    DC    DD    DE    DF    */
        0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      E0    E1    E2    E3    E4    E5    E6    E7    */
        0xa0, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      E8    E9    EA    EB    EC    ED    EE    EF    */
        0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
/*      F0    F1    F2    F3    F4    F5    F6    F7    */
        0x90, 0x80, 0x80, 0x80, 0x80, 0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
};

const uint8_t u8_valid_max_2nd_byte[0x100] = {
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
/*      C0    C1    C2    C3    C4    C5    C6    C7    */
        0,    0,    0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf,
/*      C8    C9    CA    CB    CC    CD    CE    CF    */
        0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf,
/*      D0    D1    D2    D3    D4    D5    D6    D7    */
        0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf,
/*      D8    D9    DA    DB    DC    DD    DE    DF    */
        0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf,
/*      E0    E1    E2    E3    E4    E5    E6    E7    */
        0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0xbf,
/*      E8    E9    EA    EB    EC    ED    EE    EF    */
        0xbf, 0xbf, 0xbf, 0xbf, 0xbf, 0x9f, 0xbf, 0xbf,
/*      F0    F1    F2    F3    F4    F5    F6    F7    */
        0xbf, 0xbf, 0xbf, 0xbf, 0x8f, 0,    0,    0,
        0,    0,    0,    0,    0,    0,    0,    0,
};


/*
 * The u8_validate() validates on the given UTF-8 character string and
 * calculate the byte length. It is quite similar to mblen(3C) except that
 * this will validate against the list of characters if required and
 * specific to UTF-8 and Unicode.
 */
int
u8_validate(char *u8str, size_t n, char **list, int flag, int *errnum)
{
        uchar_t *ib;
        uchar_t *ibtail;
        uchar_t **p;
        uchar_t *s1;
        uchar_t *s2;
        uchar_t f;
        int sz;
        size_t i;
        int ret_val;
        boolean_t second;
        boolean_t no_need_to_validate_entire;
        boolean_t check_additional;
        boolean_t validate_ucs2_range_only;

        if (! u8str)
                return (0);

        ib = (uchar_t *)u8str;
        ibtail = ib + n;

        ret_val = 0;

        no_need_to_validate_entire = ! (flag & U8_VALIDATE_ENTIRE);
        check_additional = flag & U8_VALIDATE_CHECK_ADDITIONAL;
        validate_ucs2_range_only = flag & U8_VALIDATE_UCS2_RANGE;

        while (ib < ibtail) {
                /*
                 * The first byte of a UTF-8 character tells how many
                 * bytes will follow for the character. If the first byte
                 * is an illegal byte value or out of range value, we just
                 * return -1 with an appropriate error number.
                 */
                sz = u8_number_of_bytes[*ib];
                if (sz == U8_ILLEGAL_CHAR) {
                        *errnum = EILSEQ;
                        return (-1);
                }

                if (sz == U8_OUT_OF_RANGE_CHAR ||
                    (validate_ucs2_range_only && sz > U8_MAX_BYTES_UCS2)) {
                        *errnum = ERANGE;
                        return (-1);
                }

                /*
                 * If we don't have enough bytes to check on, that's also
                 * an error. As you can see, we give illegal byte sequence
                 * checking higher priority then EINVAL cases.
                 */
                if ((ibtail - ib) < sz) {
                        *errnum = EINVAL;
                        return (-1);
                }

                if (sz == 1) {
                        ib++;
                        ret_val++;
                } else {
                        /*
                         * Check on the multi-byte UTF-8 character. For more
                         * details on this, see comment added for the used
                         * data structures at the beginning of the file.
                         */
                        f = *ib++;
                        ret_val++;
                        second = B_TRUE;
                        for (i = 1; i < sz; i++) {
                                if (second) {
                                        if (*ib < u8_valid_min_2nd_byte[f] ||
                                            *ib > u8_valid_max_2nd_byte[f]) {
                                                *errnum = EILSEQ;
                                                return (-1);
                                        }
                                        second = B_FALSE;
                                } else if (U8_ILLEGAL_NEXT_BYTE_COMMON(*ib)) {
                                        *errnum = EILSEQ;
                                        return (-1);
                                }
                                ib++;
                                ret_val++;
                        }
                }

                if (check_additional) {
                        for (p = (uchar_t **)list, i = 0; p[i]; i++) {
                                s1 = ib - sz;
                                s2 = p[i];
                                while (s1 < ib) {
                                        if (*s1 != *s2 || *s2 == '\0')
                                                break;
                                        s1++;
                                        s2++;
                                }

                                if (s1 >= ib && *s2 == '\0') {
                                        *errnum = EBADF;
                                        return (-1);
                                }
                        }
                }

                if (no_need_to_validate_entire)
                        break;
        }

        return (ret_val);
}

/*
 * The do_case_conv() looks at the mapping tables and returns found
 * bytes if any. If not found, the input bytes are returned. The function
 * always terminate the return bytes with a null character assuming that
 * there are plenty of room to do so.
 *
 * The case conversions are simple case conversions mapping a character to
 * another character as specified in the Unicode data. The byte size of
 * the mapped character could be different from that of the input character.
 *
 * The return value is the byte length of the returned character excluding
 * the terminating null byte.
 */
static size_t
do_case_conv(int uv, uchar_t *u8s, uchar_t *s, int sz, boolean_t is_it_toupper)
{
        size_t i;
        uint16_t b1 = 0;
        uint16_t b2 = 0;
        uint16_t b3 = 0;
        uint16_t b3_tbl;
        uint16_t b3_base;
        uint16_t b4 = 0;
        size_t start_id;
        size_t end_id;

        /*
         * At this point, the only possible values for sz are 2, 3, and 4.
         * The u8s should point to a vector that is well beyond the size of
         * 5 bytes.
         */
        if (sz == 2) {
                b3 = u8s[0] = s[0];
                b4 = u8s[1] = s[1];
        } else if (sz == 3) {
                b2 = u8s[0] = s[0];
                b3 = u8s[1] = s[1];
                b4 = u8s[2] = s[2];
        } else if (sz == 4) {
                b1 = u8s[0] = s[0];
                b2 = u8s[1] = s[1];
                b3 = u8s[2] = s[2];
                b4 = u8s[3] = s[3];
        } else {
                /* This is not possible but just in case as a fallback. */
                if (is_it_toupper)
                        *u8s = U8_ASCII_TOUPPER(*s);
                else
                        *u8s = U8_ASCII_TOLOWER(*s);
                u8s[1] = '\0';

                return (1);
        }
        u8s[sz] = '\0';

        /*
         * Let's find out if we have a corresponding character.
         */
        b1 = u8_common_b1_tbl[uv][b1];
        if (b1 == U8_TBL_ELEMENT_NOT_DEF)
                return ((size_t)sz);

        b2 = u8_case_common_b2_tbl[uv][b1][b2];
        if (b2 == U8_TBL_ELEMENT_NOT_DEF)
                return ((size_t)sz);

        if (is_it_toupper) {
                b3_tbl = u8_toupper_b3_tbl[uv][b2][b3].tbl_id;
                if (b3_tbl == U8_TBL_ELEMENT_NOT_DEF)
                        return ((size_t)sz);

                start_id = u8_toupper_b4_tbl[uv][b3_tbl][b4];
                end_id = u8_toupper_b4_tbl[uv][b3_tbl][b4 + 1];

                /* Either there is no match or an error at the table. */
                if (start_id >= end_id || (end_id - start_id) > U8_MB_CUR_MAX)
                        return ((size_t)sz);

                b3_base = u8_toupper_b3_tbl[uv][b2][b3].base;

                for (i = 0; start_id < end_id; start_id++)
                        u8s[i++] = u8_toupper_final_tbl[uv][b3_base + start_id];
        } else {
                b3_tbl = u8_tolower_b3_tbl[uv][b2][b3].tbl_id;
                if (b3_tbl == U8_TBL_ELEMENT_NOT_DEF)
                        return ((size_t)sz);

                start_id = u8_tolower_b4_tbl[uv][b3_tbl][b4];
                end_id = u8_tolower_b4_tbl[uv][b3_tbl][b4 + 1];

                if (start_id >= end_id || (end_id - start_id) > U8_MB_CUR_MAX)
                        return ((size_t)sz);

                b3_base = u8_tolower_b3_tbl[uv][b2][b3].base;

                for (i = 0; start_id < end_id; start_id++)
                        u8s[i++] = u8_tolower_final_tbl[uv][b3_base + start_id];
        }

        /*
         * If i is still zero, that means there is no corresponding character.
         */
        if (i == 0)
                return ((size_t)sz);

        u8s[i] = '\0';

        return (i);
}

/*
 * The do_case_compare() function compares the two input strings, s1 and s2,
 * one character at a time doing case conversions if applicable and return
 * the comparison result as like strcmp().
 *
 * Since, in empirical sense, most of text data are 7-bit ASCII characters,
 * we treat the 7-bit ASCII characters as a special case trying to yield
 * faster processing time.
 */
static int
do_case_compare(size_t uv, uchar_t *s1, uchar_t *s2, size_t n1,
    size_t n2, boolean_t is_it_toupper, int *errnum)
{
        int f;
        int sz1;
        int sz2;
        size_t j;
        size_t i1;
        size_t i2;
        uchar_t u8s1[U8_MB_CUR_MAX + 1];
        uchar_t u8s2[U8_MB_CUR_MAX + 1];

        i1 = i2 = 0;
        while (i1 < n1 && i2 < n2) {
                /*
                 * Find out what would be the byte length for this UTF-8
                 * character at string s1 and also find out if this is
                 * an illegal start byte or not and if so, issue a proper
                 * error number and yet treat this byte as a character.
                 */
                sz1 = u8_number_of_bytes[*s1];
                if (sz1 < 0) {
                        *errnum = EILSEQ;
                        sz1 = 1;
                }

                /*
                 * For 7-bit ASCII characters mainly, we do a quick case
                 * conversion right at here.
                 *
                 * If we don't have enough bytes for this character, issue
                 * an EINVAL error and use what are available.
                 *
                 * If we have enough bytes, find out if there is
                 * a corresponding uppercase character and if so, copy over
                 * the bytes for a comparison later. If there is no
                 * corresponding uppercase character, then, use what we have
                 * for the comparison.
                 */
                if (sz1 == 1) {
                        if (is_it_toupper)
                                u8s1[0] = U8_ASCII_TOUPPER(*s1);
                        else
                                u8s1[0] = U8_ASCII_TOLOWER(*s1);
                        s1++;
                        u8s1[1] = '\0';
                } else if ((i1 + sz1) > n1) {
                        *errnum = EINVAL;
                        for (j = 0; (i1 + j) < n1; )
                                u8s1[j++] = *s1++;
                        u8s1[j] = '\0';
                } else {
                        (void) do_case_conv(uv, u8s1, s1, sz1, is_it_toupper);
                        s1 += sz1;
                }

                /* Do the same for the string s2. */
                sz2 = u8_number_of_bytes[*s2];
                if (sz2 < 0) {
                        *errnum = EILSEQ;
                        sz2 = 1;
                }

                if (sz2 == 1) {
                        if (is_it_toupper)
                                u8s2[0] = U8_ASCII_TOUPPER(*s2);
                        else
                                u8s2[0] = U8_ASCII_TOLOWER(*s2);
                        s2++;
                        u8s2[1] = '\0';
                } else if ((i2 + sz2) > n2) {
                        *errnum = EINVAL;
                        for (j = 0; (i2 + j) < n2; )
                                u8s2[j++] = *s2++;
                        u8s2[j] = '\0';
                } else {
                        (void) do_case_conv(uv, u8s2, s2, sz2, is_it_toupper);
                        s2 += sz2;
                }

                /* Now compare the two characters. */
                if (sz1 == 1 && sz2 == 1) {
                        if (*u8s1 > *u8s2)
                                return (1);
                        if (*u8s1 < *u8s2)
                                return (-1);
                } else {
                        f = strcmp((const char *)u8s1, (const char *)u8s2);
                        if (f != 0)
                                return (f);
                }

                /*
                 * They were the same. Let's move on to the next
                 * characters then.
                 */
                i1 += sz1;
                i2 += sz2;
        }

        /*
         * We compared until the end of either or both strings.
         *
         * If we reached to or went over the ends for the both, that means
         * they are the same.
         *
         * If we reached only one of the two ends, that means the other string
         * has something which then the fact can be used to determine
         * the return value.
         */
        if (i1 >= n1) {
                if (i2 >= n2)
                        return (0);
                return (-1);
        }
        return (1);
}

/*
 * The combining_class() function checks on the given bytes and find out
 * the corresponding Unicode combining class value. The return value 0 means
 * it is a Starter. Any illegal UTF-8 character will also be treated as
 * a Starter.
 */
static uchar_t
combining_class(size_t uv, uchar_t *s, size_t sz)
{
        uint16_t b1 = 0;
        uint16_t b2 = 0;
        uint16_t b3 = 0;
        uint16_t b4 = 0;

        if (sz == 1 || sz > 4)
                return (0);

        if (sz == 2) {
                b3 = s[0];
                b4 = s[1];
        } else if (sz == 3) {
                b2 = s[0];
                b3 = s[1];
                b4 = s[2];
        } else if (sz == 4) {
                b1 = s[0];
                b2 = s[1];
                b3 = s[2];
                b4 = s[3];
        }

        b1 = u8_common_b1_tbl[uv][b1];
        if (b1 == U8_TBL_ELEMENT_NOT_DEF)
                return (0);

        b2 = u8_combining_class_b2_tbl[uv][b1][b2];
        if (b2 == U8_TBL_ELEMENT_NOT_DEF)
                return (0);

        b3 = u8_combining_class_b3_tbl[uv][b2][b3];
        if (b3 == U8_TBL_ELEMENT_NOT_DEF)
                return (0);

        return (u8_combining_class_b4_tbl[uv][b3][b4]);
}

/*
 * The do_decomp() function finds out a matching decomposition if any
 * and return. If there is no match, the input bytes are copied and returned.
 * The function also checks if there is a Hangul, decomposes it if necessary
 * and returns.
 *
 * To save time, a single byte 7-bit ASCII character should be handled by
 * the caller.
 *
 * The function returns the number of bytes returned sans always terminating
 * the null byte. It will also return a state that will tell if there was
 * a Hangul character decomposed which then will be used by the caller.
 */
static size_t
do_decomp(size_t uv, uchar_t *u8s, uchar_t *s, int sz,
    boolean_t canonical_decomposition, u8_normalization_states_t *state)
{
        uint16_t b1 = 0;
        uint16_t b2 = 0;
        uint16_t b3 = 0;
        uint16_t b3_tbl;
        uint16_t b3_base;
        uint16_t b4 = 0;
        size_t start_id;
        size_t end_id;
        size_t i;
        uint32_t u1;

        if (sz == 2) {
                b3 = u8s[0] = s[0];
                b4 = u8s[1] = s[1];
                u8s[2] = '\0';
        } else if (sz == 3) {
                /* Convert it to a Unicode scalar value. */
                U8_PUT_3BYTES_INTO_UTF32(u1, s[0], s[1], s[2]);

                /*
                 * If this is a Hangul syllable, we decompose it into
                 * a leading consonant, a vowel, and an optional trailing
                 * consonant and then return.
                 */
                if (U8_HANGUL_SYLLABLE(u1)) {
                        u1 -= U8_HANGUL_SYL_FIRST;

                        b1 = U8_HANGUL_JAMO_L_FIRST + u1 / U8_HANGUL_VT_COUNT;
                        b2 = U8_HANGUL_JAMO_V_FIRST + (u1 % U8_HANGUL_VT_COUNT)
                            / U8_HANGUL_T_COUNT;
                        b3 = u1 % U8_HANGUL_T_COUNT;

                        U8_SAVE_HANGUL_AS_UTF8(u8s, 0, 1, 2, b1);
                        U8_SAVE_HANGUL_AS_UTF8(u8s, 3, 4, 5, b2);
                        if (b3) {
                                b3 += U8_HANGUL_JAMO_T_FIRST;
                                U8_SAVE_HANGUL_AS_UTF8(u8s, 6, 7, 8, b3);

                                u8s[9] = '\0';
                                *state = U8_STATE_HANGUL_LVT;
                                return (9);
                        }

                        u8s[6] = '\0';
                        *state = U8_STATE_HANGUL_LV;
                        return (6);
                }

                b2 = u8s[0] = s[0];
                b3 = u8s[1] = s[1];
                b4 = u8s[2] = s[2];
                u8s[3] = '\0';

                /*
                 * If this is a Hangul Jamo, we know there is nothing
                 * further that we can decompose.
                 */
                if (U8_HANGUL_JAMO_L(u1)) {
                        *state = U8_STATE_HANGUL_L;
                        return (3);
                }

                if (U8_HANGUL_JAMO_V(u1)) {
                        if (*state == U8_STATE_HANGUL_L)
                                *state = U8_STATE_HANGUL_LV;
                        else
                                *state = U8_STATE_HANGUL_V;
                        return (3);
                }

                if (U8_HANGUL_JAMO_T(u1)) {
                        if (*state == U8_STATE_HANGUL_LV)
                                *state = U8_STATE_HANGUL_LVT;
                        else
                                *state = U8_STATE_HANGUL_T;
                        return (3);
                }
        } else if (sz == 4) {
                b1 = u8s[0] = s[0];
                b2 = u8s[1] = s[1];
                b3 = u8s[2] = s[2];
                b4 = u8s[3] = s[3];
                u8s[4] = '\0';
        } else {
                /*
                 * This is a fallback and should not happen if the function
                 * was called properly.
                 */
                u8s[0] = s[0];
                u8s[1] = '\0';
                *state = U8_STATE_START;
                return (1);
        }

        /*
         * At this point, this rountine does not know what it would get.
         * The caller should sort it out if the state isn't a Hangul one.
         */
        *state = U8_STATE_START;

        /* Try to find matching decomposition mapping byte sequence. */
        b1 = u8_common_b1_tbl[uv][b1];
        if (b1 == U8_TBL_ELEMENT_NOT_DEF)
                return ((size_t)sz);

        b2 = u8_decomp_b2_tbl[uv][b1][b2];
        if (b2 == U8_TBL_ELEMENT_NOT_DEF)
                return ((size_t)sz);

        b3_tbl = u8_decomp_b3_tbl[uv][b2][b3].tbl_id;
        if (b3_tbl == U8_TBL_ELEMENT_NOT_DEF)
                return ((size_t)sz);

        /*
         * If b3_tbl is bigger than or equal to U8_16BIT_TABLE_INDICATOR
         * which is 0x8000, this means we couldn't fit the mappings into
         * the cardinality of a unsigned byte.
         */
        if (b3_tbl >= U8_16BIT_TABLE_INDICATOR) {
                b3_tbl -= U8_16BIT_TABLE_INDICATOR;
                start_id = u8_decomp_b4_16bit_tbl[uv][b3_tbl][b4];
                end_id = u8_decomp_b4_16bit_tbl[uv][b3_tbl][b4 + 1];
        } else {
                if (b3_tbl >= ARRAY_SIZE(u8_decomp_b4_tbl[uv]))
                        return ((size_t)sz);
                start_id = u8_decomp_b4_tbl[uv][b3_tbl][b4];
                end_id = u8_decomp_b4_tbl[uv][b3_tbl][b4 + 1];
        }

        /* This also means there wasn't any matching decomposition. */
        if (start_id >= end_id)
                return ((size_t)sz);

        /*
         * The final table for decomposition mappings has three types of
         * byte sequences depending on whether a mapping is for compatibility
         * decomposition, canonical decomposition, or both like the following:
         *
         * (1) Compatibility decomposition mappings:
         *
         *      +---+---+-...-+---+
         *      | B0| B1| ... | Bm|
         *      +---+---+-...-+---+
         *
         *      The first byte, B0, is always less then 0xF5 (U8_DECOMP_BOTH).
         *
         * (2) Canonical decomposition mappings:
         *
         *      +---+---+---+-...-+---+
         *      | T | b0| b1| ... | bn|
         *      +---+---+---+-...-+---+
         *
         *      where the first byte, T, is 0xF6 (U8_DECOMP_CANONICAL).
         *
         * (3) Both mappings:
         *
         *      +---+---+---+---+-...-+---+---+---+-...-+---+
         *      | T | D | b0| b1| ... | bn| B0| B1| ... | Bm|
         *      +---+---+---+---+-...-+---+---+---+-...-+---+
         *
         *      where T is 0xF5 (U8_DECOMP_BOTH) and D is a displacement
         *      byte, b0 to bn are canonical mapping bytes and B0 to Bm are
         *      compatibility mapping bytes.
         *
         * Note that compatibility decomposition means doing recursive
         * decompositions using both compatibility decomposition mappings and
         * canonical decomposition mappings. On the other hand, canonical
         * decomposition means doing recursive decompositions using only
         * canonical decomposition mappings. Since the table we have has gone
         * through the recursions already, we do not need to do so during
         * runtime, i.e., the table has been completely flattened out
         * already.
         */

        b3_base = u8_decomp_b3_tbl[uv][b2][b3].base;

        /* Get the type, T, of the byte sequence. */
        b1 = u8_decomp_final_tbl[uv][b3_base + start_id];

        /*
         * If necessary, adjust start_id, end_id, or both. Note that if
         * this is compatibility decomposition mapping, there is no
         * adjustment.
         */
        if (canonical_decomposition) {
                /* Is the mapping only for compatibility decomposition? */
                if (b1 < U8_DECOMP_BOTH)
                        return ((size_t)sz);

                start_id++;

                if (b1 == U8_DECOMP_BOTH) {
                        end_id = start_id +
                            u8_decomp_final_tbl[uv][b3_base + start_id];
                        start_id++;
                }
        } else {
                /*
                 * Unless this is a compatibility decomposition mapping,
                 * we adjust the start_id.
                 */
                if (b1 == U8_DECOMP_BOTH) {
                        start_id++;
                        start_id += u8_decomp_final_tbl[uv][b3_base + start_id];
                } else if (b1 == U8_DECOMP_CANONICAL) {
                        start_id++;
                }
        }

        for (i = 0; start_id < end_id; start_id++)
                u8s[i++] = u8_decomp_final_tbl[uv][b3_base + start_id];
        u8s[i] = '\0';

        return (i);
}

/*
 * The find_composition_start() function uses the character bytes given and
 * find out the matching composition mappings if any and return the address
 * to the composition mappings as explained in the do_composition().
 */
static uchar_t *
find_composition_start(size_t uv, uchar_t *s, size_t sz)
{
        uint16_t b1 = 0;
        uint16_t b2 = 0;
        uint16_t b3 = 0;
        uint16_t b3_tbl;
        uint16_t b3_base;
        uint16_t b4 = 0;
        size_t start_id;
        size_t end_id;

        if (sz == 1) {
                b4 = s[0];
        } else if (sz == 2) {
                b3 = s[0];
                b4 = s[1];
        } else if (sz == 3) {
                b2 = s[0];
                b3 = s[1];
                b4 = s[2];
        } else if (sz == 4) {
                b1 = s[0];
                b2 = s[1];
                b3 = s[2];
                b4 = s[3];
        } else {
                /*
                 * This is a fallback and should not happen if the function
                 * was called properly.
                 */
                return (NULL);
        }

        b1 = u8_composition_b1_tbl[uv][b1];
        if (b1 == U8_TBL_ELEMENT_NOT_DEF)
                return (NULL);

        b2 = u8_composition_b2_tbl[uv][b1][b2];
        if (b2 == U8_TBL_ELEMENT_NOT_DEF)
                return (NULL);

        b3_tbl = u8_composition_b3_tbl[uv][b2][b3].tbl_id;
        if (b3_tbl == U8_TBL_ELEMENT_NOT_DEF)
                return (NULL);

        if (b3_tbl >= U8_16BIT_TABLE_INDICATOR) {
                b3_tbl -= U8_16BIT_TABLE_INDICATOR;
                start_id = u8_composition_b4_16bit_tbl[uv][b3_tbl][b4];
                end_id = u8_composition_b4_16bit_tbl[uv][b3_tbl][b4 + 1];
        } else {
                if (b3_tbl >= ARRAY_SIZE(u8_composition_b4_tbl[uv]))
                        return (NULL);
                start_id = u8_composition_b4_tbl[uv][b3_tbl][b4];
                end_id = u8_composition_b4_tbl[uv][b3_tbl][b4 + 1];
        }

        if (start_id >= end_id)
                return (NULL);

        b3_base = u8_composition_b3_tbl[uv][b2][b3].base;

        return ((uchar_t *)&(u8_composition_final_tbl[uv][b3_base + start_id]));
}

/*
 * The blocked() function checks on the combining class values of previous
 * characters in this sequence and return whether it is blocked or not.
 */
static boolean_t
blocked(uchar_t *comb_class, size_t last)
{
        uchar_t my_comb_class;
        size_t i;

        my_comb_class = comb_class[last];
        for (i = 1; i < last; i++)
                if (comb_class[i] >= my_comb_class ||
                    comb_class[i] == U8_COMBINING_CLASS_STARTER)
                        return (B_TRUE);

        return (B_FALSE);
}

/*
 * The do_composition() reads the character string pointed by 's' and
 * do necessary canonical composition and then copy over the result back to
 * the 's'.
 *
 * The input argument 's' cannot contain more than 32 characters.
 */
static size_t
do_composition(size_t uv, uchar_t *s, uchar_t *comb_class, uchar_t *start,
    uchar_t *disp, size_t last, uchar_t **os, uchar_t *oslast)
{
        uchar_t t[U8_STREAM_SAFE_TEXT_MAX + 1];
        uchar_t tc[U8_MB_CUR_MAX];
        uint8_t saved_marks[U8_MAX_CHARS_A_SEQ];
        size_t saved_marks_count;
        uchar_t *p;
        uchar_t *saved_p;
        uchar_t *q;
        size_t i;
        size_t saved_i;
        size_t j;
        size_t k;
        size_t l;
        size_t C;
        size_t saved_l;
        size_t size;
        uint32_t u1;
        uint32_t u2;
        boolean_t match_not_found = B_TRUE;

        /*
         * This should never happen unless the callers are doing some strange
         * and unexpected things.
         *
         * The "last" is the index pointing to the last character not last + 1.
         */
        if (last >= U8_MAX_CHARS_A_SEQ)
                last = U8_UPPER_LIMIT_IN_A_SEQ;

        for (i = l = 0; i <= last; i++) {
                /*
                 * The last or any non-Starters at the beginning, we don't
                 * have any chance to do composition and so we just copy them
                 * to the temporary buffer.
                 */
                if (i >= last || comb_class[i] != U8_COMBINING_CLASS_STARTER) {
SAVE_THE_CHAR:
                        p = s + start[i];
                        size = disp[i];
                        for (k = 0; k < size; k++)
                                t[l++] = *p++;
                        continue;
                }

                /*
                 * If this could be a start of Hangul Jamos, then, we try to
                 * conjoin them.
                 */
                if (s[start[i]] == U8_HANGUL_JAMO_1ST_BYTE) {
                        U8_PUT_3BYTES_INTO_UTF32(u1, s[start[i]],
                            s[start[i] + 1], s[start[i] + 2]);
                        U8_PUT_3BYTES_INTO_UTF32(u2, s[start[i] + 3],
                            s[start[i] + 4], s[start[i] + 5]);

                        if (U8_HANGUL_JAMO_L(u1) && U8_HANGUL_JAMO_V(u2)) {
                                u1 -= U8_HANGUL_JAMO_L_FIRST;
                                u2 -= U8_HANGUL_JAMO_V_FIRST;
                                u1 = U8_HANGUL_SYL_FIRST +
                                    (u1 * U8_HANGUL_V_COUNT + u2) *
                                    U8_HANGUL_T_COUNT;

                                i += 2;
                                if (i <= last) {
                                        U8_PUT_3BYTES_INTO_UTF32(u2,
                                            s[start[i]], s[start[i] + 1],
                                            s[start[i] + 2]);

                                        if (U8_HANGUL_JAMO_T(u2)) {
                                                u1 += u2 -
                                                    U8_HANGUL_JAMO_T_FIRST;
                                                i++;
                                        }
                                }

                                U8_SAVE_HANGUL_AS_UTF8(t + l, 0, 1, 2, u1);
                                i--;
                                l += 3;
                                continue;
                        }
                }

                /*
                 * Let's then find out if this Starter has composition
                 * mapping.
                 */
                p = find_composition_start(uv, s + start[i], disp[i]);
                if (p == NULL)
                        goto SAVE_THE_CHAR;

                /*
                 * We have a Starter with composition mapping and the next
                 * character is a non-Starter. Let's try to find out if
                 * we can do composition.
                 */

                saved_p = p;
                saved_i = i;
                saved_l = l;
                saved_marks_count = 0;

TRY_THE_NEXT_MARK:
                q = s + start[++i];
                size = disp[i];

                /*
                 * The next for() loop compares the non-Starter pointed by
                 * 'q' with the possible (joinable) characters pointed by 'p'.
                 *
                 * The composition final table entry pointed by the 'p'
                 * looks like the following:
                 *
                 * +---+---+---+-...-+---+---+---+---+-...-+---+---+
                 * | C | b0| b2| ... | bn| F | B0| B1| ... | Bm| F |
                 * +---+---+---+-...-+---+---+---+---+-...-+---+---+
                 *
                 * where C is the count byte indicating the number of
                 * mapping pairs where each pair would be look like
                 * (b0-bn F, B0-Bm F). The b0-bn are the bytes of the second
                 * character of a canonical decomposition and the B0-Bm are
                 * the bytes of a matching composite character. The F is
                 * a filler byte after each character as the separator.
                 */

                match_not_found = B_TRUE;

                for (C = *p++; C > 0; C--) {
                        for (k = 0; k < size; p++, k++)
                                if (*p != q[k])
                                        break;

                        /* Have we found it? */
                        if (k >= size && *p == U8_TBL_ELEMENT_FILLER) {
                                match_not_found = B_FALSE;

                                l = saved_l;

                                while (*++p != U8_TBL_ELEMENT_FILLER)
                                        t[l++] = *p;

                                break;
                        }

                        /* We didn't find; skip to the next pair. */
                        if (*p != U8_TBL_ELEMENT_FILLER)
                                while (*++p != U8_TBL_ELEMENT_FILLER)
                                        ;
                        while (*++p != U8_TBL_ELEMENT_FILLER)
                                ;
                        p++;
                }

                /*
                 * If there was no match, we will need to save the combining
                 * mark for later appending. After that, if the next one
                 * is a non-Starter and not blocked, then, we try once
                 * again to do composition with the next non-Starter.
                 *
                 * If there was no match and this was a Starter, then,
                 * this is a new start.
                 *
                 * If there was a match and a composition done and we have
                 * more to check on, then, we retrieve a new composition final
                 * table entry for the composite and then try to do the
                 * composition again.
                 */

                if (match_not_found) {
                        if (comb_class[i] == U8_COMBINING_CLASS_STARTER) {
                                i--;
                                goto SAVE_THE_CHAR;
                        }

                        saved_marks[saved_marks_count++] = i;
                }

                if (saved_l == l) {
                        while (i < last) {
                                if (blocked(comb_class, i + 1))
                                        saved_marks[saved_marks_count++] = ++i;
                                else
                                        break;
                        }
                        if (i < last) {
                                p = saved_p;
                                goto TRY_THE_NEXT_MARK;
                        }
                } else if (i < last) {
                        p = find_composition_start(uv, t + saved_l,
                            l - saved_l);
                        if (p != NULL) {
                                saved_p = p;
                                goto TRY_THE_NEXT_MARK;
                        }
                }

                /*
                 * There is no more composition possible.
                 *
                 * If there was no composition what so ever then we copy
                 * over the original Starter and then append any non-Starters
                 * remaining at the target string sequentially after that.
                 */

                if (saved_l == l) {
                        p = s + start[saved_i];
                        size = disp[saved_i];
                        for (j = 0; j < size; j++)
                                t[l++] = *p++;
                }

                for (k = 0; k < saved_marks_count; k++) {
                        p = s + start[saved_marks[k]];
                        size = disp[saved_marks[k]];
                        for (j = 0; j < size; j++)
                                t[l++] = *p++;
                }
        }

        /*
         * If the last character is a Starter and if we have a character
         * (possibly another Starter) that can be turned into a composite,
         * we do so and we do so until there is no more of composition
         * possible.
         */
        if (comb_class[last] == U8_COMBINING_CLASS_STARTER) {
                p = *os;
                saved_l = l - disp[last];

                while (p < oslast) {
                        int8_t number_of_bytes = u8_number_of_bytes[*p];

                        if (number_of_bytes <= 1)
                                break;
                        size = number_of_bytes;
                        if ((p + size) > oslast)
                                break;

                        saved_p = p;

                        for (i = 0; i < size; i++)
                                tc[i] = *p++;

                        q = find_composition_start(uv, t + saved_l,
                            l - saved_l);
                        if (q == NULL) {
                                p = saved_p;
                                break;
                        }

                        match_not_found = B_TRUE;

                        for (C = *q++; C > 0; C--) {
                                for (k = 0; k < size; q++, k++)
                                        if (*q != tc[k])
                                                break;

                                if (k >= size && *q == U8_TBL_ELEMENT_FILLER) {
                                        match_not_found = B_FALSE;

                                        l = saved_l;

                                        while (*++q != U8_TBL_ELEMENT_FILLER) {
                                                /*
                                                 * This is practically
                                                 * impossible but we don't
                                                 * want to take any chances.
                                                 */
                                                if (l >=
                                                    U8_STREAM_SAFE_TEXT_MAX) {
                                                        p = saved_p;
                                                        goto SAFE_RETURN;
                                                }
                                                t[l++] = *q;
                                        }

                                        break;
                                }

                                if (*q != U8_TBL_ELEMENT_FILLER)
                                        while (*++q != U8_TBL_ELEMENT_FILLER)
                                                ;
                                while (*++q != U8_TBL_ELEMENT_FILLER)
                                        ;
                                q++;
                        }

                        if (match_not_found) {
                                p = saved_p;
                                break;
                        }
                }
SAFE_RETURN:
                *os = p;
        }

        /*
         * Now we copy over the temporary string to the target string.
         * Since composition always reduces the number of characters or
         * the number of characters stay, we don't need to worry about
         * the buffer overflow here.
         */
        for (i = 0; i < l; i++)
                s[i] = t[i];
        s[l] = '\0';

        return (l);
}

/*
 * The collect_a_seq() function checks on the given string s, collect
 * a sequence of characters at u8s, and return the sequence. While it collects
 * a sequence, it also applies case conversion, canonical or compatibility
 * decomposition, canonical decomposition, or some or all of them and
 * in that order.
 *
 * The collected sequence cannot be bigger than 32 characters since if
 * it is having more than 31 characters, the sequence will be terminated
 * with a U+034F COMBINING GRAPHEME JOINER (CGJ) character and turned into
 * a Stream-Safe Text. The collected sequence is always terminated with
 * a null byte and the return value is the byte length of the sequence
 * including 0. The return value does not include the terminating
 * null byte.
 */
static size_t
collect_a_seq(size_t uv, uchar_t *u8s, uchar_t **source, uchar_t *slast,
    boolean_t is_it_toupper,
    boolean_t is_it_tolower,
    boolean_t canonical_decomposition,
    boolean_t compatibility_decomposition,
    boolean_t canonical_composition,
    int *errnum, u8_normalization_states_t *state)
{
        uchar_t *s;
        int sz;
        int saved_sz;
        size_t i;
        size_t j;
        size_t k;
        size_t l;
        uchar_t comb_class[U8_MAX_CHARS_A_SEQ];
        uchar_t disp[U8_MAX_CHARS_A_SEQ];
        uchar_t start[U8_MAX_CHARS_A_SEQ];
        uchar_t u8t[U8_MB_CUR_MAX];
        uchar_t uts[U8_STREAM_SAFE_TEXT_MAX + 1];
        uchar_t tc;
        size_t last;
        size_t saved_last;
        uint32_t u1;

        /*
         * Save the source string pointer which we will return a changed
         * pointer if we do processing.
         */
        s = *source;

        /*
         * The following is a fallback for just in case callers are not
         * checking the string boundaries before the calling.
         */
        if (s >= slast) {
                u8s[0] = '\0';

                return (0);
        }

        /*
         * As the first thing, let's collect a character and do case
         * conversion if necessary.
         */

        sz = u8_number_of_bytes[*s];

        if (sz < 0) {
                *errnum = EILSEQ;

                u8s[0] = *s++;
                u8s[1] = '\0';

                *source = s;

                return (1);
        }

        if (sz == 1) {
                if (is_it_toupper)
                        u8s[0] = U8_ASCII_TOUPPER(*s);
                else if (is_it_tolower)
                        u8s[0] = U8_ASCII_TOLOWER(*s);
                else
                        u8s[0] = *s;
                s++;
                u8s[1] = '\0';
        } else if ((s + sz) > slast) {
                *errnum = EINVAL;

                for (i = 0; s < slast; )
                        u8s[i++] = *s++;
                u8s[i] = '\0';

                *source = s;

                return (i);
        } else {
                if (is_it_toupper || is_it_tolower) {
                        i = do_case_conv(uv, u8s, s, sz, is_it_toupper);
                        s += sz;
                        sz = i;
                } else {
                        for (i = 0; i < sz; )
                                u8s[i++] = *s++;
                        u8s[i] = '\0';
                }
        }

        /*
         * And then canonical/compatibility decomposition followed by
         * an optional canonical composition. Please be noted that
         * canonical composition is done only when a decomposition is
         * done.
         */
        if (canonical_decomposition || compatibility_decomposition) {
                if (sz == 1) {
                        *state = U8_STATE_START;

                        saved_sz = 1;

                        comb_class[0] = 0;
                        start[0] = 0;
                        disp[0] = 1;

                        last = 1;
                } else {
                        saved_sz = do_decomp(uv, u8s, u8s, sz,
                            canonical_decomposition, state);

                        last = 0;

                        for (i = 0; i < saved_sz; ) {
                                sz = u8_number_of_bytes[u8s[i]];

                                comb_class[last] = combining_class(uv,
                                    u8s + i, sz);
                                start[last] = i;
                                disp[last] = sz;

                                last++;
                                i += sz;
                        }

                        /*
                         * Decomposition yields various Hangul related
                         * states but not on combining marks. We need to
                         * find out at here by checking on the last
                         * character.
                         */
                        if (*state == U8_STATE_START) {
                                if (comb_class[last - 1])
                                        *state = U8_STATE_COMBINING_MARK;
                        }
                }

                saved_last = last;

                while (s < slast) {
                        sz = u8_number_of_bytes[*s];

                        /*
                         * If this is an illegal character, an incomplete
                         * character, or an 7-bit ASCII Starter character,
                         * then we have collected a sequence; break and let
                         * the next call deal with the two cases.
                         *
                         * Note that this is okay only if you are using this
                         * function with a fixed length string, not on
                         * a buffer with multiple calls of one chunk at a time.
                         */
                        if (sz <= 1) {
                                break;
                        } else if ((s + sz) > slast) {
                                break;
                        } else {
                                /*
                                 * If the previous character was a Hangul Jamo
                                 * and this character is a Hangul Jamo that
                                 * can be conjoined, we collect the Jamo.
                                 */
                                if (*s == U8_HANGUL_JAMO_1ST_BYTE) {
                                        U8_PUT_3BYTES_INTO_UTF32(u1,
                                            *s, *(s + 1), *(s + 2));

                                        if (U8_HANGUL_COMPOSABLE_L_V(*state,
                                            u1)) {
                                                i = 0;
                                                *state = U8_STATE_HANGUL_LV;
                                                goto COLLECT_A_HANGUL;
                                        }

                                        if (U8_HANGUL_COMPOSABLE_LV_T(*state,
                                            u1)) {
                                                i = 0;
                                                *state = U8_STATE_HANGUL_LVT;
                                                goto COLLECT_A_HANGUL;
                                        }
                                }

                                /*
                                 * Regardless of whatever it was, if this is
                                 * a Starter, we don't collect the character
                                 * since that's a new start and we will deal
                                 * with it at the next time.
                                 */
                                i = combining_class(uv, s, sz);
                                if (i == U8_COMBINING_CLASS_STARTER)
                                        break;

                                /*
                                 * We know the current character is a combining
                                 * mark. If the previous character wasn't
                                 * a Starter (not Hangul) or a combining mark,
                                 * then, we don't collect this combining mark.
                                 */
                                if (*state != U8_STATE_START &&
                                    *state != U8_STATE_COMBINING_MARK)
                                        break;

                                *state = U8_STATE_COMBINING_MARK;
COLLECT_A_HANGUL:
                                /*
                                 * If we collected a Starter and combining
                                 * marks up to 30, i.e., total 31 characters,
                                 * then, we terminate this degenerately long
                                 * combining sequence with a U+034F COMBINING
                                 * GRAPHEME JOINER (CGJ) which is 0xCD 0x8F in
                                 * UTF-8 and turn this into a Stream-Safe
                                 * Text. This will be extremely rare but
                                 * possible.
                                 *
                                 * The following will also guarantee that
                                 * we are not writing more than 32 characters
                                 * plus a NULL at u8s[].
                                 */
                                if (last >= U8_UPPER_LIMIT_IN_A_SEQ) {
TURN_STREAM_SAFE:
                                        *state = U8_STATE_START;
                                        comb_class[last] = 0;
                                        start[last] = saved_sz;
                                        disp[last] = 2;
                                        last++;

                                        u8s[saved_sz++] = 0xCD;
                                        u8s[saved_sz++] = 0x8F;

                                        break;
                                }

                                /*
                                 * Some combining marks also do decompose into
                                 * another combining mark or marks.
                                 */
                                if (*state == U8_STATE_COMBINING_MARK) {
                                        k = last;
                                        l = sz;
                                        i = do_decomp(uv, uts, s, sz,
                                            canonical_decomposition, state);
                                        for (j = 0; j < i; ) {
                                                sz = u8_number_of_bytes[uts[j]];

                                                comb_class[last] =
                                                    combining_class(uv,
                                                    uts + j, sz);
                                                start[last] = saved_sz + j;
                                                disp[last] = sz;

                                                last++;
                                                if (last >=
                                                    U8_UPPER_LIMIT_IN_A_SEQ) {
                                                        last = k;
                                                        goto TURN_STREAM_SAFE;
                                                }
                                                j += sz;
                                        }

                                        *state = U8_STATE_COMBINING_MARK;
                                        sz = i;
                                        s += l;

                                        for (i = 0; i < sz; i++)
                                                u8s[saved_sz++] = uts[i];
                                } else {
                                        comb_class[last] = i;
                                        start[last] = saved_sz;
                                        disp[last] = sz;
                                        last++;

                                        for (i = 0; i < sz; i++)
                                                u8s[saved_sz++] = *s++;
                                }

                                /*
                                 * If this is U+0345 COMBINING GREEK
                                 * YPOGEGRAMMENI (0xCD 0x85 in UTF-8), a.k.a.,
                                 * iota subscript, and need to be converted to
                                 * uppercase letter, convert it to U+0399 GREEK
                                 * CAPITAL LETTER IOTA (0xCE 0x99 in UTF-8),
                                 * i.e., convert to capital adscript form as
                                 * specified in the Unicode standard.
                                 *
                                 * This is the only special case of (ambiguous)
                                 * case conversion at combining marks and
                                 * probably the standard will never have
                                 * anything similar like this in future.
                                 */
                                if (is_it_toupper && sz >= 2 &&
                                    u8s[saved_sz - 2] == 0xCD &&
                                    u8s[saved_sz - 1] == 0x85) {
                                        u8s[saved_sz - 2] = 0xCE;
                                        u8s[saved_sz - 1] = 0x99;
                                }
                        }
                }

                /*
                 * Let's try to ensure a canonical ordering for the collected
                 * combining marks. We do this only if we have collected
                 * at least one more non-Starter. (The decomposition mapping
                 * data tables have fully (and recursively) expanded and
                 * canonically ordered decompositions.)
                 *
                 * The U8_SWAP_COMB_MARKS() convenience macro has some
                 * assumptions and we are meeting the assumptions.
                 */
                last--;
                if (last >= saved_last) {
                        for (i = 0; i < last; i++)
                                for (j = last; j > i; j--)
                                        if (comb_class[j] &&
                                            comb_class[j - 1] > comb_class[j]) {
                                                U8_SWAP_COMB_MARKS(j - 1, j);
                                        }
                }

                *source = s;

                if (! canonical_composition) {
                        u8s[saved_sz] = '\0';
                        return (saved_sz);
                }

                /*
                 * Now do the canonical composition. Note that we do this
                 * only after a canonical or compatibility decomposition to
                 * finish up NFC or NFKC.
                 */
                sz = do_composition(uv, u8s, comb_class, start, disp, last,
                    &s, slast);
        }

        *source = s;

        return ((size_t)sz);
}

/*
 * The do_norm_compare() function does string comparion based on Unicode
 * simple case mappings and Unicode Normalization definitions.
 *
 * It does so by collecting a sequence of character at a time and comparing
 * the collected sequences from the strings.
 *
 * The meanings on the return values are the same as the usual strcmp().
 */
static int
do_norm_compare(size_t uv, uchar_t *s1, uchar_t *s2, size_t n1, size_t n2,
    int flag, int *errnum)
{
        int result;
        size_t sz1;
        size_t sz2;
        uchar_t u8s1[U8_STREAM_SAFE_TEXT_MAX + 1];
        uchar_t u8s2[U8_STREAM_SAFE_TEXT_MAX + 1];
        uchar_t *s1last;
        uchar_t *s2last;
        boolean_t is_it_toupper;
        boolean_t is_it_tolower;
        boolean_t canonical_decomposition;
        boolean_t compatibility_decomposition;
        boolean_t canonical_composition;
        u8_normalization_states_t state;

        s1last = s1 + n1;
        s2last = s2 + n2;

        is_it_toupper = flag & U8_TEXTPREP_TOUPPER;
        is_it_tolower = flag & U8_TEXTPREP_TOLOWER;
        canonical_decomposition = flag & U8_CANON_DECOMP;
        compatibility_decomposition = flag & U8_COMPAT_DECOMP;
        canonical_composition = flag & U8_CANON_COMP;

        while (s1 < s1last && s2 < s2last) {
                /*
                 * If the current character is a 7-bit ASCII and the last
                 * character, or, if the current character and the next
                 * character are both some 7-bit ASCII characters then
                 * we treat the current character as a sequence.
                 *
                 * In any other cases, we need to call collect_a_seq().
                 */

                if (U8_ISASCII(*s1) && ((s1 + 1) >= s1last ||
                    ((s1 + 1) < s1last && U8_ISASCII(*(s1 + 1))))) {
                        if (is_it_toupper)
                                u8s1[0] = U8_ASCII_TOUPPER(*s1);
                        else if (is_it_tolower)
                                u8s1[0] = U8_ASCII_TOLOWER(*s1);
                        else
                                u8s1[0] = *s1;
                        u8s1[1] = '\0';
                        sz1 = 1;
                        s1++;
                } else {
                        state = U8_STATE_START;
                        sz1 = collect_a_seq(uv, u8s1, &s1, s1last,
                            is_it_toupper, is_it_tolower,
                            canonical_decomposition,
                            compatibility_decomposition,
                            canonical_composition, errnum, &state);
                }

                if (U8_ISASCII(*s2) && ((s2 + 1) >= s2last ||
                    ((s2 + 1) < s2last && U8_ISASCII(*(s2 + 1))))) {
                        if (is_it_toupper)
                                u8s2[0] = U8_ASCII_TOUPPER(*s2);
                        else if (is_it_tolower)
                                u8s2[0] = U8_ASCII_TOLOWER(*s2);
                        else
                                u8s2[0] = *s2;
                        u8s2[1] = '\0';
                        sz2 = 1;
                        s2++;
                } else {
                        state = U8_STATE_START;
                        sz2 = collect_a_seq(uv, u8s2, &s2, s2last,
                            is_it_toupper, is_it_tolower,
                            canonical_decomposition,
                            compatibility_decomposition,
                            canonical_composition, errnum, &state);
                }

                /*
                 * Now compare the two characters. If they are the same,
                 * we move on to the next character sequences.
                 */
                if (sz1 == 1 && sz2 == 1) {
                        if (*u8s1 > *u8s2)
                                return (1);
                        if (*u8s1 < *u8s2)
                                return (-1);
                } else {
                        result = strcmp((const char *)u8s1, (const char *)u8s2);
                        if (result != 0)
                                return (result);
                }
        }

        /*
         * We compared until the end of either or both strings.
         *
         * If we reached to or went over the ends for the both, that means
         * they are the same.
         *
         * If we reached only one end, that means the other string has
         * something which then can be used to determine the return value.
         */
        if (s1 >= s1last) {
                if (s2 >= s2last)
                        return (0);
                return (-1);
        }
        return (1);
}

/*
 * The u8_strcmp() function compares two UTF-8 strings quite similar to
 * the strcmp(). For the comparison, however, Unicode Normalization specific
 * equivalency and Unicode simple case conversion mappings based equivalency
 * can be requested and checked against.
 */
int
u8_strcmp(const char *s1, const char *s2, size_t n, int flag, size_t uv,
    int *errnum)
{
        int f;
        size_t n1;
        size_t n2;

        *errnum = 0;

        /*
         * Check on the requested Unicode version, case conversion, and
         * normalization flag values.
         */

        if (uv > U8_UNICODE_LATEST) {
                *errnum = ERANGE;
                uv = U8_UNICODE_LATEST;
        }

        if (flag == 0) {
                flag = U8_STRCMP_CS;
        } else {
                f = flag & (U8_STRCMP_CS | U8_STRCMP_CI_UPPER |
                    U8_STRCMP_CI_LOWER);
                if (f == 0) {
                        flag |= U8_STRCMP_CS;
                } else if (f != U8_STRCMP_CS && f != U8_STRCMP_CI_UPPER &&
                    f != U8_STRCMP_CI_LOWER) {
                        *errnum = EBADF;
                        flag = U8_STRCMP_CS;
                }

                f = flag & (U8_CANON_DECOMP | U8_COMPAT_DECOMP | U8_CANON_COMP);
                if (f && f != U8_STRCMP_NFD && f != U8_STRCMP_NFC &&
                    f != U8_STRCMP_NFKD && f != U8_STRCMP_NFKC) {
                        *errnum = EBADF;
                        flag = U8_STRCMP_CS;
                }
        }

        if (flag == U8_STRCMP_CS) {
                return (n == 0 ? strcmp(s1, s2) : strncmp(s1, s2, n));
        }

        n1 = strlen(s1);
        n2 = strlen(s2);
        if (n != 0) {
                if (n < n1)
                        n1 = n;
                if (n < n2)
                        n2 = n;
        }

        /*
         * Simple case conversion can be done much faster and so we do
         * them separately here.
         */
        if (flag == U8_STRCMP_CI_UPPER) {
                return (do_case_compare(uv, (uchar_t *)s1, (uchar_t *)s2,
                    n1, n2, B_TRUE, errnum));
        } else if (flag == U8_STRCMP_CI_LOWER) {
                return (do_case_compare(uv, (uchar_t *)s1, (uchar_t *)s2,
                    n1, n2, B_FALSE, errnum));
        }

        return (do_norm_compare(uv, (uchar_t *)s1, (uchar_t *)s2, n1, n2,
            flag, errnum));
}

size_t
u8_textprep_str(char *inarray, size_t *inlen, char *outarray, size_t *outlen,
    int flag, size_t unicode_version, int *errnum)
{
        int f;
        int sz;
        uchar_t *ib;
        uchar_t *ibtail;
        uchar_t *ob;
        uchar_t *obtail;
        boolean_t do_not_ignore_null;
        boolean_t do_not_ignore_invalid;
        boolean_t is_it_toupper;
        boolean_t is_it_tolower;
        boolean_t canonical_decomposition;
        boolean_t compatibility_decomposition;
        boolean_t canonical_composition;
        size_t ret_val;
        size_t i;
        size_t j;
        uchar_t u8s[U8_STREAM_SAFE_TEXT_MAX + 1];
        u8_normalization_states_t state;

        if (unicode_version > U8_UNICODE_LATEST) {
                *errnum = ERANGE;
                return ((size_t)-1);
        }

        f = flag & (U8_TEXTPREP_TOUPPER | U8_TEXTPREP_TOLOWER);
        if (f == (U8_TEXTPREP_TOUPPER | U8_TEXTPREP_TOLOWER)) {
                *errnum = EBADF;
                return ((size_t)-1);
        }

        f = flag & (U8_CANON_DECOMP | U8_COMPAT_DECOMP | U8_CANON_COMP);
        if (f && f != U8_TEXTPREP_NFD && f != U8_TEXTPREP_NFC &&
            f != U8_TEXTPREP_NFKD && f != U8_TEXTPREP_NFKC) {
                *errnum = EBADF;
                return ((size_t)-1);
        }

        if (inarray == NULL || *inlen == 0)
                return (0);

        if (outarray == NULL) {
                *errnum = E2BIG;
                return ((size_t)-1);
        }

        ib = (uchar_t *)inarray;
        ob = (uchar_t *)outarray;
        ibtail = ib + *inlen;
        obtail = ob + *outlen;

        do_not_ignore_null = !(flag & U8_TEXTPREP_IGNORE_NULL);
        do_not_ignore_invalid = !(flag & U8_TEXTPREP_IGNORE_INVALID);
        is_it_toupper = flag & U8_TEXTPREP_TOUPPER;
        is_it_tolower = flag & U8_TEXTPREP_TOLOWER;

        ret_val = 0;

        /*
         * If we don't have a normalization flag set, we do the simple case
         * conversion based text preparation separately below. Text
         * preparation involving Normalization will be done in the false task
         * block, again, separately since it will take much more time and
         * resource than doing simple case conversions.
         */
        if (f == 0) {
                while (ib < ibtail) {
                        if (*ib == '\0' && do_not_ignore_null)
                                break;

                        sz = u8_number_of_bytes[*ib];

                        if (sz < 0) {
                                if (do_not_ignore_invalid) {
                                        *errnum = EILSEQ;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                sz = 1;
                                ret_val++;
                        }

                        if (sz == 1) {
                                if (ob >= obtail) {
                                        *errnum = E2BIG;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                if (is_it_toupper)
                                        *ob = U8_ASCII_TOUPPER(*ib);
                                else if (is_it_tolower)
                                        *ob = U8_ASCII_TOLOWER(*ib);
                                else
                                        *ob = *ib;
                                ib++;
                                ob++;
                        } else if ((ib + sz) > ibtail) {
                                if (do_not_ignore_invalid) {
                                        *errnum = EINVAL;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                if ((obtail - ob) < (ibtail - ib)) {
                                        *errnum = E2BIG;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                /*
                                 * We treat the remaining incomplete character
                                 * bytes as a character.
                                 */
                                ret_val++;

                                while (ib < ibtail)
                                        *ob++ = *ib++;
                        } else {
                                if (is_it_toupper || is_it_tolower) {
                                        i = do_case_conv(unicode_version, u8s,
                                            ib, sz, is_it_toupper);

                                        if ((obtail - ob) < i) {
                                                *errnum = E2BIG;
                                                ret_val = (size_t)-1;
                                                break;
                                        }

                                        ib += sz;

                                        for (sz = 0; sz < i; sz++)
                                                *ob++ = u8s[sz];
                                } else {
                                        if ((obtail - ob) < sz) {
                                                *errnum = E2BIG;
                                                ret_val = (size_t)-1;
                                                break;
                                        }

                                        for (i = 0; i < sz; i++)
                                                *ob++ = *ib++;
                                }
                        }
                }
        } else {
                canonical_decomposition = flag & U8_CANON_DECOMP;
                compatibility_decomposition = flag & U8_COMPAT_DECOMP;
                canonical_composition = flag & U8_CANON_COMP;

                while (ib < ibtail) {
                        if (*ib == '\0' && do_not_ignore_null)
                                break;

                        /*
                         * If the current character is a 7-bit ASCII
                         * character and it is the last character, or,
                         * if the current character is a 7-bit ASCII
                         * character and the next character is also a 7-bit
                         * ASCII character, then, we copy over this
                         * character without going through collect_a_seq().
                         *
                         * In any other cases, we need to look further with
                         * the collect_a_seq() function.
                         */
                        if (U8_ISASCII(*ib) && ((ib + 1) >= ibtail ||
                            ((ib + 1) < ibtail && U8_ISASCII(*(ib + 1))))) {
                                if (ob >= obtail) {
                                        *errnum = E2BIG;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                if (is_it_toupper)
                                        *ob = U8_ASCII_TOUPPER(*ib);
                                else if (is_it_tolower)
                                        *ob = U8_ASCII_TOLOWER(*ib);
                                else
                                        *ob = *ib;
                                ib++;
                                ob++;
                        } else {
                                *errnum = 0;
                                state = U8_STATE_START;

                                j = collect_a_seq(unicode_version, u8s,
                                    &ib, ibtail,
                                    is_it_toupper,
                                    is_it_tolower,
                                    canonical_decomposition,
                                    compatibility_decomposition,
                                    canonical_composition,
                                    errnum, &state);

                                if (*errnum && do_not_ignore_invalid) {
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                if ((obtail - ob) < j) {
                                        *errnum = E2BIG;
                                        ret_val = (size_t)-1;
                                        break;
                                }

                                for (i = 0; i < j; i++)
                                        *ob++ = u8s[i];
                        }
                }
        }

        *inlen = ibtail - ib;
        *outlen = obtail - ob;

        return (ret_val);
}