[thirdparty/e2fsprogs.git] / lib / ext2fs / nls_utf8.c

/*
 * Copyright (c) 2014 SGI.
 * Copyright (c) 2018 Collabora Ltd.
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

/*
 * This code is adapted from the Linux Kernel.  We have a
 * userspace version here such that the hashes will match that
 * implementation.
 */

#include "config.h"
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <limits.h>
#include <errno.h>

#include "ext2_fs.h"
#include "ext2fs.h"
#include "ext2fsP.h"

/* Encoding a unicode version number as a single unsigned int. */
#define UNICODE_MAJ_SHIFT               (16)
#define UNICODE_MIN_SHIFT               (8)

#define UNICODE_AGE(MAJ, MIN, REV)                      \
        (((unsigned int)(MAJ) << UNICODE_MAJ_SHIFT) |   \
         ((unsigned int)(MIN) << UNICODE_MIN_SHIFT) |   \
         ((unsigned int)(REV)))

/* Needed in struct utf8cursor below. */
#define UTF8HANGULLEAF  (12)

/*
 * Cursor structure used by the normalizer.
 */
struct utf8cursor {
        const struct utf8data   *data;
        const char      *s;
        const char      *p;
        const char      *ss;
        const char      *sp;
        unsigned int    len;
        unsigned int    slen;
        short int       ccc;
        short int       nccc;
        unsigned char   hangul[UTF8HANGULLEAF];
};

/*
 * Initialize a utf8cursor to normalize a string.
 * Returns 0 on success.
 * Returns -1 on failure.
 */
// extern int utf8cursor(struct utf8cursor *u8c, const struct utf8data *data,
//                    const char *s);
// extern int utf8ncursor(struct utf8cursor *u8c, const struct utf8data *data,
//                     const char *s, size_t len);

/*
 * Get the next byte in the normalization.
 * Returns a value > 0 && < 256 on success.
 * Returns 0 when the end of the normalization is reached.
 * Returns -1 if the string being normalized is not valid UTF-8.
 */
// extern int utf8byte(struct utf8cursor *u8c);


struct utf8data {
        unsigned int maxage;
        unsigned int offset;
};

#define __INCLUDED_FROM_UTF8NORM_C__
#include "utf8data.h"
#undef __INCLUDED_FROM_UTF8NORM_C__

#define ARRAY_SIZE(array)                       \
        (sizeof(array) / sizeof(array[0]))

#if 0
/* Highest unicode version supported by the data tables. */
static int utf8version_is_supported(uint8_t maj, uint8_t min, uint8_t rev)
{
        int i = ARRAY_SIZE(utf8agetab) - 1;
        unsigned int sb_utf8version = UNICODE_AGE(maj, min, rev);

        while (i >= 0 && utf8agetab[i] != 0) {
                if (sb_utf8version == utf8agetab[i])
                        return 1;
                i--;
        }
        return 0;
}
#endif

#if 0
static int utf8version_latest(void)
{
        return utf8vers;
}
#endif

/*
 * UTF-8 valid ranges.
 *
 * The UTF-8 encoding spreads the bits of a 32bit word over several
 * bytes. This table gives the ranges that can be held and how they'd
 * be represented.
 *
 * 0x00000000 0x0000007F: 0xxxxxxx
 * 0x00000000 0x000007FF: 110xxxxx 10xxxxxx
 * 0x00000000 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 *
 * There is an additional requirement on UTF-8, in that only the
 * shortest representation of a 32bit value is to be used.  A decoder
 * must not decode sequences that do not satisfy this requirement.
 * Thus the allowed ranges have a lower bound.
 *
 * 0x00000000 0x0000007F: 0xxxxxxx
 * 0x00000080 0x000007FF: 110xxxxx 10xxxxxx
 * 0x00000800 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
 * 0x00010000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00200000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x04000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 *
 * Actual unicode characters are limited to the range 0x0 - 0x10FFFF,
 * 17 planes of 65536 values.  This limits the sequences actually seen
 * even more, to just the following.
 *
 *          0 -     0x7F: 0                   - 0x7F
 *       0x80 -    0x7FF: 0xC2 0x80           - 0xDF 0xBF
 *      0x800 -   0xFFFF: 0xE0 0xA0 0x80      - 0xEF 0xBF 0xBF
 *    0x10000 - 0x10FFFF: 0xF0 0x90 0x80 0x80 - 0xF4 0x8F 0xBF 0xBF
 *
 * Within those ranges the surrogates 0xD800 - 0xDFFF are not allowed.
 *
 * Note that the longest sequence seen with valid usage is 4 bytes,
 * the same a single UTF-32 character.  This makes the UTF-8
 * representation of Unicode strictly smaller than UTF-32.
 *
 * The shortest sequence requirement was introduced by:
 *    Corrigendum #1: UTF-8 Shortest Form
 * It can be found here:
 *    http://www.unicode.org/versions/corrigendum1.html
 *
 */

/*
 * Return the number of bytes used by the current UTF-8 sequence.
 * Assumes the input points to the first byte of a valid UTF-8
 * sequence.
 */
static inline int utf8clen(const char *s)
{
        unsigned char c = *s;

        return 1 + (c >= 0xC0) + (c >= 0xE0) + (c >= 0xF0);
}

/*
 * Decode a 3-byte UTF-8 sequence.
 */
static unsigned int
utf8decode3(const char *str)
{
        unsigned int            uc;

        uc = *str++ & 0x0F;
        uc <<= 6;
        uc |= *str++ & 0x3F;
        uc <<= 6;
        uc |= *str++ & 0x3F;

        return uc;
}

/*
 * Encode a 3-byte UTF-8 sequence.
 */
static int
utf8encode3(char *str, unsigned int val)
{
        str[2] = (val & 0x3F) | 0x80;
        val >>= 6;
        str[1] = (val & 0x3F) | 0x80;
        val >>= 6;
        str[0] = val | 0xE0;

        return 3;
}

/*
 * utf8trie_t
 *
 * A compact binary tree, used to decode UTF-8 characters.
 *
 * Internal nodes are one byte for the node itself, and up to three
 * bytes for an offset into the tree.  The first byte contains the
 * following information:
 *  NEXTBYTE  - flag        - advance to next byte if set
 *  BITNUM    - 3 bit field - the bit number to tested
 *  OFFLEN    - 2 bit field - number of bytes in the offset
 * if offlen == 0 (non-branching node)
 *  RIGHTPATH - 1 bit field - set if the following node is for the
 *                            right-hand path (tested bit is set)
 *  TRIENODE  - 1 bit field - set if the following node is an internal
 *                            node, otherwise it is a leaf node
 * if offlen != 0 (branching node)
 *  LEFTNODE  - 1 bit field - set if the left-hand node is internal
 *  RIGHTNODE - 1 bit field - set if the right-hand node is internal
 *
 * Due to the way utf8 works, there cannot be branching nodes with
 * NEXTBYTE set, and moreover those nodes always have a righthand
 * descendant.
 */
typedef const unsigned char utf8trie_t;
#define BITNUM          0x07
#define NEXTBYTE        0x08
#define OFFLEN          0x30
#define OFFLEN_SHIFT    4
#define RIGHTPATH       0x40
#define TRIENODE        0x80
#define RIGHTNODE       0x40
#define LEFTNODE        0x80

/*
 * utf8leaf_t
 *
 * The leaves of the trie are embedded in the trie, and so the same
 * underlying datatype: unsigned char.
 *
 * leaf[0]: The unicode version, stored as a generation number that is
 *          an index into utf8agetab[].  With this we can filter code
 *          points based on the unicode version in which they were
 *          defined.  The CCC of a non-defined code point is 0.
 * leaf[1]: Canonical Combining Class. During normalization, we need
 *          to do a stable sort into ascending order of all characters
 *          with a non-zero CCC that occur between two characters with
 *          a CCC of 0, or at the begin or end of a string.
 *          The unicode standard guarantees that all CCC values are
 *          between 0 and 254 inclusive, which leaves 255 available as
 *          a special value.
 *          Code points with CCC 0 are known as stoppers.
 * leaf[2]: Decomposition. If leaf[1] == 255, then leaf[2] is the
 *          start of a NUL-terminated string that is the decomposition
 *          of the character.
 *          The CCC of a decomposable character is the same as the CCC
 *          of the first character of its decomposition.
 *          Some characters decompose as the empty string: these are
 *          characters with the Default_Ignorable_Code_Point property.
 *          These do affect normalization, as they all have CCC 0.
 *
 * The decompositions in the trie have been fully expanded, with the
 * exception of Hangul syllables, which are decomposed algorithmically.
 *
 * Casefolding, if applicable, is also done using decompositions.
 *
 * The trie is constructed in such a way that leaves exist for all
 * UTF-8 sequences that match the criteria from the "UTF-8 valid
 * ranges" comment above, and only for those sequences.  Therefore a
 * lookup in the trie can be used to validate the UTF-8 input.
 */
typedef const unsigned char utf8leaf_t;

#define LEAF_GEN(LEAF)  ((LEAF)[0])
#define LEAF_CCC(LEAF)  ((LEAF)[1])
#define LEAF_STR(LEAF)  ((const char *)((LEAF) + 2))

#define MINCCC          (0)
#define MAXCCC          (254)
#define STOPPER         (0)
#define DECOMPOSE       (255)

/* Marker for hangul syllable decomposition. */
#define HANGUL          ((char)(255))
/* Size of the synthesized leaf used for Hangul syllable decomposition. */
#define UTF8HANGULLEAF  (12)

/*
 * Hangul decomposition (algorithm from Section 3.12 of Unicode 6.3.0)
 *
 * AC00;<Hangul Syllable, First>;Lo;0;L;;;;;N;;;;;
 * D7A3;<Hangul Syllable, Last>;Lo;0;L;;;;;N;;;;;
 *
 * SBase = 0xAC00
 * LBase = 0x1100
 * VBase = 0x1161
 * TBase = 0x11A7
 * LCount = 19
 * VCount = 21
 * TCount = 28
 * NCount = 588 (VCount * TCount)
 * SCount = 11172 (LCount * NCount)
 *
 * Decomposition:
 *   SIndex = s - SBase
 *
 * LV (Canonical/Full)
 *   LIndex = SIndex / NCount
 *   VIndex = (Sindex % NCount) / TCount
 *   LPart = LBase + LIndex
 *   VPart = VBase + VIndex
 *
 * LVT (Canonical)
 *   LVIndex = (SIndex / TCount) * TCount
 *   TIndex = (Sindex % TCount)
 *   LVPart = SBase + LVIndex
 *   TPart = TBase + TIndex
 *
 * LVT (Full)
 *   LIndex = SIndex / NCount
 *   VIndex = (Sindex % NCount) / TCount
 *   TIndex = (Sindex % TCount)
 *   LPart = LBase + LIndex
 *   VPart = VBase + VIndex
 *   if (TIndex == 0) {
 *          d = <LPart, VPart>
 *   } else {
 *          TPart = TBase + TIndex
 *          d = <LPart, TPart, VPart>
 *   }
 */

/* Constants */
#define SB      (0xAC00)
#define LB      (0x1100)
#define VB      (0x1161)
#define TB      (0x11A7)
#define LC      (19)
#define VC      (21)
#define TC      (28)
#define NC      (VC * TC)
#define SC      (LC * NC)

/* Algorithmic decomposition of hangul syllable. */
static utf8leaf_t *
utf8hangul(const char *str, unsigned char *hangul)
{
        unsigned int    si;
        unsigned int    li;
        unsigned int    vi;
        unsigned int    ti;
        unsigned char   *h;

        /* Calculate the SI, LI, VI, and TI values. */
        si = utf8decode3(str) - SB;
        li = si / NC;
        vi = (si % NC) / TC;
        ti = si % TC;

        /* Fill in base of leaf. */
        h = hangul;
        LEAF_GEN(h) = 2;
        LEAF_CCC(h) = DECOMPOSE;
        h += 2;

        /* Add LPart, a 3-byte UTF-8 sequence. */
        h += utf8encode3((char *)h, li + LB);

        /* Add VPart, a 3-byte UTF-8 sequence. */
        h += utf8encode3((char *)h, vi + VB);

        /* Add TPart if required, also a 3-byte UTF-8 sequence. */
        if (ti)
                h += utf8encode3((char *)h, ti + TB);

        /* Terminate string. */
        h[0] = '\0';

        return hangul;
}

/*
 * Use trie to scan s, touching at most len bytes.
 * Returns the leaf if one exists, NULL otherwise.
 *
 * A non-NULL return guarantees that the UTF-8 sequence starting at s
 * is well-formed and corresponds to a known unicode code point.  The
 * shorthand for this will be "is valid UTF-8 unicode".
 */
static utf8leaf_t *utf8nlookup(const struct utf8data *data,
                               unsigned char *hangul, const char *s, size_t len)
{
        utf8trie_t      *trie;
        int             offlen;
        int             offset;
        int             mask;
        int             node;

        if (!data)
                return NULL;
        if (len == 0)
                return NULL;

        trie = utf8data + data->offset;
        node = 1;
        while (node) {
                offlen = (*trie & OFFLEN) >> OFFLEN_SHIFT;
                if (*trie & NEXTBYTE) {
                        if (--len == 0)
                                return NULL;
                        s++;
                }
                mask = 1 << (*trie & BITNUM);
                if (*s & mask) {
                        /* Right leg */
                        if (offlen) {
                                /* Right node at offset of trie */
                                node = (*trie & RIGHTNODE);
                                offset = trie[offlen];
                                while (--offlen) {
                                        offset <<= 8;
                                        offset |= trie[offlen];
                                }
                                trie += offset;
                        } else if (*trie & RIGHTPATH) {
                                /* Right node after this node */
                                node = (*trie & TRIENODE);
                                trie++;
                        } else {
                                /* No right node. */
                                return NULL;
                        }
                } else {
                        /* Left leg */
                        if (offlen) {
                                /* Left node after this node. */
                                node = (*trie & LEFTNODE);
                                trie += offlen + 1;
                        } else if (*trie & RIGHTPATH) {
                                /* No left node. */
                                return NULL;
                        } else {
                                /* Left node after this node */
                                node = (*trie & TRIENODE);
                                trie++;
                        }
                }
        }
        /*
         * Hangul decomposition is done algorithmically. These are the
         * codepoints >= 0xAC00 and <= 0xD7A3. Their UTF-8 encoding is
         * always 3 bytes long, so s has been advanced twice, and the
         * start of the sequence is at s-2.
         */
        if (LEAF_CCC(trie) == DECOMPOSE && LEAF_STR(trie)[0] == HANGUL)
                trie = utf8hangul(s - 2, hangul);
        return trie;
}

/*
 * Use trie to scan s.
 * Returns the leaf if one exists, NULL otherwise.
 *
 * Forwards to utf8nlookup().
 */
static utf8leaf_t *utf8lookup(const struct utf8data *data,
                              unsigned char *hangul, const char *s)
{
        return utf8nlookup(data, hangul, s, (size_t)-1);
}

#if 0
/*
 * Maximum age of any character in s.
 * Return -1 if s is not valid UTF-8 unicode.
 * Return 0 if only non-assigned code points are used.
 */
static int utf8agemax(const struct utf8data *data, const char *s)
{
        utf8leaf_t      *leaf;
        int             age = 0;
        int             leaf_age;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;

        while (*s) {
                leaf = utf8lookup(data, hangul, s);
                if (!leaf)
                        return -1;

                leaf_age = utf8agetab[LEAF_GEN(leaf)];
                if (leaf_age <= data->maxage && leaf_age > age)
                        age = leaf_age;
                s += utf8clen(s);
        }
        return age;
}
#endif

#if 0
/*
 * Minimum age of any character in s.
 * Return -1 if s is not valid UTF-8 unicode.
 * Return 0 if non-assigned code points are used.
 */
static int utf8agemin(const struct utf8data *data, const char *s)
{
        utf8leaf_t      *leaf;
        int             age;
        int             leaf_age;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;
        age = data->maxage;
        while (*s) {
                leaf = utf8lookup(data, hangul, s);
                if (!leaf)
                        return -1;
                leaf_age = utf8agetab[LEAF_GEN(leaf)];
                if (leaf_age <= data->maxage && leaf_age < age)
                        age = leaf_age;
                s += utf8clen(s);
        }
        return age;
}
#endif

#if 0
/*
 * Maximum age of any character in s, touch at most len bytes.
 * Return -1 if s is not valid UTF-8 unicode.
 */
static int utf8nagemax(const struct utf8data *data, const char *s, size_t len)
{
        utf8leaf_t      *leaf;
        int             age = 0;
        int             leaf_age;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;

        while (len && *s) {
                leaf = utf8nlookup(data, hangul, s, len);
                if (!leaf)
                        return -1;
                leaf_age = utf8agetab[LEAF_GEN(leaf)];
                if (leaf_age <= data->maxage && leaf_age > age)
                        age = leaf_age;
                len -= utf8clen(s);
                s += utf8clen(s);
        }
        return age;
}
#endif

#if 0
/*
 * Maximum age of any character in s, touch at most len bytes.
 * Return -1 if s is not valid UTF-8 unicode.
 */
static int utf8nagemin(const struct utf8data *data, const char *s, size_t len)
{
        utf8leaf_t      *leaf;
        int             leaf_age;
        int             age;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;
        age = data->maxage;
        while (len && *s) {
                leaf = utf8nlookup(data, hangul, s, len);
                if (!leaf)
                        return -1;
                leaf_age = utf8agetab[LEAF_GEN(leaf)];
                if (leaf_age <= data->maxage && leaf_age < age)
                        age = leaf_age;
                len -= utf8clen(s);
                s += utf8clen(s);
        }
        return age;
}
#endif

#if 0
/*
 * Length of the normalization of s.
 * Return -1 if s is not valid UTF-8 unicode.
 *
 * A string of Default_Ignorable_Code_Point has length 0.
 */
static ssize_t utf8len(const struct utf8data *data, const char *s)
{
        utf8leaf_t      *leaf;
        size_t          ret = 0;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;
        while (*s) {
                leaf = utf8lookup(data, hangul, s);
                if (!leaf)
                        return -1;
                if (utf8agetab[LEAF_GEN(leaf)] > data->maxage)
                        ret += utf8clen(s);
                else if (LEAF_CCC(leaf) == DECOMPOSE)
                        ret += strlen(LEAF_STR(leaf));
                else
                        ret += utf8clen(s);
                s += utf8clen(s);
        }
        return ret;
}
#endif

#if 0
/*
 * Length of the normalization of s, touch at most len bytes.
 * Return -1 if s is not valid UTF-8 unicode.
 */
static ssize_t utf8nlen(const struct utf8data *data, const char *s, size_t len)
{
        utf8leaf_t      *leaf;
        size_t          ret = 0;
        unsigned char   hangul[UTF8HANGULLEAF];

        if (!data)
                return -1;
        while (len && *s) {
                leaf = utf8nlookup(data, hangul, s, len);
                if (!leaf)
                        return -1;
                if (utf8agetab[LEAF_GEN(leaf)] > data->maxage)
                        ret += utf8clen(s);
                else if (LEAF_CCC(leaf) == DECOMPOSE)
                        ret += strlen(LEAF_STR(leaf));
                else
                        ret += utf8clen(s);
                len -= utf8clen(s);
                s += utf8clen(s);
        }
        return ret;
}
#endif

/*
 * Set up an utf8cursor for use by utf8byte().
 *
 *   u8c    : pointer to cursor.
 *   data   : const struct utf8data to use for normalization.
 *   s      : string.
 *   len    : length of s.
 *
 * Returns -1 on error, 0 on success.
 */
static int utf8ncursor(struct utf8cursor *u8c, const struct utf8data *data,
                const char *s, size_t len)
{
        if (!data)
                return -1;
        if (!s)
                return -1;
        u8c->data = data;
        u8c->s = s;
        u8c->p = NULL;
        u8c->ss = NULL;
        u8c->sp = NULL;
        u8c->len = len;
        u8c->slen = 0;
        u8c->ccc = STOPPER;
        u8c->nccc = STOPPER;
        /* Check we didn't clobber the maximum length. */
        if (u8c->len != len)
                return -1;
        /* The first byte of s may not be an utf8 continuation. */
        if (len > 0 && (*s & 0xC0) == 0x80)
                return -1;
        return 0;
}

#if 0
/*
 * Set up an utf8cursor for use by utf8byte().
 *
 *   u8c    : pointer to cursor.
 *   data   : const struct utf8data to use for normalization.
 *   s      : NUL-terminated string.
 *
 * Returns -1 on error, 0 on success.
 */
static int utf8cursor(struct utf8cursor *u8c, const struct utf8data *data,
               const char *s)
{
        return utf8ncursor(u8c, data, s, (unsigned int)-1);
}
#endif

/*
 * Get one byte from the normalized form of the string described by u8c.
 *
 * Returns the byte cast to an unsigned char on succes, and -1 on failure.
 *
 * The cursor keeps track of the location in the string in u8c->s.
 * When a character is decomposed, the current location is stored in
 * u8c->p, and u8c->s is set to the start of the decomposition. Note
 * that bytes from a decomposition do not count against u8c->len.
 *
 * Characters are emitted if they match the current CCC in u8c->ccc.
 * Hitting end-of-string while u8c->ccc == STOPPER means we're done,
 * and the function returns 0 in that case.
 *
 * Sorting by CCC is done by repeatedly scanning the string.  The
 * values of u8c->s and u8c->p are stored in u8c->ss and u8c->sp at
 * the start of the scan.  The first pass finds the lowest CCC to be
 * emitted and stores it in u8c->nccc, the second pass emits the
 * characters with this CCC and finds the next lowest CCC. This limits
 * the number of passes to 1 + the number of different CCCs in the
 * sequence being scanned.
 *
 * Therefore:
 *  u8c->p  != NULL -> a decomposition is being scanned.
 *  u8c->ss != NULL -> this is a repeating scan.
 *  u8c->ccc == -1   -> this is the first scan of a repeating scan.
 */
static int utf8byte(struct utf8cursor *u8c)
{
        utf8leaf_t *leaf;
        int ccc;

        for (;;) {
                /* Check for the end of a decomposed character. */
                if (u8c->p && *u8c->s == '\0') {
                        u8c->s = u8c->p;
                        u8c->p = NULL;
                }

                /* Check for end-of-string. */
                if (!u8c->p && (u8c->len == 0 || *u8c->s == '\0')) {
                        /* There is no next byte. */
                        if (u8c->ccc == STOPPER)
                                return 0;
                        /* End-of-string during a scan counts as a stopper. */
                        ccc = STOPPER;
                        goto ccc_mismatch;
                } else if ((*u8c->s & 0xC0) == 0x80) {
                        /* This is a continuation of the current character. */
                        if (!u8c->p)
                                u8c->len--;
                        return (unsigned char)*u8c->s++;
                }

                /* Look up the data for the current character. */
                if (u8c->p) {
                        leaf = utf8lookup(u8c->data, u8c->hangul, u8c->s);
                } else {
                        leaf = utf8nlookup(u8c->data, u8c->hangul,
                                           u8c->s, u8c->len);
                }

                /* No leaf found implies that the input is a binary blob. */
                if (!leaf)
                        return -1;

                ccc = LEAF_CCC(leaf);
                /* Characters that are too new have CCC 0. */
                if (utf8agetab[LEAF_GEN(leaf)] > u8c->data->maxage) {
                        ccc = STOPPER;
                } else if (ccc == DECOMPOSE) {
                        u8c->len -= utf8clen(u8c->s);
                        u8c->p = u8c->s + utf8clen(u8c->s);
                        u8c->s = LEAF_STR(leaf);
                        /* Empty decomposition implies CCC 0. */
                        if (*u8c->s == '\0') {
                                if (u8c->ccc == STOPPER)
                                        continue;
                                ccc = STOPPER;
                                goto ccc_mismatch;
                        }

                        leaf = utf8lookup(u8c->data, u8c->hangul, u8c->s);
                        ccc = LEAF_CCC(leaf);
                }

                /*
                 * If this is not a stopper, then see if it updates
                 * the next canonical class to be emitted.
                 */
                if (ccc != STOPPER && u8c->ccc < ccc && ccc < u8c->nccc)
                        u8c->nccc = ccc;

                /*
                 * Return the current byte if this is the current
                 * combining class.
                 */
                if (ccc == u8c->ccc) {
                        if (!u8c->p)
                                u8c->len--;
                        return (unsigned char)*u8c->s++;
                }

                /* Current combining class mismatch. */
ccc_mismatch:
                if (u8c->nccc == STOPPER) {
                        /*
                         * Scan forward for the first canonical class
                         * to be emitted.  Save the position from
                         * which to restart.
                         */
                        u8c->ccc = MINCCC - 1;
                        u8c->nccc = ccc;
                        u8c->sp = u8c->p;
                        u8c->ss = u8c->s;
                        u8c->slen = u8c->len;
                        if (!u8c->p)
                                u8c->len -= utf8clen(u8c->s);
                        u8c->s += utf8clen(u8c->s);
                } else if (ccc != STOPPER) {
                        /* Not a stopper, and not the ccc we're emitting. */
                        if (!u8c->p)
                                u8c->len -= utf8clen(u8c->s);
                        u8c->s += utf8clen(u8c->s);
                } else if (u8c->nccc != MAXCCC + 1) {
                        /* At a stopper, restart for next ccc. */
                        u8c->ccc = u8c->nccc;
                        u8c->nccc = MAXCCC + 1;
                        u8c->s = u8c->ss;
                        u8c->p = u8c->sp;
                        u8c->len = u8c->slen;
                } else {
                        /* All done, proceed from here. */
                        u8c->ccc = STOPPER;
                        u8c->nccc = STOPPER;
                        u8c->sp = NULL;
                        u8c->ss = NULL;
                        u8c->slen = 0;
                }
        }
}

#if 0
/*
 * Look for the correct const struct utf8data for a unicode version.
 * Returns NULL if the version requested is too new.
 *
 * Two normalization forms are supported: nfdi and nfdicf.
 *
 * nfdi:
 *  - Apply unicode normalization form NFD.
 *  - Remove any Default_Ignorable_Code_Point.
 *
 * nfdicf:
 *  - Apply unicode normalization form NFD.
 *  - Remove any Default_Ignorable_Code_Point.
 *  - Apply a full casefold (C + F).
 */
static const struct utf8data *utf8nfdi(unsigned int maxage)
{
        int i = ARRAY_SIZE(utf8nfdidata) - 1;

        while (maxage < utf8nfdidata[i].maxage)
                i--;
        if (maxage > utf8nfdidata[i].maxage)
                return NULL;
        return &utf8nfdidata[i];
}
#endif

static const struct utf8data *utf8nfdicf(unsigned int maxage)
{
        int i = ARRAY_SIZE(utf8nfdicfdata) - 1;

        while (maxage < utf8nfdicfdata[i].maxage)
                i--;
        if (maxage > utf8nfdicfdata[i].maxage)
                return NULL;
        return &utf8nfdicfdata[i];
}

static int utf8_casefold(const struct ext2fs_nls_table *table,
                          const unsigned char *str, size_t len,
                          unsigned char *dest, size_t dlen)
{
        const struct utf8data *data = utf8nfdicf(table->version);
        struct utf8cursor cur;
        size_t nlen = 0;

        if (utf8ncursor(&cur, data, (const char *) str, len) < 0)
                goto invalid_seq;

        for (nlen = 0; nlen < dlen; nlen++) {
                int c = utf8byte(&cur);

                dest[nlen] = c;
                if (!c)
                        return nlen;
                if (c == -1)
                        break;
        }

        return -ENAMETOOLONG;

invalid_seq:
        if (dlen < len)
                return -ENAMETOOLONG;

        /* Signal invalid sequence */
        return -EINVAL;
}

static const struct ext2fs_nls_ops utf8_ops = {
        .casefold = utf8_casefold,
};

static const struct ext2fs_nls_table nls_utf8 = {
        .ops = &utf8_ops,
        .version = UNICODE_AGE(12, 1, 0),
};

const struct ext2fs_nls_table *ext2fs_load_nls_table(int encoding)
{
        if (encoding == EXT4_ENC_UTF8_12_1)
                return &nls_utf8;

        return NULL;
}