/*

 * 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);

			if (!leaf)

				return -1;

			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