/*-
 * Copyright (c) 2002-2004 Tim J. Robbins
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
__FBSDID("$FreeBSD$");

#include <errno.h>
#include <runetype.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>

extern size_t (*__mbrtowc)(wchar_t * __restrict, const char * __restrict,
    size_t, mbstate_t * __restrict);
extern int (*__mbsinit)(const mbstate_t *);
extern size_t (*__wcrtomb)(char * __restrict, wchar_t, mbstate_t * __restrict);

size_t	_UTF8_mbrtowc(wchar_t * __restrict, const char * __restrict, size_t,
	    mbstate_t * __restrict);
int	_UTF8_mbsinit(const mbstate_t *);
size_t	_UTF8_wcrtomb(char * __restrict, wchar_t, mbstate_t * __restrict);

typedef struct {
	int	count;
	u_char	bytes[6];
} _UTF8State;

int
_UTF8_init(_RuneLocale *rl)
{

	__mbrtowc = _UTF8_mbrtowc;
	__wcrtomb = _UTF8_wcrtomb;
	__mbsinit = _UTF8_mbsinit;
	_CurrentRuneLocale = rl;
	__mb_cur_max = 6;

	return (0);
}

int
_UTF8_mbsinit(const mbstate_t *ps)
{

	return (ps == NULL || ((const _UTF8State *)ps)->count == 0);
}

size_t
_UTF8_mbrtowc(wchar_t * __restrict pwc, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps)
{
	_UTF8State *us;
	int ch, i, len, mask, ocount;
	wchar_t lbound, wch;
	size_t ncopy;

	us = (_UTF8State *)ps;

	if (us->count < 0 || us->count > sizeof(us->bytes)) {
		errno = EINVAL;
		return ((size_t)-1);
	}

	if (s == NULL) {
		s = "";
		n = 1;
		pwc = NULL;
	}

	ncopy = MIN(MIN(n, MB_CUR_MAX), sizeof(us->bytes) - us->count);
	memcpy(us->bytes + us->count, s, ncopy);
	ocount = us->count;
	us->count += ncopy;
	s = (char *)us->bytes;
	n = us->count;

	if (n == 0)
		/* Incomplete multibyte sequence */
		return ((size_t)-2);

	/*
	 * Determine the number of octets that make up this character from
	 * the first octet, and a mask that extracts the interesting bits of
	 * the first octet.
	 *
	 * We also specify a lower bound for the character code to detect
	 * redundant, non-"shortest form" encodings. For example, the
	 * sequence C0 80 is _not_ a legal representation of the null
	 * character. This enforces a 1-to-1 mapping between character
	 * codes and their multibyte representations.
	 */
	ch = (unsigned char)*s;
	if ((ch & 0x80) == 0) {
		mask = 0x7f;
		len = 1;
		lbound = 0;
	} else if ((ch & 0xe0) == 0xc0) {
		mask = 0x1f;
		len = 2;
		lbound = 0x80;
	} else if ((ch & 0xf0) == 0xe0) {
		mask = 0x0f;
		len = 3;
		lbound = 0x800;
	} else if ((ch & 0xf8) == 0xf0) {
		mask = 0x07;
		len = 4;
		lbound = 0x10000;
	} else if ((ch & 0xfc) == 0xf8) {
		mask = 0x03;
		len = 5;
		lbound = 0x200000;
	} else if ((ch & 0xfc) == 0xfc) {
		mask = 0x01;
		len = 6;
		lbound = 0x4000000;
	} else {
		/*
		 * Malformed input; input is not UTF-8.
		 */
		errno = EILSEQ;
		return ((size_t)-1);
	}

	if (n < (size_t)len)
		/* Incomplete multibyte sequence */
		return ((size_t)-2);

	/*
	 * Decode the octet sequence representing the character in chunks
	 * of 6 bits, most significant first.
	 */
	wch = (unsigned char)*s++ & mask;
	i = len;
	while (--i != 0) {
		if ((*s & 0xc0) != 0x80) {
			/*
			 * Malformed input; bad characters in the middle
			 * of a character.
			 */
			errno = EILSEQ;
			return ((size_t)-1);
		}
		wch <<= 6;
		wch |= *s++ & 0x3f;
	}
	if (wch < lbound) {
		/*
		 * Malformed input; redundant encoding.
		 */
		errno = EILSEQ;
		return ((size_t)-1);
	}
	if (pwc != NULL)
		*pwc = wch;
	us->count = 0;
	return (wch == L'\0' ? 0 : len - ocount);
}

size_t
_UTF8_wcrtomb(char * __restrict s, wchar_t wc, mbstate_t * __restrict ps)
{
	_UTF8State *us;
	unsigned char lead;
	int i, len;

	us = (_UTF8State *)ps;

	if (us->count < 0 || us->count > sizeof(us->bytes)) {
		errno = EINVAL;
		return ((size_t)-1);
	}

	if (s == NULL)
		/* Reset to initial shift state (no-op) */
		return (1);

	/*
	 * Determine the number of octets needed to represent this character.
	 * We always output the shortest sequence possible. Also specify the
	 * first few bits of the first octet, which contains the information
	 * about the sequence length.
	 */
	if ((wc & ~0x7f) == 0) {
		lead = 0;
		len = 1;
	} else if ((wc & ~0x7ff) == 0) {
		lead = 0xc0;
		len = 2;
	} else if ((wc & ~0xffff) == 0) {
		lead = 0xe0;
		len = 3;
	} else if ((wc & ~0x1fffff) == 0) {
		lead = 0xf0;
		len = 4;
	} else if ((wc & ~0x3ffffff) == 0) {
		lead = 0xf8;
		len = 5;
	} else if ((wc & ~0x7fffffff) == 0) {
		lead = 0xfc;
		len = 6;
	} else {
		errno = EILSEQ;
		return ((size_t)-1);
	}

	/*
	 * Output the octets representing the character in chunks
	 * of 6 bits, least significant last. The first octet is
	 * a special case because it contains the sequence length
	 * information.
	 */
	for (i = len - 1; i > 0; i--) {
		s[i] = (wc & 0x3f) | 0x80;
		wc >>= 6;
	}
	*s = (wc & 0xff) | lead;

	return (len);
}