/*	$OpenBSD: citrus_utf8.c,v 1.18 2016/09/07 17:15:06 schwarze Exp $ */

/*-
 * 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/types.h>

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

#include "citrus_ctype.h"

struct _utf8_state {
	wchar_t	ch;
	int	want;
	wchar_t	lbound;
};

size_t
_citrus_utf8_ctype_mbrtowc(wchar_t * __restrict pwc,
    const char * __restrict s, size_t n, mbstate_t * __restrict ps)
{
	struct _utf8_state *us;
	int ch, i, mask, want;
	wchar_t lbound, wch;

	us = (struct _utf8_state *)ps;

	if (us->want < 0 || us->want > _CITRUS_UTF8_MB_CUR_MAX) {
		errno = EINVAL;
		return -1;
	}

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

	if (n == 0)
		return -2;

	if (us->want == 0 && ((ch = (unsigned char)*s) & ~0x7f) == 0) {
		/* Fast path for plain ASCII characters. */
		if (pwc != NULL)
			*pwc = ch;
		return ch != '\0' ? 1 : 0;
	}

	if (us->want == 0) {
		/*
		 * Determine the number of bytes that make up this character
		 * from the first byte, and a mask that extracts the
		 * interesting bits of the first byte.  We already know
		 * the character is at least two bytes long.
		 *
		 * 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;
			want = 1;
			lbound = 0;
		} else if ((ch & 0xe0) == 0xc0) {
			mask = 0x1f;
			want = 2;
			lbound = 0x80;
		} else if ((ch & 0xf0) == 0xe0) {
			mask = 0x0f;
			want = 3;
			lbound = 0x800;
		} else if ((ch & 0xf8) == 0xf0) {
			mask = 0x07;
			want = 4;
			lbound = 0x10000;
		} else {
			/*
			 * Malformed input; input is not UTF-8.
			 * See RFC 3629.
			 */
			errno = EILSEQ;
			return -1;
		}
	} else {
		want = us->want;
		lbound = us->lbound;
	}

	/*
	 * Decode the byte sequence representing the character in chunks
	 * of 6 bits, most significant first.
	 */
	if (us->want == 0)
		wch = (unsigned char)*s++ & mask;
	else
		wch = us->ch;
	for (i = (us->want == 0) ? 1 : 0; i < want && (size_t)i < n; i++) {
		if ((*s & 0xc0) != 0x80) {
			/*
			 * Malformed input; bad byte in the middle
			 * of a character.
			 */
			errno = EILSEQ;
			return -1;
		}
		wch <<= 6;
		wch |= *s++ & 0x3f;
	}
	if (i < want) {
		/* Incomplete multibyte sequence. */
		us->want = want - i;
		us->lbound = lbound;
		us->ch = wch;
		return -2;
	}
	if (wch < lbound) {
		/*
		 * Malformed input; redundant encoding.
		 */
		errno = EILSEQ;
		return -1;
	}
	if (wch >= 0xd800 && wch <= 0xdfff) {
		/*
		 * Malformed input; invalid code points.
		 */
		errno = EILSEQ;
		return -1;
	}
	if (wch > 0x10ffff) {
		/*
		 * Malformed input; invalid code points.
		 */
		errno = EILSEQ;
		return -1;
	}
	if (pwc != NULL)
		*pwc = wch;
	us->want = 0;
	return wch == L'\0' ? 0 : want;
}

int
_citrus_utf8_ctype_mbsinit(const mbstate_t * __restrict ps)
{
	return ((const struct _utf8_state *)ps)->want == 0;
}

size_t
_citrus_utf8_ctype_mbsnrtowcs(wchar_t * __restrict dst,
    const char ** __restrict src, size_t nmc, size_t len,
    mbstate_t * __restrict ps)
{
	struct _utf8_state *us;
	size_t i, o, r;

	us = (struct _utf8_state *)ps;

	if (dst == NULL) {
		/*
		 * The fast path in the loop below is not safe if an ASCII
		 * character appears as anything but the first byte of a
		 * multibyte sequence. Check now to avoid doing it in the loop.
		 */
		if (nmc > 0 && us->want > 0 && (unsigned char)(*src)[0] < 0x80) {
			errno = EILSEQ;
			return -1;
		}
		for (i = o = 0; i < nmc; i += r, o++) {
			if ((unsigned char)(*src)[i] < 0x80) {
				/* Fast path for plain ASCII characters. */
				if ((*src)[i] == '\0')
					return o;
				r = 1;
			} else {
				r = _citrus_utf8_ctype_mbrtowc(NULL, *src + i,
				    nmc - i, ps);
				if (r == (size_t)-1)
					return r;
				if (r == (size_t)-2)
					return o;
				if (r == 0)
					return o;
			}
		}
		return o;
	}

	/*
	 * The fast path in the loop below is not safe if an ASCII
	 * character appears as anything but the first byte of a
	 * multibyte sequence. Check now to avoid doing it in the loop.
	 */
	if (len > 0 && nmc > 0 && us->want > 0 &&
	    (unsigned char)(*src)[0] < 0x80) {
		errno = EILSEQ;
		return -1;
	}
	for (i = o = 0; i < nmc && o < len; i += r, o++) {
		if ((unsigned char)(*src)[i] < 0x80) {
			/* Fast path for plain ASCII characters. */
			dst[o] = (wchar_t)(unsigned char)(*src)[i];
			if ((*src)[i] == '\0') {
				*src = NULL;
				return o;
			}
			r = 1;
		} else {
			r = _citrus_utf8_ctype_mbrtowc(dst + o, *src + i,
			    nmc - i, ps);
			if (r == (size_t)-1) {
				*src += i;
				return r;
			}
			if (r == (size_t)-2) {
				*src += nmc;
				return o;
			}
			if (r == 0) {
				*src = NULL;
				return o;
			}
		}
	}
	*src += i;
	return o;
}

size_t
_citrus_utf8_ctype_wcrtomb(char * __restrict s, wchar_t wc,
    mbstate_t * __restrict ps)
{
	struct _utf8_state *us;
	unsigned char lead;
	int i, len;

	us = (struct _utf8_state *)ps;

	if (us->want != 0) {
		errno = EINVAL;
		return -1;
	}

	if (s == NULL)
		return 1;

	if (wc < 0 || (wc > 0xd7ff && wc < 0xe000) || wc > 0x10ffff) {
		errno = EILSEQ;
		return -1;
	}

	/*
	 * Determine the number of bytes needed to represent this character.
	 * We always output the shortest sequence possible. Also specify the
	 * first few bits of the first byte, which contains the information
	 * about the sequence length.
	 */
	if (wc <= 0x7f) {
		/* Fast path for plain ASCII characters. */
		*s = (char)wc;
		return 1;
	} else if (wc <= 0x7ff) {
		lead = 0xc0;
		len = 2;
	} else if (wc <= 0xffff) {
		lead = 0xe0;
		len = 3;
	} else {
		lead = 0xf0;
		len = 4;
	}

	/*
	 * Output the bytes representing the character in chunks
	 * of 6 bits, least significant last. The first byte 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;
}

size_t
_citrus_utf8_ctype_wcsnrtombs(char * __restrict dst,
    const wchar_t ** __restrict src, size_t nwc, size_t len,
    mbstate_t * __restrict ps)
{
	struct _utf8_state *us;
	char buf[_CITRUS_UTF8_MB_CUR_MAX];
	size_t i, o, r;

	us = (struct _utf8_state *)ps;

	if (us->want != 0) {
		errno = EINVAL;
		return -1;
	}

	if (dst == NULL) {
		for (i = o = 0; i < nwc; i++, o += r) {
			wchar_t wc = (*src)[i];
			if (wc >= 0 && wc < 0x80) {
				/* Fast path for plain ASCII characters. */
				if (wc == 0)
					return o;
				r = 1;
			} else {
				r = _citrus_utf8_ctype_wcrtomb(buf, wc, ps);
				if (r == (size_t)-1)
					return r;
			}
		}
		return o;
	}

	for (i = o = 0; i < nwc && o < len; i++, o += r) {
		wchar_t wc = (*src)[i];
		if (wc >= 0 && wc < 0x80) {
			/* Fast path for plain ASCII characters. */
			dst[o] = (wchar_t)wc;
			if (wc == 0) {
				*src = NULL;
				return o;
			}
			r = 1;
		} else if (len - o >= _CITRUS_UTF8_MB_CUR_MAX) {
			/* Enough space to translate in-place. */
			r = _citrus_utf8_ctype_wcrtomb(dst + o, wc, ps);
			if (r == (size_t)-1) {
				*src += i;
				return r;
			}
		} else {
			/* May not be enough space; use temp buffer. */
			r = _citrus_utf8_ctype_wcrtomb(buf, wc, ps);
			if (r == (size_t)-1) {
				*src += i;
				return r;
			}
			if (r > len - o)
				break;
			memcpy(dst + o, buf, r);
		}
	}
	*src += i;
	return o;
}