/*      $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;
}