/*      $NetBSD: citrus_utf1632.c,v 1.13 2022/04/19 20:32:14 rillig Exp $       */

/*-
 * Copyright (c)2003 Citrus Project,
 * 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/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: citrus_utf1632.c,v 1.13 2022/04/19 20:32:14 rillig Exp $");
#endif /* LIBC_SCCS and not lint */

#include <assert.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <limits.h>
#include <wchar.h>
#include <sys/types.h>
#include <machine/endian.h>

#include "citrus_namespace.h"
#include "citrus_types.h"
#include "citrus_module.h"
#include "citrus_stdenc.h"
#include "citrus_bcs.h"

#include "citrus_utf1632.h"


/* ----------------------------------------------------------------------
 * private stuffs used by templates
 */

typedef struct {
        u_int8_t                ch[4];
        int                     chlen;
        int                     current_endian;
} _UTF1632State;

typedef struct {
        int             preffered_endian;
        unsigned int    cur_max;
#define _ENDIAN_UNKNOWN 0
#define _ENDIAN_BIG     1
#define _ENDIAN_LITTLE  2
        u_int32_t       mode;
#define _MODE_UTF32             0x00000001U
#define _MODE_FORCE_ENDIAN      0x00000002U
} _UTF1632EncodingInfo;

#define _FUNCNAME(m)                    _citrus_UTF1632_##m
#define _ENCODING_INFO                  _UTF1632EncodingInfo
#define _ENCODING_STATE                 _UTF1632State
#define _ENCODING_MB_CUR_MAX(_ei_)      ((_ei_)->cur_max)
#define _ENCODING_IS_STATE_DEPENDENT    0
#define _STATE_NEEDS_EXPLICIT_INIT(_ps_)        0


static __inline void
/*ARGSUSED*/
_citrus_UTF1632_init_state(_UTF1632EncodingInfo *ei, _UTF1632State *s)
{
        memset(s, 0, sizeof(*s));
}

static int
_citrus_UTF1632_mbrtowc_priv(_UTF1632EncodingInfo *ei, wchar_t *pwc,
                             const char **s, size_t n, _UTF1632State *psenc,
                             size_t *nresult)
{
        int chlenbak, endian, needlen;
        wchar_t wc;
        size_t result;
        const char *s0;

        _DIAGASSERT(nresult != 0);
        _DIAGASSERT(ei != NULL);
        _DIAGASSERT(s != NULL);
        _DIAGASSERT(psenc != NULL);

        s0 = *s;

        if (s0 == NULL) {
                _citrus_UTF1632_init_state(ei, psenc);
                *nresult = 0; /* state independent */
                return (0);
        }

        result = 0;
        chlenbak = psenc->chlen;

refetch:
        if ((ei->mode & _MODE_UTF32) != 0 || chlenbak>=2)
                needlen = 4;
        else
                needlen = 2;

        while (chlenbak < needlen) {
                if (n==0)
                        goto restart;
                psenc->ch[chlenbak++] = *s0++;
                n--;
                result++;
        }

        if (psenc->current_endian == _ENDIAN_UNKNOWN) {
                if ((ei->mode & _MODE_FORCE_ENDIAN) == 0) {
                        /* judge endian marker */
                        if ((ei->mode & _MODE_UTF32) == 0) {
                                /* UTF16 */
                                if (psenc->ch[0]==0xFE && psenc->ch[1]==0xFF) {
                                        psenc->current_endian = _ENDIAN_BIG;
                                        chlenbak = 0;
                                        goto refetch;
                                } else if (psenc->ch[0]==0xFF && psenc->ch[1]==0xFE) {
                                        psenc->current_endian = _ENDIAN_LITTLE;
                                        chlenbak = 0;
                                        goto refetch;
                                }
                        } else {
                                /* UTF32 */
                                if (psenc->ch[0]==0x00 && psenc->ch[1]==0x00 &&
                                    psenc->ch[2]==0xFE && psenc->ch[3]==0xFF) {
                                        psenc->current_endian = _ENDIAN_BIG;
                                        chlenbak = 0;
                                        goto refetch;
                                } else if (psenc->ch[0]==0xFF && psenc->ch[1]==0xFE &&
                                           psenc->ch[2]==0x00 && psenc->ch[3]==0x00) {
                                        psenc->current_endian = _ENDIAN_LITTLE;
                                        chlenbak = 0;
                                        goto refetch;
                                }
                        }
                }
                psenc->current_endian = ei->preffered_endian;
        }
        endian = psenc->current_endian;

        /* get wc */
        if ((ei->mode & _MODE_UTF32) == 0) {
                /* UTF16 */
                if (needlen==2) {
                        switch (endian) {
                        case _ENDIAN_LITTLE:
                                wc = (psenc->ch[0] |
                                      ((wchar_t)psenc->ch[1] << 8));
                                break;
                        case _ENDIAN_BIG:
                                wc = (psenc->ch[1] |
                                      ((wchar_t)psenc->ch[0] << 8));
                                break;
                        default:
                                goto ilseq;
                        }
                        if (wc >= 0xD800 && wc <= 0xDBFF) {
                                /* surrogate high */
                                needlen=4;
                                goto refetch;
                        }
                } else {
                        /* surrogate low */
                        wc -= 0xD800; /* wc : surrogate high (see above) */
                        wc <<= 10;
                        switch (endian) {
                        case _ENDIAN_LITTLE:
                                if (psenc->ch[3]<0xDC || psenc->ch[3]>0xDF)
                                        goto ilseq;
                                wc |= psenc->ch[2];
                                wc |= (wchar_t)(psenc->ch[3] & 3) << 8;
                                break;
                        case _ENDIAN_BIG:
                                if (psenc->ch[2]<0xDC || psenc->ch[2]>0xDF)
                                        goto ilseq;
                                wc |= psenc->ch[3];
                                wc |= (wchar_t)(psenc->ch[2] & 3) << 8;
                                break;
                        default:
                                goto ilseq;
                        }
                        wc += 0x10000;
                }
        } else {
                /* UTF32 */
                switch (endian) {
                case _ENDIAN_LITTLE:
                        wc = (psenc->ch[0] |
                              ((wchar_t)psenc->ch[1] << 8) |
                              ((wchar_t)psenc->ch[2] << 16) |
                              ((wchar_t)psenc->ch[3] << 24));
                        break;
                case _ENDIAN_BIG:
                        wc = (psenc->ch[3] |
                              ((wchar_t)psenc->ch[2] << 8) |
                              ((wchar_t)psenc->ch[1] << 16) |
                              ((wchar_t)psenc->ch[0] << 24));
                        break;
                default:
                        goto ilseq;
                }
                if (wc >= 0xD800 && wc <= 0xDFFF)
                        goto ilseq;
        }


        *pwc = wc;
        psenc->chlen = 0;
        *nresult = result;
        *s = s0;

        return (0);

ilseq:
        *nresult = (size_t)-1;
        psenc->chlen = 0;
        return (EILSEQ);

restart:
        *nresult = (size_t)-2;
        psenc->chlen = chlenbak;
        *s = s0;
        return (0);
}

static int
_citrus_UTF1632_wcrtomb_priv(_UTF1632EncodingInfo *ei, char *s, size_t n,
                             wchar_t wc, _UTF1632State *psenc,
                             size_t *nresult)
{
        wchar_t wc2;
        static const char _bom[4] = {
#if BYTE_ORDER == BIG_ENDIAN
            0x00, 0x00, 0xFE, 0xFF,
#else
            0xFF, 0xFE, 0x00, 0x00,
#endif
        };
        const char *bom = &_bom[0];
        size_t cnt;

        _DIAGASSERT(ei != NULL);
        _DIAGASSERT(nresult != 0);
        _DIAGASSERT(s != NULL);

        cnt = (size_t)0;
        if (psenc->current_endian == _ENDIAN_UNKNOWN) {
                if ((ei->mode & _MODE_FORCE_ENDIAN) == 0) {
                        if (ei->mode & _MODE_UTF32) {
                                cnt = 4;
                        } else {
                                cnt = 2;
#if BYTE_ORDER == BIG_ENDIAN
                                bom += 2;
#endif
                        }
                        if (n < cnt)
                                goto e2big;
                        memcpy(s, bom, cnt);
                        s += cnt, n -= cnt;
                }
                psenc->current_endian = ei->preffered_endian;
        }

        wc2 = 0;
        if ((ei->mode & _MODE_UTF32)==0) {
                /* UTF16 */
                if (wc>0xFFFF) {
                        /* surrogate */
                        if (wc>0x10FFFF)
                                goto ilseq;
                        if (n < 4)
                                goto e2big;
                        cnt += 4;
                        wc -= 0x10000;
                        wc2 = (wc & 0x3FF) | 0xDC00;
                        wc = (wc>>10) | 0xD800;
                } else {
                        if (n < 2)
                                goto e2big;
                        cnt += 2;
                }

surrogate:
                switch (psenc->current_endian) {
                case _ENDIAN_BIG:
                        s[1] = wc;
                        s[0] = (wc >>= 8);
                        break;
                case _ENDIAN_LITTLE:
                        s[0] = wc;
                        s[1] = (wc >>= 8);
                        break;
                }
                if (wc2!=0) {
                        wc = wc2;
                        wc2 = 0;
                        s += 2;
                        goto surrogate;
                }
        } else {
                /* UTF32 */
                if (wc >= 0xD800 && wc <= 0xDFFF)
                        goto ilseq;
                if (n < 4)
                        goto e2big;
                cnt += 4;
                switch (psenc->current_endian) {
                case _ENDIAN_BIG:
                        s[3] = wc;
                        s[2] = (wc >>= 8);
                        s[1] = (wc >>= 8);
                        s[0] = (wc >>= 8);
                        break;
                case _ENDIAN_LITTLE:
                        s[0] = wc;
                        s[1] = (wc >>= 8);
                        s[2] = (wc >>= 8);
                        s[3] = (wc >>= 8);
                        break;
                }
        }
        *nresult = cnt;

        return 0;

ilseq:
        *nresult = (size_t)-1;
        return EILSEQ;
e2big:
        *nresult = (size_t)-1;
        return E2BIG;
}

static void
parse_variable(_UTF1632EncodingInfo * __restrict ei,
               const void * __restrict var, size_t lenvar)
{
#define MATCH(x, act)                                           \
do {                                                            \
        if (lenvar >= (sizeof(#x)-1) &&                         \
            _bcs_strncasecmp(p, #x, sizeof(#x)-1) == 0) {       \
                act;                                            \
                lenvar -= sizeof(#x)-1;                         \
                p += sizeof(#x)-1;                              \
        }                                                       \
} while (0)
        const char *p;
        p = var;
        while (lenvar>0) {
                switch (*p) {
                case 'B':
                case 'b':
                        MATCH(big, ei->preffered_endian = _ENDIAN_BIG);
                        break;
                case 'L':
                case 'l':
                        MATCH(little, ei->preffered_endian = _ENDIAN_LITTLE);
                        break;
                case 'F':
                case 'f':
                        MATCH(force, ei->mode |= _MODE_FORCE_ENDIAN);
                        break;
                case 'U':
                case 'u':
                        MATCH(utf32, ei->mode |= _MODE_UTF32);
                        break;
                }
                p++;
                lenvar--;
        }
}

static int
/*ARGSUSED*/
_citrus_UTF1632_encoding_module_init(_UTF1632EncodingInfo * __restrict ei,
                                     const void * __restrict var,
                                     size_t lenvar)
{
        _DIAGASSERT(ei != NULL);

        memset((void *)ei, 0, sizeof(*ei));

        parse_variable(ei, var, lenvar);

        if ((ei->mode&_MODE_UTF32)==0)
                ei->cur_max = 6; /* endian + surrogate */
        else
                ei->cur_max = 8; /* endian + normal */

        if (ei->preffered_endian == _ENDIAN_UNKNOWN) {
#if BYTE_ORDER == BIG_ENDIAN
                ei->preffered_endian = _ENDIAN_BIG;
#else
                ei->preffered_endian = _ENDIAN_LITTLE;
#endif
        }

        return (0);
}

static void
/*ARGSUSED*/
_citrus_UTF1632_encoding_module_uninit(_UTF1632EncodingInfo *ei)
{
}

static __inline int
/*ARGSUSED*/
_citrus_UTF1632_stdenc_wctocs(_UTF1632EncodingInfo * __restrict ei,
                              _csid_t * __restrict csid,
                              _index_t * __restrict idx,
                              _wc_t wc)
{

        _DIAGASSERT(csid != NULL && idx != NULL);

        *csid = 0;
        *idx = (_index_t)wc;

        return (0);
}

static __inline int
/*ARGSUSED*/
_citrus_UTF1632_stdenc_cstowc(_UTF1632EncodingInfo * __restrict ei,
                              _wc_t * __restrict wc,
                              _csid_t csid, _index_t idx)
{

        _DIAGASSERT(wc != NULL);

        if (csid != 0)
                return (EILSEQ);

        *wc = (_wc_t)idx;

        return (0);
}

static __inline int
/*ARGSUSED*/
_citrus_UTF1632_stdenc_get_state_desc_generic(_UTF1632EncodingInfo * __restrict ei,
                                              _UTF1632State * __restrict psenc,
                                              int * __restrict rstate)
{

        if (psenc->chlen == 0)
                *rstate = _STDENC_SDGEN_INITIAL;
        else
                *rstate = _STDENC_SDGEN_INCOMPLETE_CHAR;

        return 0;
}

/* ----------------------------------------------------------------------
 * public interface for stdenc
 */

_CITRUS_STDENC_DECLS(UTF1632);
_CITRUS_STDENC_DEF_OPS(UTF1632);

#include "citrus_stdenc_template.h"