/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1995, by Sun Microsystems, Inc.
 * All rights reserved.
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <errno.h>
#include "unicode_cns11643_TW.h"        /* UTF8 to CNS 11643 mapping table */
#include "common_defs.h"

#define MSB     0x80    /* most significant bit */
#define MBYTE   0x8e    /* multi-byte (4 byte character) */
#define PMASK   0xa0    /* plane number mask */
#define ONEBYTE 0xff    /* right most byte */

#define SI      0x0f    /* shift in */
#define SO      0x0e    /* shift out */
#define ESC     0x1b    /* escape */

/* static const char plane_char[] = "0GH23456789:;<=>?"; */
static const char plane_char[] = "0GHIJKLMNOPQRSTUV";

#define GET_PLANEC(i)   (plane_char[i])

#define NON_ID_CHAR '?' /* non-identified character */

typedef struct _icv_state {
        char    keepc[6];       /* maximum # byte of UTF8 code */
        short   cstate;
        short   istate;
        short   ustate;
        int     _errno;         /* internal errno */
} _iconv_st;

enum _CSTATE    { C0, C1 };
enum _ISTATE    { IN, OUT };
enum _USTATE    { U0, U1, U2, U3, U4, U5, U6, U7 };


static int get_plane_no_by_utf(const char, const char, int *, unsigned long *);
static int utf8_to_iso(int, int, unsigned long, char *, size_t);
static int binsearch(unsigned long, utf_cns[], int);

/*
 * Open; called from iconv_open()
 */
void *
_icv_open()
{
        _iconv_st *st;

        if ((st = (_iconv_st *)malloc(sizeof(_iconv_st))) == NULL) {
                errno = ENOMEM;
                return ((void *) -1);
        }

        st->cstate = C0;
        st->istate = IN;
        st->ustate = U0;
        st->_errno = 0;

#ifdef DEBUG
    fprintf(stderr, "==========     iconv(): UTF2 --> ISO2022-7     ==========\n");
#endif

        return ((void *) st);
}


/*
 * Close; called from iconv_close()
 */
void
_icv_close(_iconv_st *st)
{
        if (!st)
                errno = EBADF;
        else
                free(st);
}


/*
 * Actual conversion; called from iconv()
 */
/*=========================================================
 *
 *       State Machine for interpreting UTF8 code
 *
 *=========================================================
 *                         2nd byte   3rd byte 4th byte
 *          +----->------->------->U5------>U6--------->U7
 *          |                                            |
 *          |     3 byte unicode                         |
 *          +----->------->-------+                      |
 *          |                     |                      |
 *          ^                     v                      |
 *          |  2 byte             U2 ---> U3             |
 *          |  unicode                    v              |
 * +------> U0 -------> U1                +-------->U4---+
 * ^  ascii |           |                           ^    |
 * |        |           +-------->--------->--------+    |
 * |        v                                            v
 * +----<---+-----<------------<------------<------------+
 *
 *=========================================================*/
size_t
_icv_iconv(_iconv_st *st, char **inbuf, size_t *inbytesleft,
                                char **outbuf, size_t *outbytesleft)
{
        char c1 = '\0', c2 = '\0';
        int             plane_no, n, unidx;
        /* pre_plane_no: need to be static when re-entry occurs on errno set */
        static int      pre_plane_no = -1;      /* previous plane number */
        unsigned long   cnscode;

        if (st == NULL) {
                errno = EBADF;
                return ((size_t) -1);
        }

        if (inbuf == NULL || *inbuf == NULL) { /* Reset request. */
                st->cstate = C0;
                st->istate = IN;
                st->ustate = U0;
                st->_errno = 0;
                return ((size_t) 0);
        }

#ifdef DEBUG
    fprintf(stderr, "=== (Re-entry)     iconv(): UTF-8 --> ISO 2022-7 ===\n");
    fprintf(stderr, "st->cstate=%d\tst->istate=%d\tst->_errno=%d\tplane_no=%d\n",
            st->cstate, st->istate, st->_errno, plane_no);
#endif
        st->_errno = 0;         /* reset internal errno */
        errno = 0;              /* reset external errno */

        /* a state machine for interpreting UTF8 code */
        while (*inbytesleft > 0 && *outbytesleft > 0) {

                uchar_t  first_byte;

                switch (st->ustate) {
                case U0:                /* assuming ASCII in the beginning */
                        if ((**inbuf & MSB) == 0) {     /* ASCII */
                                if (st->istate == OUT) {
                                        st->cstate = C0;
                                        st->istate = IN;
                                        **outbuf = SI;
                                        (*outbuf)++;
                                        (*outbytesleft)--;
                                        if (*outbytesleft <= 0) {
                                                errno = E2BIG;
                                                return((size_t) -1);
                                        }
                                }
                                **outbuf = **inbuf;
                                (*outbuf)++;
                                (*outbytesleft)--;
                        } else {        /* Chinese character */
                                if ((**inbuf & 0xe0) == 0xc0) { /* 2 byte unicode 0xc2..0xdf */

                                        /* invalid sequence if the first byte is either 0xc0 or 0xc1 */
                                        if ( number_of_bytes_in_utf8_char[((uchar_t)**inbuf)] == ICV_TYPE_ILLEGAL_CHAR )
                                             st->_errno = errno = EILSEQ;
                                        else {
                                             st->ustate = U1;
                                             st->keepc[0] = **inbuf;
                                        }
                                } else if ((**inbuf & 0xf0) == 0xe0) {  /* 3 byte 0xe0..0xef */
                                        st->ustate = U2;
                                        st->keepc[0] = **inbuf;
                                } else {
                                        /* four bytes of UTF-8 sequences */
                                        if ( number_of_bytes_in_utf8_char[((uchar_t)**inbuf)] == ICV_TYPE_ILLEGAL_CHAR )
                                             st->_errno = errno = EILSEQ;
                                        else
                                         {
                                             st->ustate = U5;
                                             st->keepc[0] = **inbuf;
                                         }
                                }
                        }
                        break;
                case U1:                /* 2 byte unicode */
                        if ((**inbuf & 0xc0) == 0x80) {
                                st->ustate = U4;
                                st->keepc[1] = **inbuf;
                                c1 = (st->keepc[0]&0x1c)>>2;
                                c2 = ((st->keepc[0]&0x03)<<6) | ((**inbuf)&0x3f);
#ifdef DEBUG
    fprintf(stderr, "UTF8: %02x%02x   --> ",
        st->keepc[0]&ONEBYTE, st->keepc[1]&ONEBYTE);
#endif
                                continue;       /* should not advance *inbuf */
                        } else {
                                st->_errno = errno = EILSEQ;
                        }
                        break;
                case U2:                /* 3 byte unicode - 2nd byte */

                        first_byte = st->keepc[0];

                        /* if the first byte is 0xed, it is illegal sequence if the second
                         * one is between 0xa0 and 0xbf because surrogate section is ill-formed
                         */
                        if (((uchar_t)**inbuf) < valid_min_2nd_byte[first_byte] ||
                            ((uchar_t)**inbuf) > valid_max_2nd_byte[first_byte] )
                                st->_errno = errno = EILSEQ;
                        else {
                                st->ustate = U3;
                                st->keepc[1] = **inbuf;
                        }
                        break;
                case U3:                /* 3 byte unicode - 3rd byte */
                        if ((**inbuf & 0xc0) == 0x80) {
                                st->ustate = U4;
                                st->keepc[2] = **inbuf;
                                c1 = ((st->keepc[0]&0x0f)<<4) |
                                        ((st->keepc[1]&0x3c)>>2);
                                c2 = ((st->keepc[1]&0x03)<<6) | ((**inbuf)&0x3f);
#ifdef DEBUG
    fprintf(stderr, "UTF8: %02x%02x%02x --> ", st->keepc[0]&ONEBYTE,
                st->keepc[1]&ONEBYTE, **inbuf&ONEBYTE);
#endif
                                continue;       /* should not advance *inbuf */
                        } else {
                                st->_errno = errno = EILSEQ;
                        }
                        break;
                case U4:
                        plane_no = get_plane_no_by_utf(c1, c2, &unidx, &cnscode);
                        if (plane_no == -2)
                         {  /* unicode is either 0xFFFE or 0xFFFF */
                            st->_errno = errno = EILSEQ;
                            break;
                         }

                        if (plane_no > 0) {     /* legal unicode; illegal CNS */
                        if ((st->istate == IN) || (pre_plane_no != plane_no)) {
                                if ((st->cstate == C0) ||
                                        (pre_plane_no != plane_no)) {
                                        /* change plane # in Chinese mode */
                                        if (st->cstate == C1) {
                                                **outbuf = SI;
                                                (*outbuf)++;
                                                (*outbytesleft)--;
                                        }
                                        if (*outbytesleft < 4) {
                                                st->_errno = errno = E2BIG;
                                                return((size_t) -1);
                                        }
                                        pre_plane_no = plane_no;
                                        st->cstate = C1;
                                        **outbuf = ESC;
                                        *(*outbuf+1) = '$';
                                        *(*outbuf+2) = ')';
                                        *(*outbuf+3) = GET_PLANEC(plane_no);
#ifdef DEBUG
    fprintf(stderr, "\n\t\t\t\tESC $ ) %c\t", *(*outbuf+3));
#endif
                                        (*outbuf) += 4;
                                        (*outbytesleft) -= 4;
                                        if (*outbytesleft <= 0) {
                                                st->_errno = errno = E2BIG;
                                                return((size_t) -1);
                                        }
                                }
                                st->istate = OUT;
                                **outbuf = SO;
                                (*outbuf)++;
                                (*outbytesleft)--;
                        }
                        }/* get_plane_no OK */

                        n = utf8_to_iso(plane_no, unidx, cnscode,
                                        *outbuf, *outbytesleft);
                        if (n > 0) {
                                (*outbuf) += n;
                                (*outbytesleft) -= n;
                        } else {
                                st->_errno = errno;
                                return((size_t) -1);
                        }
                        st->ustate = U0;
                        st->_errno = 0;
                        break;
                case U5:

                        first_byte = st->keepc[0];

                        /* if the first byte is 0xed, it is illegal sequence if the second
                         * one is between 0xa0 and 0xbf because surrogate section is ill-formed
                         */
                        if (((uchar_t)**inbuf) < valid_min_2nd_byte[first_byte] ||
                            ((uchar_t)**inbuf) > valid_max_2nd_byte[first_byte] )
                                st->_errno = errno = EILSEQ;
                        else {
                                st->ustate = U6;
                                st->keepc[1] = **inbuf;
                        }
                        break;
                case U6:
                        if ((**inbuf & 0xc0) == MSB) /* 0x80..0xbf */
                          {
                             st->ustate = U7;
                             st->keepc[2] = **inbuf;
                          }
                        else
                             st->_errno = errno = EILSEQ;
                        break;
                case U7:
                        if ((**inbuf & 0xc0) == MSB) /* 0x80..0xbf */
                          {  /* skip it to simplify */
                             st->ustate = U0;
                             st->_errno = 0;
                          }
                        else
                             st->_errno = errno = EILSEQ;
                        break;
                default:                        /* should never come here */
                        st->_errno = errno = EILSEQ;
                        st->ustate = U0;        /* reset state */
                        break;
                }

                if (st->_errno) {
#ifdef DEBUG
    fprintf(stderr, "!!!!!\tst->_errno = %d\tst->ustate = %d\n",
                st->_errno, st->ustate);
#endif
                        break;
                }
                (*inbuf)++;
                (*inbytesleft)--;
        }

        if (errno)
                return((size_t) -1);

        if (*inbytesleft == 0 && st->ustate != U0) {
                errno = EINVAL;
                return ((size_t) -1);
        }

        if (*inbytesleft > 0 && *outbytesleft == 0) {
                errno = E2BIG;
                return((size_t) -1);
        }
        return (*inbytesleft);
}


/*
 * Get plane number by UTF8 code; i.e. plane #1 returns 1, #2 returns 2, etc.
 * Returns -1 on error conditions and return -2 due to illegal sequence
 *
 * Since binary search of the UTF8 to CNS table is necessary, might as well
 * return index and CNS code matching to the unicode.
 */
static int get_plane_no_by_utf(const char c1, const char c2,
                        int *unidx, unsigned long *cnscode)
{
        int             ret;
        unsigned long   unicode;

        unicode = (unsigned long) ((c1 & ONEBYTE) << 8) + (c2 & ONEBYTE);
        /* the 0xfffe and 0xffff should not be allowed */
        if ( unicode == 0xFFFE || unicode == 0xFFFF ) return -2;

        *unidx = binsearch(unicode, utf_cns_tab, MAX_UTF_NUM);
        if ((*unidx) >= 0)
                *cnscode = utf_cns_tab[*unidx].cnscode;
        else
                return(0);      /* match from UTF8 to CNS not found */
#ifdef DEBUG
    fprintf(stderr, "Unicode=%04x, idx=%5d, CNS=%x ", unicode, *unidx, *cnscode);
#endif

        ret = (int) (*cnscode >> 16);
        switch (ret) {
        case 0x21:      /* 0x8EA1 - G */
        case 0x22:      /* 0x8EA2 - H */
        case 0x23:      /* 0x8EA3 - I */
        case 0x24:      /* 0x8EA4 - J */
        case 0x25:      /* 0x8EA5 - K */
        case 0x26:      /* 0x8EA6 - L */
        case 0x27:      /* 0x8EA7 - M */
        case 0x28:      /* 0x8EA8 - N */
        case 0x29:      /* 0x8EA9 - O */
        case 0x2a:      /* 0x8EAA - P */
        case 0x2b:      /* 0x8EAB - Q */
        case 0x2c:      /* 0x8EAC - R */
        case 0x2d:      /* 0x8EAD - S */
        case 0x2f:      /* 0x8EAF - U */
        case 0x30:      /* 0x8EB0 - V */
                return (ret - 0x20);    /* so that we can use GET_PLANEC() */
        case 0x2e:      /* 0x8EAE - T */
                return (3);             /* CNS 11643-1992 */
        default:
                return (-1);
        }
}


/*
 * ISO/IEC 10646 (Unicode) --> ISO 2022-7
 * Unicode --> UTF8 (FSS-UTF)
 *             (File System Safe Universal Character Set Transformation Format)
 * Return: > 0 - converted with enough space in output buffer
 *         = 0 - no space in outbuf
 */
static int utf8_to_iso(int plane_no, int unidx, unsigned long cnscode,
                                                    char *buf, size_t buflen)
{
        unsigned long   val;            /* CNS 11643 value */
#ifdef DEBUG
    char        cns_str[5];
#endif

        if (buflen < 2) {
                errno = E2BIG;
                return(0);
        }


        if (unidx < 0) {        /* no match from UTF8 to CNS 11643 */
            *buf = *(buf+1) = NON_ID_CHAR;
            return(2);
        } else {
                val = cnscode & 0xffff;
                *buf = (val & 0xff00) >> 8;
                *(buf+1) = val & 0xff;
        }
#ifdef DEBUG
    fprintf(stderr, "\t%02x%02x\t", *buf, *(buf+1));
#endif

#ifdef DEBUG
    switch (plane_no) {
    case 1:
        cns_str[0] = *buf | MSB;
        cns_str[1] = *(buf+1) | MSB;
        cns_str[2] = cns_str[3] = cns_str[4] = NULL;
        break;
    case 2:
    case 3:
    case 4:
    case 5:
    case 6:
    case 7:
    case 8:
    case 9:
    case 10:
    case 11:
    case 12:
    case 13:
    case 14:
    case 15:
    case 16:
        cns_str[0] = MBYTE;
        cns_str[1] = (char) PMASK + plane_no;
        cns_str[2] = (char) *buf | MSB;
        cns_str[3] = (char) *(buf+1) | MSB;
        cns_str[4] = NULL;
        break;
    }

    fprintf(stderr, "#%d ->%s<-\n", plane_no, cns_str);
#endif
        return(2);
}


/* binsearch: find x in v[0] <= v[1] <= ... <= v[n-1] */
static int binsearch(unsigned long x, utf_cns v[], int n)
{
        int low, high, mid;

        low = 0;
        high = n - 1;
        while (low <= high) {
                mid = (low + high) / 2;
                if (x < v[mid].unicode)
                        high = mid - 1;
                else if (x > v[mid].unicode)
                        low = mid + 1;
                else    /* found match */
                        return mid;
        }
        return (-1);    /* no match */
}