/*
 * 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) 2000, by Sun Microsystems, Inc.
 * All rights reserved.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/isa_defs.h>
#include "unicode_big5hk.h"     /* UTF8 to HKSCS mapping table */
#include "common_defs.h"

#define MSB     0x80    /* most significant bit */
#define ONEBYTE 0xff    /* right most byte */

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

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

enum _USTATE    { U0, U1, U2, U3, U4, U5, U6, U7 };

static int get_hkscs_by_utf(uint_t, int *, unsigned long *);
static int utf8_to_hkscs(int, unsigned long, char *, size_t, int *);
static int binsearch(unsigned long, utf_hkscs[], 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->ustate = U0;
        st->_errno = 0;
        st->little_endian = false;
        st->bom_written = false;
#if defined(UCS_2LE)
        st->little_endian = true;
        st->bom_written = true;
#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        v
 * +------> U0 -------> U1                +-------->U4---+
 * ^  ascii |           |                           ^    |
 * |        |           +-------->--------->--------+    |
 * |        v                                            v
 * +----<---+-----<------------<------------<------------+
 *
 *=========================================================*/
size_t
_icv_iconv(_iconv_st *st, char **inbuf, size_t *inbytesleft,
                                char **outbuf, size_t *outbytesleft)
{
        int             utf8_len = 0;
        int             n, unidx;
        unsigned long   hkscscode;
        int             uconv_num = 0;
        uint_t          ucs;

#ifdef DEBUG
    fprintf(stderr, "==========     iconv(): UTF2 --> HKSCS     ==========\n");
#endif
        if (st == NULL) {
                errno = EBADF;
                return ((size_t) -1);
        }

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

        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;
                int      uconv_num_internal = 0;

                switch (st->ustate) {
                case U0:                /* assuming ASCII in the beginning */
                       /*
                        * Code converion for UCS-2LE to support Samba
                        */
                        if (st->little_endian) {
                          st->ustate = U1;
                          st->keepc[0] = **inbuf;
                        }
                        else if ((**inbuf & MSB) == 0) {        /* ASCII */
                                **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) == MSB || st->little_endian) {
                                st->keepc[1] = **inbuf;
                                utf8_len = 2;

                                /*
                                 * Code conversion for UCS-2LE to support Samba
                                 */
                                if  (st->little_endian) {
                                  /*
                                   * It's ASCII
                                   */
                                  if (st->keepc[1] == 0 && (st->keepc[0] & 0x80) == 0) {
                                    *(*outbuf)++ = st->keepc[0];
                                    (*outbytesleft)--;
                                    st->ustate = U0;
                                    break;
                                  }

                                  ucs = ((st->keepc[1] & 0xff) << 8) | ( st->keepc[0] & 0xff);

                                } else
                                  convert_utf8_to_ucs4((uchar_t*)(&st->keepc[0]), utf8_len, &ucs);

                                st->ustate = U4;
#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) == MSB) {
                                st->ustate = U4;
                                st->keepc[2] = **inbuf;
                                utf8_len = 3;

                                convert_utf8_to_ucs4((uchar_t*)(&st->keepc[0]), utf8_len, &ucs);
#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:
                        n = get_hkscs_by_utf(ucs, &unidx, &hkscscode);
                        if ( n == -1 ) { /* unicode is either 0xfffe or 0xffff */
                                st->_errno = errno = EILSEQ;
                                break;
                        }

/* comment the following lines out to ignore the non-Big5 characters
g                       if (n != 0) {
                                st->_errno = errno = EILSEQ;
                                break;
                        }
*/

                        n = utf8_to_hkscs(unidx, hkscscode,
                                        *outbuf, *outbytesleft, &uconv_num_internal);
                        if (n > 0) {
                                (*outbuf) += n;
                                (*outbytesleft) -= n;

                                uconv_num += uconv_num_internal;

                                st->ustate = U0;
                        } else {
                                st->_errno = errno;
                        }
                        break;
                case U5:

                        first_byte = st->keepc[0];

                        /* if the first byte is 0xf0, it is illegal sequence if
                         * the second one is between 0x80 and 0x8f
                         * for Four-Byte UTF: U+10000..U+10FFFF
                         */
                        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 */
                          {
                             utf8_len = 4;
                             st->keepc[3] = **inbuf;

                             convert_utf8_to_ucs4((uchar_t*)(&st->keepc[0]), utf8_len, &ucs);

                             st->ustate = U4;
                             continue;  /* should not advance *inbuf */
                          }
                        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;

        if (*inbytesleft > 0 && *outbytesleft == 0)
                errno = E2BIG;

        if (errno) {
                int num_reversed_bytes = 0;

                switch (st->ustate)
                {
                 case U1:
                   num_reversed_bytes = 1;
                   break;
                 case U2:
                   num_reversed_bytes = 1;
                   break;
                 case U3:
                   num_reversed_bytes = 2;
                   break;
                 case U4:
                   num_reversed_bytes = utf8_len - 1;
                   break;
                 case U5:
                   num_reversed_bytes = 1;
                   break;
                 case U6:
                   num_reversed_bytes = 2;
                   break;
                 case U7:
                   num_reversed_bytes = 3;
                   break;
                }

                /*
                 * if error, *inbuf points to the byte following the last byte
                 * successfully used in the conversion.
                 */
                *inbuf -= num_reversed_bytes;
                *inbytesleft += num_reversed_bytes;
                st->ustate = U0;
                return ((size_t) -1);
        }

        return uconv_num;
}

/*
 * Match HKSCS code by UTF8 code;
 * Return: = 0 - match from Unicode to HKSCS found
 *         = 1 - match from Unicode to HKSCS NOT found
 *         =-1 - illegal sequence
 *
 * Since binary search of the UTF8 to HKSCS table is necessary, might as well
 * return index and HKSCS code matching to the unicode.
 */
static int get_hkscs_by_utf(uint_t unicode, int *unidx, unsigned long *hkscscode)
{
        /* the 0xFFFE and 0xFFFF should not be allowed */
        if (unicode == 0xFFFE || unicode == 0xFFFF ) return -1;

        *unidx = binsearch(unicode, utf_hkscs_tab, MAX_HKSCS_NUM);
        if ((*unidx) >= 0)
                *hkscscode = utf_hkscs_tab[*unidx].hkscscode;
        else
                return(1);      /* match from UTF8 to HKSCS not found */
#ifdef DEBUG
    fprintf(stderr, "Unicode=%04x, idx=%5d, HKSCS=%x ", unicode, *unidx, *hkscscode);
#endif

        return(0);
}


/*
 * ISO/IEC 10646 (Unicode) --> HKSCS
 * 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_hkscs(int unidx, unsigned long hkscscode, char *buf, size_t buflen, int *uconv_num)
{
        unsigned long   val;            /* HKSCS value */
        char            c1, c2, hkscs_str[3];

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

        if (unidx < 0) {        /* no match from UTF8 to HKSCS */
                *buf = *(buf+1) = NON_ID_CHAR;

                /* non-identical conversion */
                *uconv_num = 1;
        } else {
                val = hkscscode & 0xffff;
                c1 = (char) ((val & 0xff00) >> 8);
                c2 = (char) (val & 0xff);

        *buf = hkscs_str[0] = c1;
        *(buf+1) = hkscs_str[1] = c2;
        hkscs_str[2] = '\0';
        }

#ifdef DEBUG
    fprintf(stderr, "\t->%x %x<-\n", *buf, *(buf+1));
#endif

        return(2);
}


/* binsearch: find x in v[0] <= v[1] <= ... <= v[n-1] */
static int binsearch(unsigned long x, utf_hkscs 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 */
}