/*
 * 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) 1998 Sun Microsystems, Inc.
 */

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unicode_gb2312.h>
#include "common_defs.h"

#define SI      0x0f
#define SO      0x0e
#define ESC     0x1b
#define MSB     0x80

#define NON_ID_CHAR '?'

typedef struct _icv_state {
        short   _ustate;
        short   _istate;
        short   _gstate;
        char    _cbuf[3];
} _iconv_st;

enum    _USTATE { U0, U1, U2, U3, U4, U5, U6 };
enum    _ISTATE { IN, OUT };
enum    _GSTATE { G0, G1 };

int unicode_to_iso(char in_byte1, char in_byte2, char *buf, int buflen);

/*
 * 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->_istate = IN;
        st->_gstate = G0;

        return ((void *)st);
}


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


/*
 * Actual conversion; called from iconv()
 */
size_t
_icv_iconv(_iconv_st *st, char **inbuf, size_t*inbytesleft,
                        char **outbuf, size_t*outbytesleft)
{
        char    c1, c2;
        int     n;

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

        if (inbuf == NULL || *inbuf == NULL) { /* Reset request. */
                st->_ustate = U0;
                st->_istate = IN;
                st->_gstate = G0;
                return ((size_t)0);
        }

        errno = 0;

        while (*inbytesleft > 0 && *outbytesleft > 0) {

            uchar_t  first_byte;

            switch (st->_ustate) {
            case U0:
                if ((**inbuf & MSB) == 0) {     /* ASCII */
                    if (st->_istate == OUT) {
                        st->_istate = IN;
                        **outbuf = SI;
                        (*outbuf)++, (*outbytesleft)--;
                        if (*outbytesleft <= 0) {
                            errno = E2BIG;
                            return ((size_t)-1);
                        }
                    }
                    **outbuf = **inbuf;
                    (*outbuf)++, (*outbytesleft)--;
                } else {
                    if ((**inbuf & 0xe0) == 0xc0) { /* 0xc2..0xdf */

                        /* invalid sequence if the first char is either 0xc0 or 0xc1 */
                        if ( number_of_bytes_in_utf8_char[((uchar_t)**inbuf)] == ICV_TYPE_ILLEGAL_CHAR )
                         {
                            errno = EILSEQ;
                            break;
                         }
                        else
                         {
                             st->_ustate = U1;
                             st->_cbuf[0] = **inbuf;
                         }
                    } else if ((**inbuf & 0xf0) == 0xe0) { /* 0xe0..0xef */
                        st->_ustate = U2;
                        st->_cbuf[0] = **inbuf;
                    } else {
                        /* four bytes of UTF-8 sequences */
                        if ( number_of_bytes_in_utf8_char[((uchar_t)**inbuf)] == ICV_TYPE_ILLEGAL_CHAR )
                          {
                            errno = EILSEQ;
                            break;
                           }
                        else {
                           st->_ustate = U4;
                           st->_cbuf[0] = **inbuf;
                        }
                    }
                    if (st->_istate == IN) {
                        if (st->_gstate == G0) {
                            if (*outbytesleft < 4) {
                                errno = E2BIG;
                                return ((size_t)-1);
                            }
                            st->_gstate = G1;
                            **outbuf = ESC;
                            *(*outbuf+1) = '$';
                            *(*outbuf+2) = ')';
                            *(*outbuf+3) = 'A';
                            (*outbuf) += 4, (*outbytesleft) -= 4;
                            if (*outbytesleft <= 0) {
                                errno = E2BIG;
                                return ((size_t)-1);
                            }
                        }
                        st->_istate = OUT;
                        **outbuf = SO;
                        (*outbuf)++, (*outbytesleft)--;
                    }
                }
                break;
            case U1:
                if ((**inbuf & 0xc0) == MSB) {  /* two-byte UTF */
                    c1 = (st->_cbuf[0]&0x1c)>>2;
                    c2 = ((st->_cbuf[0]&0x03)<<6) | ((**inbuf)&0x3f);
                    n = unicode_to_iso(c1, c2, *outbuf, *outbytesleft);
                    if (n > 0) {
                        (*outbuf) += n, (*outbytesleft) -= n;
                    } else {
                        errno = E2BIG;
                        return ((size_t)-1);
                    }
                    st->_ustate = U0;
                } else {
                    errno = EILSEQ;
                }
                break;
            case U2:

                first_byte = st->_cbuf[0];

                /* if the first byte is 0xed, it is illegal sequence if the second
                 * one is one 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] )
                     errno = EILSEQ;
                else {
                     st->_ustate = U3;
                     st->_cbuf[1] = **inbuf;
                }
                break;
            case U3:
                if ((**inbuf & 0xc0) == MSB) {  /* three-byte UTF */
                    c1 = ((st->_cbuf[0]&0x0f)<<4) | ((st->_cbuf[1]&0x3c)>>2);
                    c2 = ((st->_cbuf[1]&0x03)<<6) | ((**inbuf)&0x3f);
                    n = unicode_to_iso(c1, c2, *outbuf, *outbytesleft);
                    if (n > 0) {
                        (*outbuf) += n, (*outbytesleft) -= n;
                    } else if ( n == -1 ) {
                        errno = EILSEQ; /* unicode is either 0xfffe or 0xffff */
                    } else {
                        errno = E2BIG;
                        return ((size_t)-1);
                    }
                    st->_ustate = U0;
                } else {
                    errno = EILSEQ;
                }
                break;
             case U4:
                first_byte = st->_cbuf[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] )
                     errno = EILSEQ;
                else {
                     st->_ustate = U5;
                     st->_cbuf[1] = **inbuf;
                }
                break;
             case U5:
                if ((**inbuf & 0xc0) == MSB) /* 0x80..0xbf */
                  {
                     st->_ustate = U6;
                     st->_cbuf[2] = **inbuf;
                  }
                else
                     errno = EILSEQ;
                break;
             case U6:
                if ((**inbuf & 0xc0) == MSB) /* 0x80..0xbf */
                   {
                      /* replace with double NON_ID_CHARs */
                      if ( *outbytesleft < 2 )
                         errno = E2BIG;
                      else
                        {
                           **outbuf = NON_ID_CHAR;
                           *(*outbuf+1) = NON_ID_CHAR;
                           (*outbytesleft) -= 2;

                           st->_ustate = U0;
                        }
                   }
                else
                     errno = EILSEQ;
                break;
            }

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

            (*inbuf)++; (*inbytesleft)--;
        }

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

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


int unicode_to_iso(in_byte1, in_byte2, buf, buflen)
char    in_byte1, in_byte2;
char    *buf;
int     buflen;
{
        int     gb, unicode;
        int     i, l, h;

        if (buflen < 2)
                return 0;
        unicode = ((in_byte1 & 0xff) << 8) + (in_byte2 & 0xff);

        /* 0xfffe and 0xffff should not be allowed */
        if ( unicode == 0xFFFE || unicode == 0xFFFF ) return -1;

        for (l = 0, h = UNICODEMAX; l < h; ) {
                if (unicode_gb_tab[l].key == unicode) {
                        i = l;
                        break;
                }
                if (unicode_gb_tab[h].key == unicode) {
                        i = h;
                        break;
                }
                i = (l + h) / 2;
                if (unicode_gb_tab[i].key == unicode)
                        break;
                if (unicode_gb_tab[i].key < unicode)
                        l = i + 1;
                else    h = i - 1;
        }
        if (unicode == unicode_gb_tab[i].key) {
                gb = unicode_gb_tab[i].value;
                *buf = (gb & 0xff00) >> 8;
                *(buf+1) = gb & 0xff;
        } else {
                *buf = *(buf+1) = NON_ID_CHAR;
        }
        return 2;
}