/*
 * 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) 1997, Sun Microsystems, Inc.
 *      All rights reserved.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <gb18030_big5.h>

#define NON_ID_CHAR '_' /* non-identified character */
#define MSB 0x80
#define ONEBYTE 0xff

#define gbk4_2nd_byte(v)  ( (v) >= 0x30 && (v) <= 0x39 )
#define gbk4_3rd_byte(v)   ( (v) >= 0x81 && (v) <= 0xfe )
#define gbk4_4th_byte(v)  gbk4_2nd_byte(v)

typedef struct _icv_state {
        char keepc[2];  /* maximum # byte of GB chararor in two bytes area */
        short cstate;
        int _errno;             /* internal errno */
} _iconv_st;

enum _CSTATE { C0, C1, C2, C3 };

int binsearch(unsigned long x, table_t table[], int n);
int gbk_2nd_byte(char inbuf);
int gbk_to_big5(char keepc[], char *buf, size_t buflen);

/*=======================================================
 *
 *   State Machine for interpreting GBK code
 *
 *=======================================================
 *
 *                                  3rd C
 *                              C2--------> C3
 *                              ^            |
 *                        2nd C |      4th C |
 *                     1st C    |            |
 *    +--------> C0 ----------> C1           |
 *    |    ascii |        2nd C |            |
 *    ^          v              v            V
 *    +----<-----+-----<--------+-----<------+
 *
 *=======================================================*/
/*
 *      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->_errno = 0;

        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()
 */

size_t _icv_iconv(_iconv_st * st, char **inbuf, size_t *inbytesleft,
                                        char ** outbuf, size_t *outbytesleft) {
        int n;
        if (st == NULL) {
                errno = EBADF;
                return ((size_t) -1);
        }

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

        errno = st->_errno = 0;

        while (*inbytesleft > 0 && *outbytesleft > 0) {
                switch (st->cstate) {
                        case C0:
                                if (**inbuf & MSB) {    /* gb2312 charactor */
                                        st->keepc[0] = (**inbuf);
                                        st->cstate = C1;
                                } else {        /* ASCII */
                                        **outbuf = **inbuf;
                                        (*outbuf)++;
                                        (*outbytesleft)--;
                                }
                                break;
                        case C1:        /* GBK charactor 2nd byte */
                                if (gbk_2nd_byte(**inbuf) == 0) {
                                        st->keepc[1] = (**inbuf);
                                        n = gbk_to_big5(st->keepc, *outbuf, *outbytesleft);
                                        if (n > 0) {
                                                (*outbuf) += n;
                                                (*outbytesleft) -= n;

                                                st->cstate = C0;
                                        } else {
                                                st->_errno = errno = E2BIG;
                                        }
                                } else if ( gbk4_2nd_byte((unsigned char)**inbuf) ) {
                                        st->cstate = C2;
                                } else {        /* illegal input */
                                        st->_errno = errno = EILSEQ;
                                }
                                break;
                        case C2:
                                if ( gbk4_3rd_byte((unsigned char)**inbuf) ) {
                                        st->cstate = C3;
                                } else {
                                        st->_errno = errno = EILSEQ;
                                }
                                break;
                        case C3:
                                if ( gbk4_4th_byte((unsigned char)**inbuf) ) {
                                        /*
                                         *  replace the four byte character with "__" in outbuf
                                         *  due to that there hasn't corresponding code in BIG5
                                         */
                                        if ( *outbytesleft < 2 ) {
                                                st->_errno = errno = E2BIG;
                                        } else {
                                                **outbuf = *((*outbuf) + 1) = (char)NON_ID_CHAR;
                                                *outbuf += 2;
                                                *outbytesleft -= 2;

                                                st->cstate = C0;
                                        }
                                } else {
                                        st->_errno = errno = EILSEQ;
                                }
                                break;
                        default:        /* un-reachable */
                                st->_errno = errno = EILSEQ;
                                st->cstate = C0;
                                break;
                }

                if ( st->_errno ) break;

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

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

        if (*inbytesleft == 0 && st->cstate != C0) {
                errno = EINVAL;
                return ((size_t) -1);
        }

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

        return (size_t)(*inbytesleft);
}

/*
 *      Test whether inbuf is a valid character for
 *      2nd byte of GB2312 charactor:
 *      Return: 0 --- valid GBK 2nd byte
 *                      1 --- invalid GBK 2nd byte
 */
int gbk_2nd_byte(inbuf)
char inbuf;
{

        unsigned int buf = (unsigned int) (inbuf & ONEBYTE);

        if ((buf >= 0x40) && (buf <= 0x7e))
                return 0;
        if ((buf >= 0x80) && (buf <= 0xfe))
                return 0;
        return 1;
}

/*
 *      gbk_to_big5: Convert gbk charactor to Big5.
 *      Return: >0 --- converted with enough space in output buffer
 *                      =0 --- no space in outbuf
 */

int gbk_to_big5(char keepc[], char *buf, size_t buflen) {

        unsigned long gbk_val;  /* GBK value */
        int index;
        unsigned long big5_val; /* BIG5 value */

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

        gbk_val = ((keepc[0] & ONEBYTE) << 8) + (keepc[1] & ONEBYTE);
        index = binsearch(gbk_val, gbk_big5_tab, BIG5MAX);
        if (index >= 0) {
                big5_val = gbk_big5_tab[index].value;
                *buf = (big5_val >> 8) & ONEBYTE;
                *(buf + 1) = big5_val & ONEBYTE;
        } else
                *buf = *(buf + 1) = (char)NON_ID_CHAR;
        return 2;
}

/*
 *      binsearch()
 */
int binsearch(unsigned long x, table_t table[], int n) {
        int low, high, mid;

        low = 0;
        high = n - 1;
        while (low <= high) {
                mid = (low + high) >> 1;
                if (x < table[mid].key)
                        high = mid - 1;
                else if (x > table[mid].key)
                        low = mid + 1;
                else
                        return mid;
        }
        return -1;
}

#ifdef DEBUG
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

int
main(int argc, char * argv[]) {
        _iconv_st * ist;
        char * inbuf = "\xd2\xd4\xcf\xc2\xcb\xf9\xc1\xd0\xb5\xc4\xc3\xbf\xd2"
            "\xbb\xb1\xea\xcc\xe2\xb4\xfa\xb1\xed\xd2\xbb\xb8\xf6\xd2\xd1\xb0"
            "\xb2\xd7\xb0\xb2\xa2\xd7\xa2\xb2\xe1\xc1\xcb\xc1\xaa\xbb\xfa\xcc"
            "\xe1\xca\xbe\xb5\xc4\x20\xb2\xfa\xc6\xb7\xcf\xb5\xc1\xd0\x20\xa1"
            "\xa3";
        char * outbuf;
        char * ib, * oub;
        size_t inbyteleft;
        size_t outbyteleft;

        ist = (_iconv_st *) _icv_open();
        inbyteleft = outbyteleft = 2 * strlen(inbuf);
        outbuf = (char *)malloc(outbyteleft);
        ib = inbuf;
        oub = outbuf;
        _icv_iconv(ist, &inbuf, &inbyteleft, &outbuf, &outbyteleft);
        printf("IN -- %s\n", ib);
        printf("OUT -- %s\n", oub);

        return (0);
}
#endif