/*
 * 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.
 *      All rights reserved.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <big5_gb18030.h>

#define NON_ID_CHAR '_' /* non-identifier charactor */
#define MSB 0x80
#define ONEBYTE 0xff

typedef struct _icv_state {
        char keepc[2];  /* maximum # byte of BIG5 charactor */
        short cstate;
        int _errno;             /* internal errno */
} _iconv_st;

enum _CSTATE { C0, C1 };

int big5_2nd_byte(char inbuf);
int big5_to_gbk(char keepc[], char *buf, size_t buflen);
int binsearch(unsigned long x, table_t table[], int n);

/*
 *      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) {    /* big5 charactor */
                                        st->keepc[0] = (**inbuf);
                                        st->cstate = C1;
                                } else {        /* ASCII */
                                        **outbuf = **inbuf;
                                        (*outbuf)++;
                                        (*outbytesleft)--;
                                }
                                break;
                        case C1:        /* Big5 charactor 2nd byte */
                                if (big5_2nd_byte(**inbuf) == 0) {
                                        st->keepc[1] = (**inbuf);
                                        n = big5_to_gbk(st->keepc, *outbuf, *outbytesleft);
                                        if (n > 0) {
                                                (*outbuf) += n;
                                                (*outbytesleft) -= n;

                                                st->cstate = C0;
                                        } else {
                                                st->_errno = errno = E2BIG;
                                        }
                                } else {        /* illegal input */
                                        st->_errno = errno =EILSEQ;
                                }
                                break;
                        default:
                                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 BIG5 charactor:
 *      Return: 0 --- valid BIG5 2nd byte
 *                      1 --- invalid BIG5 2nd byte
 */
int big5_2nd_byte(inbuf)
char inbuf;
{
        unsigned int buf = (unsigned int)(inbuf & ONEBYTE);

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

/*
 *      big5_to_gbk: Convert Big5 to gbk.
 *      Return: >0 --- converted with enough space in output buffer
 *                      =0 --- no space in outbuf
 */

int big5_to_gbk(char keepc[], char *buf, size_t buflen) {

        unsigned long gbk_val;
        int index;
        unsigned long big5_val;

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

        big5_val = ((keepc[0] & ONEBYTE) << 8) + (keepc[1] & ONEBYTE);
        index = binsearch(big5_val, big5_gbk_tab, BIG5MAX);
        if (index >= 0) {
                gbk_val = big5_gbk_tab[index].value;
                *buf = (gbk_val >> 8) & ONEBYTE;
                *(buf + 1) = gbk_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;
}