path: root/innbbsd/str_decode.c

/*
 * 使用方法大致如下: innbbsd 中 在 SUBJECT 從 news 讀進來後, 呼叫
 * str_decode_M3(SUBJECT) 就行了
 */

/*
 * bsd 底下使用要編譯時要加  -I/usr/local/include -L/usr/local/lib -liconv
 * 並安裝 libiconv, 若真的沒有iconv就把底下的 #define USE_ICONV 1 刪了
 */

/*-------------------------------------------------------*/
/* lib/str_decode.c ( NTHU CS MapleBBS Ver 3.00 )    */
/*-------------------------------------------------------*/
/* target : included C for QP/BASE64 decoding        */
/* create : 95/03/29                     */
/* update : 97/03/29                     */
/*-------------------------------------------------------*/


/* ----------------------------------------------------- */
/* QP code : "0123456789ABCDEF"              */
/* ----------------------------------------------------- */

#include <stdio.h>
#include <errno.h>
#include <string.h>

#define USE_ICONV 1
/*
 * bsd 底下使用要編譯時要加  -I/usr/local/include -L/usr/local/lib -liconv
 * 若真的沒有iconv就把上面這行 #define 刪了
 */

#ifdef USE_ICONV
#include <iconv.h>
#endif

static int 
qp_code(int x)
{
    if (x >= '0' && x <= '9')
    return x - '0';
    if (x >= 'a' && x <= 'f')
    return x - 'a' + 10;
    if (x >= 'A' && x <= 'F')
    return x - 'A' + 10;
    return -1;
}


/* ------------------------------------------------------------------ */
/* BASE64 :                               */
/* "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" */
/* ------------------------------------------------------------------ */


static int 
base64_code(int x)
{
    if (x >= 'A' && x <= 'Z')
    return x - 'A';
    if (x >= 'a' && x <= 'z')
    return x - 'a' + 26;
    if (x >= '0' && x <= '9')
    return x - '0' + 52;
    if (x == '+')
    return 62;
    if (x == '/')
    return 63;
    return -1;
}


/* ----------------------------------------------------- */
/* judge & decode QP / BASE64                */
/* ----------------------------------------------------- */

static inline int 
isreturn(unsigned char c)
{
    return c == '\r' || c == '\n';
}

static inline int 
isspace(unsigned char c)
{
    return c == ' ' || c == '\t' || isreturn(c);
}

/* static inline */
int 
mmdecode(unsigned char *src, unsigned char encode, unsigned char *dst)
{
    /* Thor.980901: src和dst可相同, 但src 一定有?或\0結束 */
    /* Thor.980901: 注意, decode出的結果不會自己加上 \0 */
    unsigned char  *t = dst;
    int             pattern = 0, bits = 0;
    encode |= 0x20;     /* Thor: to lower */
    switch (encode) {
    case 'q':           /* Thor: quoted-printable */
    while (*src && *src != '?') {   /* Thor: delimiter *//* Thor.980901:
                     * 0 算是 delimiter */
        if (*src == '=') {
        int             x = *++src, y = x ? *++src : 0;
        if (isreturn(x))
            continue;
        if ((x = qp_code(x)) < 0 || (y = qp_code(y)) < 0)
            return -1;
        *t++ = (x << 4) + y, src++;
        } else if (*src == '_')
        *t++ = ' ', src++;
#if 0
        else if (!*src) /* Thor: no delimiter is not successful */
        return -1;
#endif
        else        /* Thor: *src != '=' '_' */
        *t++ = *src++;
    }
    return t - dst;
    case 'b':           /* Thor: base 64 */
    while (*src && *src != '?') {   /* Thor: delimiter */
        /*
         * Thor.980901: 0也算 *//* Thor: pattern & bits are cleared
         * outside
         */
        int             x;
#if 0
        if (!*src)
        return -1;  /* Thor: no delimiter is not successful */
#endif
        x = base64_code(*src++);
        if (x < 0)
        continue;   /* Thor: ignore everything not in the
                 * base64,=,.. */
        pattern = (pattern << 6) | x;
        bits += 6;      /* Thor: 1 code gains 6 bits */
        if (bits >= 8) {    /* Thor: enough to form a byte */
        bits -= 8;
        *t++ = (pattern >> bits) & 0xff;
        }
    }
    return t - dst;
    }
    return -1;
}

#ifdef USE_ICONV
size_t 
str_iconv(
      const char *fromcode, /* charset of source string */
      const char *tocode,   /* charset of destination string */
      char *src,        /* source string */
      size_t srclen,        /* source string length */
      char *dst,        /* destination string */
      size_t dstlen)
{               /* destination string length */
    /*
     * 這個函式會將一個字串 (src) 從 charset=fromcode 轉成 charset=tocode,
     * srclen 是 src 的長度, dst 是輸出的buffer, dstlen 則指定了 dst 的大小,
     * 最後會補 '\0', 所以要留一個byte給'\0'. 如果遇到 src 中有非字集的字,
     * 或是 src 中有未完整的 byte, 都會砍掉.
     */
    iconv_t         iconv_descriptor;
    size_t          iconv_ret, dstlen_old;

    dstlen--;           /* keep space for '\0' */

    dstlen_old = dstlen;

    /* Open a descriptor for iconv */
    iconv_descriptor = iconv_open(tocode, fromcode);

    if (iconv_descriptor == ((iconv_t) (-1))) { /* if open fail */
    strncpy(dst, src, dstlen);
    return dstlen;
    }
    /* Start translation */
    while (srclen > 0 && dstlen > 0) {
    iconv_ret = iconv(iconv_descriptor, (const char **)&src, &srclen,
              &dst, &dstlen);
    if (iconv_ret != 0) {
        switch (errno) {
        /* invalid multibyte happened */
        case EILSEQ:
        /* forward that byte */
        *dst = *src;
        src++;
        srclen--;
        dst++;
        dstlen--;
        break;
        /* incomplete multibyte happened */
        case EINVAL:
        /* forward that byte (maybe wrong) */
        *dst = *src;
        src++;
        srclen--;
        dst++;
        dstlen--;
        break;
        /* dst no rooms */
        case E2BIG:
        /* break out the while loop */
        srclen = 0;
        break;
        }
    }
    }
    *dst = '\0';
    /* close descriptor of iconv */
    iconv_close(iconv_descriptor);

    return (dstlen_old - dstlen);
}
#endif


void 
str_decode_M3(unsigned char *str)
{
    int             adj;
    int             i;
    unsigned char  *src, *dst;
    unsigned char   buf[512];
    unsigned char   charset[512], dst1[512];


    src = str;
    dst = buf;
    adj = 0;

    while (*src && (dst - buf) < sizeof(buf) - 1) {
    if (*src != '=') {  /* Thor: not coded */
        unsigned char  *tmp = src;
        while (adj && *tmp && isspace(*tmp))
        tmp++;
        if (adj && *tmp == '=') {   /* Thor: jump over space */
        adj = 0;
        src = tmp;
        } else
        *dst++ = *src++;
        /* continue; *//* Thor: take out */
    } else {        /* Thor: *src == '=' */
        unsigned char  *tmp = src + 1;
        if (*tmp == '?') {  /* Thor: =? coded */
        /* "=?%s?Q?" for QP, "=?%s?B?" for BASE64 */
        tmp++;
        i = 0;
        while (*tmp && *tmp != '?') {
            if (i + 1 < sizeof(charset)) {
            charset[i] = *tmp;
            charset[i + 1] = '\0';
            i++;
            }
            tmp++;
        }
        if (*tmp && tmp[1] && tmp[2] == '?') {  /* Thor: *tmp == '?' */
#ifdef USE_ICONV
            int             i = mmdecode(tmp + 3, tmp[1], dst1);
            i = str_iconv(charset, "big5", dst1, i, dst,
                  sizeof(buf) - ((int)(dst - buf)));
#else
            int             i = mmdecode(tmp + 3, tmp[1], dst);
#endif
            if (i >= 0) {
            tmp += 3;   /* Thor: decode's src */
#if 0
            while (*tmp++ != '?');  /* Thor: no ? end, mmdecode
                         * -1 */
#endif
            while (*tmp && *tmp++ != '?');  /* Thor: no ? end,
                             * mmdecode -1 */
            /* Thor.980901: 0 也算 decode 結束 */
            if (*tmp == '=')
                tmp++;
            src = tmp;  /* Thor: decode over */
            dst += i;
            adj = 1;/* Thor: adjcent */
            }
        }
        }
        while (src != tmp)  /* Thor: not coded */
        *dst++ = *src++;
    }
    }
    *dst = 0;
    strcpy(str, buf);
}