* Update to reflect the change from alpine.x10host.com to alpineapp.email.

[alpine.git] / pith / charset.c

/*
 * ========================================================================
 * Copyright 2013-2022 Eduardo Chappa
 * Copyright 2006-2008 University of Washington
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * ========================================================================
 */

#include "../pith/headers.h"
#include "../pith/charset.h"
#include "../pith/state.h"
#include "../pith/conf.h"
#include "../pith/escapes.h"
#include "../pith/mimedesc.h"
#include "../pith/filter.h"
#include "../pith/string.h"
#include "../pith/options.h"


/*
 * Internal prototypes
 */
int            rfc1522_token(char *, int (*)(int), char *, char **);
int            rfc1522_valtok(int);
int            rfc1522_valenc(int);
int            rfc1522_valid(char *, char **, char **, char **, char **);
void           rfc1522_copy_and_transliterate(unsigned char *, unsigned char **, size_t,
                                              unsigned char *, unsigned long, char *);
unsigned char *rfc1522_encoded_word(unsigned char *, int, char *);
char          *rfc1522_8bit(void *, int);
char          *rfc1522_binary(void *, int);


char *
body_charset(MAILSTREAM *stream, long int msgno, unsigned char *section)
{
    BODY *body;
    char *charset;


    if((body = mail_body(stream, msgno, section)) && body->type == TYPETEXT){
        if(!(charset = parameter_val(body->parameter, "charset")))
          charset = cpystr("US-ASCII");

        return(charset);
    }

    return(NULL);
}


/*
 * Copies the source string into allocated space with the 8-bit EUC codes
 * (on Unix) or the Shift-JIS (on PC) converted into ISO-2022-JP.
 * Caller is responsible for freeing the result.
 */
unsigned char *
trans_euc_to_2022_jp(unsigned char *src)
{
    size_t len, alloc;
    unsigned char *rv, *p, *q;
    int    inside_esc_seq = 0;
    int    c1 = -1;             /* remembers first of pair for Shift-JIS */

    if(!src)
      return(NULL);

    len = strlen((char *) src);

    /*
     * Worst possible increase is every other character an 8-bit character.
     * In that case, each of those gets 6 extra characters for the escape
     * sequences. We're not too concerned about the extra length because
     * these are relatively short strings.
     */
    alloc = len + 1 + ((len+1)/2) * 6;
    rv = (unsigned char *) fs_get(alloc * sizeof(char));

    for(p = src, q = rv; *p; p++){
        if(inside_esc_seq){
            if(c1 >= 0){                        /* second of a pair? */
                int adjust = *p < 159;
                int rowOffset = c1 < 160 ? 112 : 176;
                int cellOffset = adjust ? (*p > 127 ? 32 : 31) : 126;

                *q++ = ((c1 - rowOffset) << 1) - adjust;
                *q++ = *p - cellOffset;
                c1 = -1;
            }
            else if(*p & 0x80){
                *q++ = (*p & 0x7f);
            }
            else{
                *q++ = '\033';
                *q++ = '(';
                *q++ = 'B';
                *q++ = (*p);
                c1 = -1;
                inside_esc_seq = 0;
            }
        }
        else{
            if(*p & 0x80){
                *q++ = '\033';
                *q++ = '$';
                *q++ = 'B';
                *q++ = (*p & 0x7f);
                inside_esc_seq = 1;
            }
            else{
                *q++ = (*p);
            }
        }
    }

    if(inside_esc_seq){
        *q++ = '\033';
        *q++ = '(';
        *q++ = 'B';
    }

    *q = '\0';

    return(rv);
}


/*
 *  * * * * * * * *      RFC 1522 support routines      * * * * * * * *
 *
 *   RFC 1522 support is *very* loosely based on code contributed
 *   by Lars-Erik Johansson <lej@cdg.chalmers.se>.  Thanks to Lars-Erik,
 *   and apologies for taking such liberties with his code.
 */

#define RFC1522_INIT    "=?"
#define RFC1522_INIT_L  2
#define RFC1522_TERM    "?="
#define RFC1522_TERM_L  2
#define RFC1522_DLIM    "?"
#define RFC1522_DLIM_L  1
#define RFC1522_MAXW    75      /* RFC's say 75, but no senders seem to care*/
#define ESPECIALS       "()<>@,;:\"/[]?.="
#define RFC1522_OVERHEAD(S)     (RFC1522_INIT_L + RFC1522_TERM_L +      \
                                 (2 * RFC1522_DLIM_L) + strlen(S) + 1);
#define RFC1522_ENC_CHAR(C)     (((C) & 0x80) || !rfc1522_valtok(C)     \
                                 || (C) == '_' )

/*
 * rfc1522_decode_to_utf8 - try to decode the given source string ala RFC 2047
 *                  (obsoleted RFC 1522) into the given destination buffer,
 *                  encoded in UTF-8.
 *
 * How large should d be? The decoded string of octets will fit in
 * the same size string as the source string. However, because we're
 * translating that into UTF-8 the result may expand. Currently the
 * Thai character set has single octet characters which expand to
 * three octets in UTF-8. So it would be safe to use 3 * strlen(s)
 * for the size of d. One can imagine a currently non-existent
 * character set that expanded to 4 octets instead, so use 4 to be
 * super safe.
 *
 * Returns: pointer to either the destination buffer containing the
 *          decoded text, or a pointer to the source buffer if there was
 *          no valid 'encoded-word' found during scanning.
 */
unsigned char *
rfc1522_decode_to_utf8(unsigned char *d, size_t len, char *s)
{
    unsigned char *rv = NULL, *p;
    char          *start = s, *sw, *enc, *txt, *ew, **q, *lang;
    char          *cset;
    unsigned long  l;
    int            i;

    *d = '\0';                                  /* init destination */

    while(s && (sw = strstr(s, RFC1522_INIT))){
        if(!rv)  /* there's something to do, init it */
          rv = d;
        /* validate the rest of the encoded-word */
        if(rfc1522_valid(sw, &cset, &enc, &txt, &ew)){
            /*
             * We may have been putting off copying the first part of the
             * source while waiting to see if we have to copy at all.
             */
            if(rv == d && s != start){
                rfc1522_copy_and_transliterate(rv, &d, len, (unsigned char *) start,
                                               sw - start, NULL);
                s = sw;
            }

            /* copy everything between s and sw to destination */
            for(i = 0; &s[i] < sw; i++)
              if(!isspace((unsigned char)s[i])){ /* if some non-whitespace */
                  while(s < sw && d-rv<len-1)
                    *d++ = (unsigned char) *s++;

                  break;
              }

            enc[-1] = txt[-1] = ew[0] = '\0';   /* tie off token strings */

            if((lang = strchr(cset, '*')) != NULL)
              *lang++ = '\0';

            /* based on encoding, write the encoded text to output buffer */
            switch(*enc){
              case 'Q' :                        /* 'Q' encoding */
              case 'q' :
                /* special hocus-pocus to deal with '_' exception, too bad */
                for(l = 0L, i = 0; txt[l]; l++)
                  if(txt[l] == '_')
                    i++;

                if(i){
                    q = (char **) fs_get((i + 1) * sizeof(char *));
                    for(l = 0L, i = 0; txt[l]; l++)
                      if(txt[l] == '_'){
                          q[i++] = &txt[l];
                          txt[l] = SPACE;
                      }

                    q[i] = NULL;
                }
                else
                  q = NULL;

                if((p = rfc822_qprint((unsigned char *)txt, strlen(txt), &l)) != NULL){
                    rfc1522_copy_and_transliterate(rv, &d, len, p, l, cset);
                    fs_give((void **)&p);       /* free encoded buf */
                }
                else{
                    if(q)
                      fs_give((void **) &q);

                    goto bogus;
                }

                if(q){                          /* restore underscores */
                    for(i = 0; q[i]; i++)
                      *(q[i]) = '_';

                    fs_give((void **)&q);
                }

                break;

              case 'B' :                        /* 'B' encoding */
              case 'b' :
                if((p = rfc822_base64((unsigned char *) txt, strlen(txt), &l)) != NULL){
                    rfc1522_copy_and_transliterate(rv, &d, len, p, l, cset);
                    fs_give((void **)&p);       /* free encoded buf */
                }
                else
                  goto bogus;

                break;

              default:
                rfc1522_copy_and_transliterate(rv, &d, len, (unsigned char *) txt,
                                               strlen(txt), NULL);
                dprint((1, "RFC1522_decode: Unknown ENCODING: %s\n",
                       enc ? enc : "?"));
                break;
            }

            /* restore trompled source string */
            enc[-1] = txt[-1] = '?';
            ew[0]   = RFC1522_TERM[0];

            /* advance s to start of text after encoded-word */
            s = ew + RFC1522_TERM_L;

            if(lang)
              lang[-1] = '*';
        }
        else{
            /*
             * Found intro, but bogus data followed, treat it as normal text.
             */
            l = (sw - s) + RFC1522_INIT_L;
            rfc1522_copy_and_transliterate(rv, &d, len, (unsigned char *) s, l, NULL);
            for(; isspace((unsigned char) *(s+l)) && d-rv<len-1;l++)
                *d++ = *(s+l);  /* copy any trailing space */
            rv[len-1] = '\0';
            *d = '\0';
            s += l;
        }
    }

    if(rv){
        if(s && *s){                            /* copy remaining text */
            rfc1522_copy_and_transliterate(rv, &d, len, (unsigned char *) s, strlen(s), NULL);
            rv[len-1] = '\0';
        }
    }
    else if(s){
        rv = d;
        rfc1522_copy_and_transliterate(rv, &d, len, (unsigned char *) s, strlen(s), NULL);
        rv[len-1] = '\0';
    }

    return(rv ? rv : (unsigned char *) start);

  bogus:
    dprint((1, "RFC1522_decode: BOGUS INPUT: -->%s<--\n",
           start ? start : "?"));
    return((unsigned char *) start);
}


/*
 * rfc1522_token - scan the given source line up to the end_str making
 *                 sure all subsequent chars are "valid" leaving endp
 *                 a the start of the end_str.
 * Returns: TRUE if we got a valid token, FALSE otherwise
 */
int
rfc1522_token(char *s, int (*valid) (int), char *end_str, char **endp)
{
    while(*s){
        if((char) *s == *end_str                /* test for matching end_str */
           && ((end_str[1])
                ? !strncmp((char *)s + 1, end_str + 1, strlen(end_str + 1))
                : 1)){
            *endp = s;
            return(TRUE);
        }

        if(!(*valid)(*s++))                     /* test for valid char */
          break;
    }

    return(FALSE);
}


/*
 * rfc1522_valtok - test for valid character in the RFC 1522 encoded
 *                  word's charset and encoding fields.
 */
int
rfc1522_valtok(int c)
{
    return(!(c == SPACE || iscntrl(c & 0x7f) || strindex(ESPECIALS, c)));
}


/*
 * rfc1522_valenc - test for valid character in the RFC 1522 encoded
 *                  word's encoded-text field.
 */
int
rfc1522_valenc(int c)
{
    return(!(c == '?' || c == SPACE) && isprint((unsigned char)c));
}


/*
 * rfc1522_valid - validate the given string as to it's rfc1522-ness
 */
int
rfc1522_valid(char *s, char **charset, char **enc, char **txt, char **endp)
{
    char *c, *e, *t, *p;
    int   rv;

    rv = rfc1522_token(c = s+RFC1522_INIT_L, rfc1522_valtok, RFC1522_DLIM, &e)
           && rfc1522_token(++e, rfc1522_valtok, RFC1522_DLIM, &t)
           && rfc1522_token(++t, rfc1522_valenc, RFC1522_TERM, &p);

    if(charset)
      *charset = c;

    if(enc)
      *enc = e;

    if(txt)
      *txt = t;

    if(endp)
      *endp = p;

    return(rv);
}


/*
 * rfc1522_copy_and_transliterate - copy given buf to destination buffer
 *                                  as UTF-8 characters
 */
void
rfc1522_copy_and_transliterate(unsigned char  *rv,
                               unsigned char **d,
                               size_t          len,
                               unsigned char  *s,
                               unsigned long   l,
                               char           *cset)
{
    unsigned long i;
    SIZEDTEXT     src, xsrc;

    src.data = s;
    src.size = l;
    memset(&xsrc, 0, sizeof(SIZEDTEXT));

    /* transliterate decoded segment to utf-8 */
    if(cset){
        if(strucmp((char *) cset, "us-ascii")
           && strucmp((char *) cset, "utf-8")){
            if(utf8_charset(cset)){
                if(!utf8_text(&src, cset, &xsrc, 0L)){
                    /* should not happen */
                    alpine_panic("c-client failed to transliterate recognized characterset");
                }
            }
            else{
                /* non-xlatable charset */
                for(i = 0; i < l; i++)
                  if(src.data[i] & 0x80){
                      xsrc.data = (unsigned char *) fs_get((l+1) * sizeof(unsigned char));
                      xsrc.size = l;
                      for(i = 0; i < l; i++)
                        xsrc.data[i] = (src.data[i] & 0x80) ? '?' : src.data[i];

                      break;
                  }
            }
        }
    }
    else{
        const CHARSET *cs;

        src.data = s;
        src.size = strlen((char *) s);

        if((cs = utf8_infercharset(&src))){
            if(!(cs->type == CT_ASCII || cs->type == CT_UTF8)){
                if(!utf8_text_cs(&src, cs, &xsrc, 0L, 0L)){
                    /* should not happen */
                    alpine_panic("c-client failed to transliterate recognized characterset");
                }
            }
        }
        else if((cset=ps_global->VAR_UNK_CHAR_SET)
                && strucmp((char *) cset, "us-ascii")
                && strucmp((char *) cset, "utf-8")
                && utf8_charset(cset)){
                if(!utf8_text(&src, cset, &xsrc, 0L)){
                    /* should not happen */
                    alpine_panic("c-client failed to transliterate recognized character set");
                }
        }
        else{
            /* unknown bytes - mask off high bit chars */
            for(i = 0; i < l; i++)
              if(src.data[i] & 0x80){
                  xsrc.data = (unsigned char *) fs_get((l+1) * sizeof(unsigned char));
                  xsrc.size = l;
                  for(i = 0; i < l; i++)
                    xsrc.data[i] = (src.data[i] & 0x80) ? '?' : src.data[i];

                  break;
              }
        }
    }

    if(xsrc.data){
        s = xsrc.data;
        l = xsrc.size;
    }

    i = MIN(l,len-1-((*d)-rv));
    strncpy((char *) (*d), (char *) s, i);
    (*d)[i] = '\0';
    *d += l;                    /* advance dest ptr to EOL */
    if((*d)-rv > len-1)
      *d = rv+len-1;

    if(xsrc.data && src.data != xsrc.data)
      fs_give((void **) &xsrc.data);
}



/*
 * rfc1522_encode - encode the given source string ala RFC 1522,
 *                  IF NECESSARY, into the given destination buffer.
 *                  Don't bother copying if it turns out encoding
 *                  isn't necessary.
 *
 * Returns: pointer to either the destination buffer containing the
 *          encoded text, or a pointer to the source buffer if we didn't
 *          have to encode anything.
 */
char *
rfc1522_encode(char *d, size_t dlen, unsigned char *s, char *charset)
{
    unsigned char *p, *q;
    int            n;

    if(!s)
      return((char *) s);

    if(!charset)
      charset = UNKNOWN_CHARSET;

    /* look for a reason to encode */
    for(p = s, n = 0; *p; p++)
      if((*p) & 0x80){
          n++;
      }
      else if(*p == RFC1522_INIT[0]
              && !strncmp((char *) p, RFC1522_INIT, RFC1522_INIT_L)){
          if(rfc1522_valid((char *) p, NULL, NULL, NULL, (char **) &q))
            p = q + RFC1522_TERM_L - 1;         /* advance past encoded gunk */
      }
      else if(*p == ESCAPE && match_escapes((char *)(p+1))){
          n++;
      }

    if(n){                                      /* found, encoding to do */
        char *rv  = d, *t,
              enc = (n > (2 * (p - s)) / 3) ? 'B' : 'Q';

        while(*s){
            if(d-rv < dlen-1-(RFC1522_INIT_L+2*RFC1522_DLIM_L+1)){
                sstrncpy(&d, RFC1522_INIT, dlen-(d-rv));        /* insert intro header, */
                sstrncpy(&d, charset, dlen-(d-rv));             /* character set tag, */
                sstrncpy(&d, RFC1522_DLIM, dlen-(d-rv));        /* and encoding flavor */
                if(dlen-(d-rv) > 0) 
                  *d++ = enc;

                sstrncpy(&d, RFC1522_DLIM, dlen-(d-rv));
            }

            /*
             * feed lines to encoder such that they're guaranteed
             * less than RFC1522_MAXW.
             */
            p = rfc1522_encoded_word(s, enc, charset);
            if(enc == 'B')                      /* insert encoded data */
              sstrncpy(&d, t = rfc1522_binary(s, p - s), dlen-1-(d-rv));
            else                                /* 'Q' encoding */
              sstrncpy(&d, t = rfc1522_8bit(s, p - s), dlen-1-(d-rv));

            sstrncpy(&d, RFC1522_TERM, dlen-1-(d-rv));  /* insert terminator */
            fs_give((void **) &t);
            if(*p)                              /* more src string follows */
              sstrncpy(&d, "\015\012 ", dlen-1-(d-rv)); /* insert cont. line */

            s = p;                              /* advance s */
        }

        rv[dlen-1] = '\0';
        return(rv);
    }
    else
      return((char *) s);                       /* no work for us here */
}



/*
 * rfc1522_encoded_word -- cut given string into max length encoded word
 *
 * Return: pointer into 's' such that the encoded 's' is no greater
 *         than RFC1522_MAXW
 *
 *  NOTE: this line break code is NOT cognizant of any SI/SO
 *  charset requirements nor similar strategies using escape
 *  codes.  Hopefully this will matter little and such
 *  representation strategies don't also include 8bit chars.
 */
unsigned char *
rfc1522_encoded_word(unsigned char *s, int enc, char *charset)
{
    int goal = RFC1522_MAXW - RFC1522_OVERHEAD(charset);

    if(enc == 'B')                      /* base64 encode */
      for(goal = ((goal / 4) * 3) - 2; goal && *s; goal--, s++)
        ;
    else                                /* special 'Q' encoding */
      if(!strucmp(charset, "UTF-8")){   /* special handling for utf-8 */
        int i,more;
        unsigned char *p;
        for(; goal && *s; s++){
           more = *s < 0x80 ? 0
                   : *s < 0xe0 ? 1
                   : *s < 0xf0 ? 2
                   : *s < 0xf8 ? 3
                   : *s < 0xfc ? 4
                   : *s < 0xfe ? 5 : -1;
           if(more >= 0){       /* check that we have at least more characters */
                for(p = s, i = 0; i <= more && *p != '\0'; i++, p++)
                    goal -= RFC1522_ENC_CHAR(*p) ? 3 : 1;
                if(goal < 0)   /* does not fit in encoded word */
                   break;
                s += i - 1;     /* i - 1 should be equal to more */
           }
           else /* encode it, and skip it */
              if((goal -= RFC1522_ENC_CHAR(*s) ? 3 : 1) < 0)
                break;
        }
      }
      else
        for(; goal && *s; s++)
          if((goal -= RFC1522_ENC_CHAR(*s) ? 3 : 1) < 0)
            break;

    return(s);
}



/*
 * rfc1522_8bit -- apply RFC 1522 'Q' encoding to the given 8bit buffer
 *
 * Return: alloc'd buffer containing encoded string
 */
char *
rfc1522_8bit(void *src, int slen)
{
    char *ret = (char *) fs_get ((size_t) (3*slen + 2));
    char *d = ret;
    unsigned char c;
    unsigned char *s = (unsigned char *) src;

    while (slen--) {                            /* for each character */
        if (((c = *s++) == '\015') && (*s == '\012') && slen) {
            *d++ = '\015';                      /* true line break */
            *d++ = *s++;
            slen--;
        }
        else if(c == SPACE){                    /* special encoding case */
            *d++ = '_';
        }
        else if(RFC1522_ENC_CHAR(c)){
            *d++ = '=';                         /* quote character */
            C2XPAIR(c, d);
        }
        else
          *d++ = (char) c;                      /* ordinary character */
    }

    *d = '\0';                                  /* tie off destination */
    return(ret);
}


/*
 * rfc1522_binary -- apply RFC 1522 'B' encoding to the given 8bit buffer
 *
 * Return: alloc'd buffer containing encoded string
 */
char *
rfc1522_binary (void *src, int srcl)
{
    static char *v =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    unsigned char *s = (unsigned char *) src;
    char *ret, *d;

    d = ret = (char *) fs_get ((size_t) ((((srcl + 2) / 3) * 4) + 1));
    for (; srcl; s += 3) {      /* process tuplets */
                                /* byte 1: high 6 bits (1) */
        *d++ = v[s[0] >> 2];
                                /* byte 2: low 2 bits (1), high 4 bits (2) */
        *d++ = v[((s[0] << 4) + (--srcl ? (s[1] >> 4) : 0)) & 0x3f];
                                /* byte 3: low 4 bits (2), high 2 bits (3) */
        *d++ = srcl ? v[((s[1] << 2) + (--srcl ? (s[2] >> 6) :0)) & 0x3f] :'=';
                                /* byte 4: low 6 bits (3) */
        *d++ = srcl ? v[s[2] & 0x3f] : '=';
        if(srcl)
          srcl--;               /* count third character if processed */
    }

    *d = '\0';                  /* tie off string */
    return(ret);                /* return the resulting string */
}


/*
 * Checks if charset conversion is possible and which quality could be achieved
 *
 * args: from_cs -- charset to convert from
 *       to_cs   -- charset to convert to
 *
 * Results:
 * CONV_TABLE->table   -- conversion table, NULL if conversion not needed
 *                        or not supported
 * CONV_TABLE->quality -- conversion quality (conversion not supported, not
 *                        needed, loses special chars, or loses letters
 *
 * The other entries of CONV_TABLE are used inside this function only
 * and may not be used outside unless this documentation is updated.
 */
CONV_TABLE *
conversion_table(char *from_cs, char *to_cs)
{
    int               i, j;
    unsigned char    *p = NULL;
    unsigned short   *fromtab, *totab;
    CONV_TABLE       *ct = NULL;
    const CHARSET    *from, *to;
    static CONV_TABLE null_tab;

    if(!(from_cs && *from_cs && to_cs && *to_cs) || !strucmp(from_cs, to_cs)){
        memset(&null_tab, 0, sizeof(null_tab));
        null_tab.quality = CV_NO_TRANSLATE_NEEDED;
        return(&null_tab);
    }

    /*
     * First check to see if we are already set up for this pair of charsets.
     */
    if((ct = ps_global->conv_table) != NULL
       && ct->from_charset && ct->to_charset
       && !strucmp(ct->from_charset, from_cs)
       && !strucmp(ct->to_charset, to_cs))
      return(ct);

    /*
     * No such luck. Get rid of the cache of the previous translation table
     * and build a new one.
     */
    if(ct){
        if(ct->table && (ct->convert != gf_convert_utf8_charset))
          fs_give((void **) &ct->table);
        
        if(ct->from_charset)
          fs_give((void **) &ct->from_charset);
        
        if(ct->to_charset)
          fs_give((void **) &ct->to_charset);
    }
    else
      ct = ps_global->conv_table = (CONV_TABLE *) fs_get(sizeof(*ct));
    
    memset(ct, 0, sizeof(*ct));

    ct->from_charset = cpystr(from_cs);
    ct->to_charset   = cpystr(to_cs);
    ct->quality = CV_NO_TRANSLATE_POSSIBLE;

    /*
     * Check to see if a translation is feasible.
     */
    from = utf8_charset(from_cs);
    to =   utf8_charset(to_cs);

    if(from && to){             /* if both charsets found */
                                /* no mapping if same or from is ASCII */
        if((from->type == to->type && from->tab == to->tab)
           || (from->type == CT_ASCII))
            ct->quality = CV_NO_TRANSLATE_NEEDED;
        else switch(from->type){
        case CT_1BYTE0:         /* 1 byte no table */
        case CT_1BYTE:          /* 1 byte ASCII + table 0x80-0xff */
        case CT_1BYTE8:         /* 1 byte table 0x00 - 0xff */
            switch(to->type){
            case CT_1BYTE0:     /* 1 byte no table */
            case CT_1BYTE:      /* 1 byte ASCII + table 0x80-0xff */
            case CT_1BYTE8:     /* 1 byte table 0x00 - 0xff */
                ct->quality = (from->script & to->script) ?
                  CV_LOSES_SOME_LETTERS : CV_LOSES_SPECIAL_CHARS;
                break;
            }
            break;
        case CT_UTF8:           /* variable UTF-8 encoded Unicode no table */
        /* If source is UTF-8, see if destination charset has an 8 or 16 bit
         * coded character set that we can translate to.  By special
         * dispensation, kludge ISO-2022-JP to EUC or Shift-JIS, but don't
         * try to do any other ISO 2022 charsets or UTF-7.
         */
            switch (to->type){
            case CT_SJIS:       /* 2 byte Shift-JIS */
                                /* only win if can get EUC-JP chartab */
                if(utf8_charset("EUC-JP"))
                    ct->quality = CV_LOSES_SOME_LETTERS;
                break;
            case CT_ASCII:      /* 7-bit ASCII no table */
            case CT_1BYTE0:     /* 1 byte no table */
            case CT_1BYTE:      /* 1 byte ASCII + table 0x80-0xff */
            case CT_1BYTE8:     /* 1 byte table 0x00 - 0xff */
            case CT_EUC:        /* 2 byte ASCII + utf8_eucparam base/CS2/CS3 */
            case CT_DBYTE:      /* 2 byte ASCII + utf8_eucparam */
            case CT_DBYTE2:     /* 2 byte ASCII + utf8_eucparam plane1/2 */
                ct->quality = CV_LOSES_SOME_LETTERS;
                break;
            }
            break;
        }

        switch (ct->quality) {  /* need to map? */
        case CV_NO_TRANSLATE_POSSIBLE:
        case CV_NO_TRANSLATE_NEEDED:
          break;                /* no mapping needed */
        default:                /* do mapping */
            switch (from->type) {
            case CT_UTF8:       /* UTF-8 to legacy character set */
              if((ct->table = utf8_rmap (to_cs)) != NULL)
                ct->convert = gf_convert_utf8_charset;
              break;

            case CT_1BYTE0:     /* ISO 8859-1 */
            case CT_1BYTE:      /* low part ASCII, high part other */
            case CT_1BYTE8:     /* low part has some non-ASCII */
            /*
             * The fromtab and totab tables are mappings from the 128 character
             * positions 128-255 to their Unicode values (so unsigned shorts).
             * The table we are creating is such that if
             *
             *    from_char_value -> unicode_value
             *    to_char_value   -> same_unicode_value
             *
             *  then we want to map from_char_value -> to_char_value
             *
             * To simplify conversions we create the whole 256 element array,
             * with the first 128 positions just the identity. If there is no
             * conversion for a particular from_char_value (that is, no
             * to_char_value maps to the same unicode character) then we put
             *  '?' in that character. We may want to output blob on the PC,
             * but don't so far.
             *
             * If fromtab or totab are NULL, that means the mapping is simply
             * the identity mapping. Since that is still useful to us, we
             * create it on the fly.
             */
                fromtab = (unsigned short *) from->tab;
                totab   = (unsigned short *) to->tab;

                ct->convert = gf_convert_8bit_charset;
                p = ct->table = (unsigned char *)
                  fs_get(256 * sizeof(unsigned char));
                for(i = 0; i < 256; i++){
                    unsigned int fc = 0;
                    p[i] = '?';
                    switch(from->type){ /* get "from" UCS-2 codepoint */
                    case CT_1BYTE0:     /* ISO 8859-1 */
                        fc = i;
                        break;
                    case CT_1BYTE:      /* low part ASCII, high part other */
                        fc = (i < 128) ? i : fromtab[i-128];
                        break;
                    case CT_1BYTE8:     /* low part has some non-ASCII */
                        fc = fromtab[i];
                        break;
                    }
                    switch(to->type){ /* match against "to" UCS-2 codepoint */
                    case CT_1BYTE0: /* identity match for ISO 8859-1*/
                        if(fc < 256)
                          p[i] = fc;
                        break;
                    case CT_1BYTE: /* ASCII is identity, search high part */
                        if(fc < 128) p[i] = fc;
                        else for(j = 0; j < 128; j++){
                            if(fc == totab[j]){
                                p[i] = 128 + j;
                                break;
                            }
                        }
                        break;
                    case CT_1BYTE8: /* search all codepoints */
                        for(j = 0; j < 256; j++){
                            if(fc == totab[j]){
                              p[i] = j;
                              break;
                            }
                        }
                        break;
                    }
                }
                break;
            }
        }
    }

    return(ct);
}


/*
 * Replace personal names in list of addresses with
 * decoded personal names in UTF-8.
 * Assumes we can free and reallocate the name.
 */
void
decode_addr_names_to_utf8(struct mail_address *a)
{
    for(; a; a = a->next)
      if(a->personal)
        convert_possibly_encoded_str_to_utf8(&a->personal);
}


/*
 * Strp is a pointer to an allocated string.
 * This routine will convert the string to UTF-8, possibly
 * freeing and re-allocating it.
 * The source string may or may not have RFC1522 encoding
 * which will be undone using rfc1522_decode.
 * The string will have been converted on return.
 */
void
convert_possibly_encoded_str_to_utf8(char **strp)
{
    size_t     len, lensrc, lenresult;
    char      *bufp, *decoded;

    if(!strp || !*strp || **strp == '\0')
      return;

    len = 4 * strlen(*strp) + 1;
    bufp = (char *) fs_get(len);

    decoded = (char *) rfc1522_decode_to_utf8((unsigned char *) bufp, len, *strp);
    if(decoded != (*strp)){     /* unchanged */
        if((lensrc=strlen(*strp)) >= (lenresult=strlen(decoded))){
            strncpy(*strp, decoded, lensrc);
            (*strp)[lensrc] = '\0';
        }
        else{
            fs_give((void **) strp);
            if(decoded == bufp){        /* this will be true */
                fs_resize((void **) &bufp, lenresult+1);
                *strp = bufp;
                bufp = NULL;
            }
            else{                       /* this is unreachable */
                *strp = cpystr(decoded);
            }
        }
    }
    /* else, already UTF-8 */

    if(bufp)
      fs_give((void **) &bufp);
}