3 * fmt_rfc2047.c -- decode RFC-2047 header format
7 * This code is Copyright (c) 2002, by the authors of nmh. See the
8 * COPYRIGHT file in the root directory of the nmh distribution for
9 * complete copyright information.
19 static signed char hexindex[] = {
20 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
21 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
22 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
23 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
24 -1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
25 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
26 -1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
27 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
30 static signed char index_64[128] = {
31 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
32 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
33 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
34 52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
35 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11,12,13,14,
36 15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
37 -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
38 41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
41 #define char64(c) (((unsigned char) (c) > 127) ? -1 : index_64[(unsigned char) (c)])
44 unqp (unsigned char byte1, unsigned char byte2)
46 if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
48 return (hexindex[byte1] << 4 | hexindex[byte2]);
51 /* Check if character is linear whitespace */
52 #define is_lws(c) ((c) == ' ' || (c) == '\t' || (c) == '\n')
56 * Decode the string as a RFC-2047 header field
59 /* Add character to the destination buffer, and bomb out if it fills up */
60 #define ADDCHR(C) do { *q++ = (C); dstlen--; if (!dstlen) goto buffull; } while (0)
63 decode_rfc2047 (char *str, char *dst, size_t dstlen)
66 char *startofmime, *endofmime;
67 int c, quoted_printable;
68 int encoding_found = 0; /* did we decode anything? */
69 int between_encodings = 0; /* are we between two encodings? */
70 int equals_pending = 0; /* is there a '=' pending? */
71 int whitespace = 0; /* how much whitespace between encodings? */
73 int use_iconv = 0; /* are we converting encoding with iconv? */
76 char *saveq, *convbuf = NULL;
84 * Do a quick and dirty check for the '=' character.
85 * This should quickly eliminate many cases.
87 if (!strchr (str, '='))
90 for (p = str, q = dst; *p; p++) {
100 * If we had an '=' character pending from
101 * last iteration, then add it first.
103 if (equals_pending) {
106 between_encodings = 0; /* we have added non-whitespace text */
110 /* count linear whitespace while between encodings */
111 if (between_encodings && is_lws(*p))
114 between_encodings = 0; /* we have added non-whitespace text */
119 equals_pending = 1; /* we have a '=' pending */
121 /* Check for initial =? */
122 if (*p == '=' && p[1] && p[1] == '?' && p[2]) {
125 /* Scan ahead for the next '?' character */
126 for (pp = startofmime; *pp && *pp != '?'; pp++)
132 /* Check if character set can be handled natively */
133 if (!check_charset(startofmime, pp - startofmime)) {
135 /* .. it can't. We'll use iconv then. */
137 cd = iconv_open(get_charset(), startofmime);
138 fromutf8 = !mh_strcasecmp(startofmime, "UTF-8");
140 if (cd == (iconv_t)-1) continue;
147 startofmime = pp + 1;
149 /* Check for valid encoding type */
150 if (*startofmime != 'B' && *startofmime != 'b' &&
151 *startofmime != 'Q' && *startofmime != 'q')
154 /* Is encoding quoted printable or base64? */
155 quoted_printable = (*startofmime == 'Q' || *startofmime == 'q');
158 /* Check for next '?' character */
159 if (*startofmime != '?')
164 * Scan ahead for the ending ?=
166 * While doing this, we will also check if encoded
167 * word has any embedded linear whitespace.
170 for (pp = startofmime; *pp && *(pp+1); pp++) {
173 } else if (*pp == '?' && pp[1] == '=') {
178 if (is_lws(*pp) || endofmime == NULL)
182 * We've found an encoded word, so we can drop
183 * the '=' that was pending
188 * If we are between two encoded words separated only by
189 * linear whitespace, then we ignore the whitespace.
190 * We will roll back the buffer the number of whitespace
191 * characters we've seen since last encoded word.
193 if (between_encodings) {
195 dstlen += whitespace;
200 * empty encoded text. This ensures that we don't
201 * malloc 0 bytes but skip on to the end
203 if (endofmime == startofmime && use_iconv) {
211 q = convbuf = (char *) mh_xmalloc(endofmime - startofmime);
213 /* ADDCHR2 is for adding characters when q is or might be convbuf:
214 * in this case on buffer-full we want to run iconv before returning.
215 * I apologise for the dreadful name.
217 #define ADDCHR2(C) do { *q++ = (C); dstlen--; if (!dstlen) goto iconvbuffull; } while (0)
219 #define ADDCHR2(C) ADDCHR(C)
222 /* Now decode the text */
223 if (quoted_printable) {
224 for (pp = startofmime; pp < endofmime; pp++) {
226 c = unqp (pp[1], pp[2]);
232 } else if (*pp == '_') {
243 while (pp < endofmime) {
245 while ((pp < endofmime) &&
246 ((c1 = char64(*pp)) == -1)) {
249 if (pp < endofmime) {
252 while ((pp < endofmime) &&
253 ((c2 = char64(*pp)) == -1)) {
256 if (pp < endofmime && c1 != -1 && c2 != -1) {
257 ADDCHR2((c1 << 2) | (c2 >> 4));
261 while ((pp < endofmime) &&
262 ((c3 = char64(*pp)) == -1)) {
265 if (pp < endofmime && c2 != -1 && c3 != -1) {
266 ADDCHR2(((c2 & 0xF) << 4) | (c3 >> 2));
270 while ((pp < endofmime) &&
271 ((c4 = char64(*pp)) == -1)) {
274 if (pp < endofmime && c3 != -1 && c4 != -1) {
275 ADDCHR2(((c3 & 0x3) << 6) | (c4));
283 /* NB that the string at convbuf is not necessarily NUL terminated here:
284 * q points to the first byte after the valid part.
286 /* Convert to native character set */
288 size_t inbytes = q - convbuf;
289 ICONV_CONST char *start = convbuf;
292 if (iconv(cd, &start, &inbytes, &saveq, &savedstlen) ==
294 if (errno != EILSEQ) break;
295 /* character couldn't be converted. we output a `?'
296 * and try to carry on which won't work if
297 * either encoding was stateful */
298 iconv (cd, 0, 0, &saveq, &savedstlen);
305 /* skip to next input character */
307 for (start++;(start < q) && ((*start & 192) == 128);start++)
316 /* Stop now if (1) we hit the end of the buffer trying to do
317 * MIME decoding and have just iconv-converted a partial string
318 * or (2) our iconv-conversion hit the end of the buffer.
320 if (!dstlen || !savedstlen)
328 * Now that we are done decoding this particular
329 * encoded word, advance string to trailing '='.
333 encoding_found = 1; /* we found (at least 1) encoded word */
334 between_encodings = 1; /* we have just decoded something */
335 whitespace = 0; /* re-initialize amount of whitespace */
339 if (use_iconv) iconv_close(cd);
342 /* If an equals was pending at end of string, add it now. */
347 return encoding_found;
350 /* q is currently just off the end of the buffer, so rewind to NUL terminate */
353 return encoding_found;