xref: /plan9-contrib/sys/src/cmd/ip/imap4d/msg.c (revision ec59a3ddbfceee0efe34584c2c9981a5e5ff1ec4)
1 #include <u.h>
2 #include <libc.h>
3 #include <bio.h>
4 #include <libsec.h>
5 #include <auth.h>
6 #include <fcall.h>
7 #include "imap4d.h"
8 
9 static void	body64(int in, int out);
10 static void	bodystrip(int in, int out);
11 static void	cleanupHeader(Header *h);
12 static char	*domBang(char *s);
13 static void	freeMAddr(MAddr *a);
14 static void	freeMimeHdr(MimeHdr *mh);
15 static char	*headAddrSpec(char *e, char *w);
16 static MAddr	*headAddresses(void);
17 static MAddr	*headAddress(void);
18 static char	*headAtom(char *disallowed);
19 static int	headChar(int eat);
20 static char	*headDomain(char *e);
21 static MAddr	*headMAddr(MAddr *old);
22 static char	*headPhrase(char *e, char *w);
23 static char	*headQuoted(int start, int stop);
24 static char	*headSkipWhite(int);
25 static void	headSkip(void);
26 static char	*headSubDomain(void);
27 static char	*headText(void);
28 static void	headToEnd(void);
29 static char	*headWord(void);
30 static void	mimeDescription(Header *h);
31 static void	mimeDisposition(Header *h);
32 static void	mimeEncoding(Header *h);
33 static void	mimeId(Header *h);
34 static void	mimeLanguage(Header *h);
35 static void	mimeMd5(Header *h);
36 static MimeHdr	*mimeParams(void);
37 static void	mimeType(Header *h);
38 static MimeHdr	*mkMimeHdr(char *s, char *t, MimeHdr *next);
39 static void	msgAddDate(Msg *m);
40 static void	msgAddHead(Msg *m, char *head, char *body);
41 static int	msgBodySize(Msg *m);
42 static int	msgHeader(Msg *m, Header *h, char *file);
43 static long	msgReadFile(Msg *m, char *file, char **ss);
44 static int	msgUnix(Msg *m, int top);
45 static void	stripQuotes(char *q);
46 static MAddr	*unixFrom(char *s);
47 
48 
49 static char bogusBody[] =
50 	"This message contains null characters, so it cannot be displayed correctly.\r\n"
51 	"Most likely you were sent a bogus message or a binary file.\r\n"
52 	"\r\n"
53 	"Each of the following attachments has a different version of the message.\r\n"
54 	"The first is inlined with all non-printable characters stripped.\r\n"
55 	"The second contains the message as it was stored in your mailbox.\r\n"
56 	"The third has the initial header stripped.\r\n";
57 
58 static char bogusMimeText[] =
59 	"Content-Disposition: inline\r\n"
60 	"Content-Type: text/plain; charset=\"US-ASCII\"\r\n"
61 	"Content-Transfer-Encoding: 7bit\r\n";
62 
63 static char bogusMimeBinary[] =
64 	"Content-Disposition: attachment\r\n"
65 	"Content-Type: application/octet-stream\r\n"
66 	"Content-Transfer-Encoding: base64\r\n";
67 
68 /*
69  * stop list for header fields
70  */
71 static char	*headFieldStop = ":";
72 static char	*mimeTokenStop = "()<>@,;:\\\"/[]?=";
73 static char	*headAtomStop = "()<>@,;:\\\".[]";
74 static uchar	*headStr;
75 static uchar	*lastWhite;
76 
77 long
78 selectFields(char *dst, long n, char *hdr, SList *fields, int matches)
79 {
80 	SList *f;
81 	uchar *start;
82 	char *s;
83 	long m, nf;
84 
85 	headStr = (uchar*)hdr;
86 	m = 0;
87 	for(;;){
88 		start = headStr;
89 		s = headAtom(headFieldStop);
90 		if(s == nil)
91 			break;
92 		headSkip();
93 		for(f = fields; f != nil; f = f->next){
94 			if(cistrcmp(s, f->s) == !matches){
95 				nf = headStr - start;
96 				if(m + nf > n)
97 					return 0;
98 				memmove(&dst[m], start, nf);
99 				m += nf;
100 			}
101 		}
102 		free(s);
103 	}
104 	if(m + 3 > n)
105 		return 0;
106 	dst[m++] = '\r';
107 	dst[m++] = '\n';
108 	dst[m] = '\0';
109 	return m;
110 }
111 
112 void
113 freeMsg(Msg *m)
114 {
115 	Msg *k, *last;
116 
117 	free(m->iBuf);
118 	freeMAddr(m->to);
119 	if(m->replyTo != m->from)
120 		freeMAddr(m->replyTo);
121 	if(m->sender != m->from)
122 		freeMAddr(m->sender);
123 	if(m->from != m->unixFrom)
124 		freeMAddr(m->from);
125 	freeMAddr(m->unixFrom);
126 	freeMAddr(m->cc);
127 	freeMAddr(m->bcc);
128 	free(m->unixDate);
129 	cleanupHeader(&m->head);
130 	cleanupHeader(&m->mime);
131 	for(k = m->kids; k != nil; ){
132 		last = k;
133 		k = k->next;
134 		freeMsg(last);
135 	}
136 	free(m);
137 }
138 
139 ulong
140 msgSize(Msg *m)
141 {
142 	return m->head.size + m->size;
143 }
144 
145 int
146 infoIsNil(char *s)
147 {
148 	return s == nil || s[0] == '\0';
149 }
150 
151 char*
152 maddrStr(MAddr *a)
153 {
154 	char *host, *addr;
155 	int n;
156 
157 	host = a->host;
158 	if(host == nil)
159 		host = "";
160 	n = strlen(a->box) + strlen(host) + 2;
161 	if(a->personal != nil)
162 		n += strlen(a->personal) + 3;
163 	addr = emalloc(n);
164 	if(a->personal != nil)
165 		snprint(addr, n, "%s <%s@%s>", a->personal, a->box, host);
166 	else
167 		snprint(addr, n, "%s@%s", a->box, host);
168 	return addr;
169 }
170 
171 /*
172  * return actual name of f in m's fs directory
173  * this is special cased when opening m/rawbody, m/mimeheader, or m/rawheader,
174  * if the message was corrupted.  in that case,
175  * a temporary file is made to hold the base64 encoding of m/raw.
176  */
177 int
178 msgFile(Msg *m, char *f)
179 {
180 	Msg *parent, *p;
181 	Dir d;
182 	Tm tm;
183 	char buf[64], nbuf[2];
184 	uchar dbuf[64];
185 	int i, n, fd, fd1, fd2;
186 
187 	if(!m->bogus
188 	|| strcmp(f, "") != 0 && strcmp(f, "rawbody") != 0
189 	&& strcmp(f, "rawheader") != 0 && strcmp(f, "mimeheader") != 0
190 	&& strcmp(f, "info") != 0 && strcmp(f, "unixheader") != 0){
191 		if(strlen(f) > MsgNameLen)
192 			bye("internal error: msgFile name too long");
193 		strcpy(m->efs, f);
194 		return cdOpen(m->fsDir, m->fs, OREAD);
195 	}
196 
197 	/*
198 	 * walk up the stupid runt message parts for non-multipart messages
199 	 */
200 	parent = m->parent;
201 	if(parent != nil && parent->parent != nil){
202 		m = parent;
203 		parent = m->parent;
204 	}
205 	p = m;
206 	if(parent != nil)
207 		p = parent;
208 
209 	if(strcmp(f, "info") == 0 || strcmp(f, "unixheader") == 0){
210 		strcpy(p->efs, f);
211 		return cdOpen(p->fsDir, p->fs, OREAD);
212 	}
213 
214 	fd = imapTmp();
215 	if(fd < 0)
216 		return -1;
217 
218 	/*
219 	 * craft the message parts for bogus messages
220 	 */
221 	if(strcmp(f, "") == 0){
222 		/*
223 		 * make a fake directory for each kid
224 		 * all we care about is the name
225 		 */
226 		if(parent == nil){
227 			nulldir(&d);
228 			d.mode = DMDIR|0600;
229 			d.qid.type = QTDIR;
230 			d.name = nbuf;
231 			nbuf[1] = '\0';
232 			for(i = '1'; i <= '4'; i++){
233 				nbuf[0] = i;
234 				n = convD2M(&d, dbuf, sizeof(dbuf));
235 				if(n <= BIT16SZ)
236 					fprint(2, "bad convD2M %d\n", n);
237 				write(fd, dbuf, n);
238 			}
239 		}
240 	}else if(strcmp(f, "mimeheader") == 0){
241 		if(parent != nil){
242 			switch(m->id){
243 			case 1:
244 			case 2:
245 				fprint(fd, "%s", bogusMimeText);
246 				break;
247 			case 3:
248 			case 4:
249 				fprint(fd, "%s", bogusMimeBinary);
250 				break;
251 			}
252 		}
253 	}else if(strcmp(f, "rawheader") == 0){
254 		if(parent == nil){
255 			date2tm(&tm, m->unixDate);
256 			rfc822date(buf, sizeof(buf), &tm);
257 			fprint(fd,
258 				"Date: %s\r\n"
259 				"From: imap4 daemon <%s@%s>\r\n"
260 				"To: <%s@%s>\r\n"
261 				"Subject: This message was illegal or corrupted\r\n"
262 				"MIME-Version: 1.0\r\n"
263 				"Content-Type: multipart/mixed;\r\n\tboundary=\"upas-%s\"\r\n",
264 					buf, username, site, username, site, m->info[IDigest]);
265 		}
266 	}else if(strcmp(f, "rawbody") == 0){
267 		fd1 = msgFile(p, "raw");
268 		strcpy(p->efs, "rawbody");
269 		fd2 = cdOpen(p->fsDir, p->fs, OREAD);
270 		if(fd1 < 0 || fd2 < 0){
271 			close(fd);
272 			close(fd1);
273 			close(fd2);
274 			return -1;
275 		}
276 		if(parent == nil){
277 			fprint(fd,
278 				"This is a multi-part message in MIME format.\r\n"
279 				"--upas-%s\r\n"
280 				"%s"
281 				"\r\n"
282 				"%s"
283 				"\r\n",
284 					m->info[IDigest], bogusMimeText, bogusBody);
285 
286 			fprint(fd,
287 				"--upas-%s\r\n"
288 				"%s"
289 				"\r\n",
290 					m->info[IDigest], bogusMimeText);
291 			bodystrip(fd1, fd);
292 
293 			fprint(fd,
294 				"--upas-%s\r\n"
295 				"%s"
296 				"\r\n",
297 					m->info[IDigest], bogusMimeBinary);
298 			seek(fd1, 0, 0);
299 			body64(fd1, fd);
300 
301 			fprint(fd,
302 				"--upas-%s\r\n"
303 				"%s"
304 				"\r\n",
305 					m->info[IDigest], bogusMimeBinary);
306 			body64(fd2, fd);
307 
308 			fprint(fd, "--upas-%s--\r\n", m->info[IDigest]);
309 		}else{
310 			switch(m->id){
311 			case 1:
312 				fprint(fd, "%s", bogusBody);
313 				break;
314 			case 2:
315 				bodystrip(fd1, fd);
316 				break;
317 			case 3:
318 				body64(fd1, fd);
319 				break;
320 			case 4:
321 				body64(fd2, fd);
322 				break;
323 			}
324 		}
325 		close(fd1);
326 		close(fd2);
327 	}
328 	seek(fd, 0, 0);
329 	return fd;
330 }
331 
332 int
333 msgIsMulti(Header *h)
334 {
335 	return h->type != nil && cistrcmp("multipart", h->type->s) == 0;
336 }
337 
338 int
339 msgIsRfc822(Header *h)
340 {
341 	return h->type != nil && cistrcmp("message", h->type->s) == 0 && cistrcmp("rfc822", h->type->t) == 0;
342 }
343 
344 /*
345  * check if a message has been deleted by someone else
346  */
347 void
348 msgDead(Msg *m)
349 {
350 	if(m->expunged)
351 		return;
352 	*m->efs = '\0';
353 	if(!cdExists(m->fsDir, m->fs))
354 		m->expunged = 1;
355 }
356 
357 /*
358  * make sure the message has valid associated info
359  * used for ISubject, IDigest, IInReplyTo, IMessageId.
360  */
361 int
362 msgInfo(Msg *m)
363 {
364 	char *s;
365 	int i;
366 
367 	if(m->info[0] != nil)
368 		return 1;
369 
370 	i = msgReadFile(m, "info", &m->iBuf);
371 	if(i < 0)
372 		return 0;
373 
374 	s = m->iBuf;
375 	for(i = 0; i < IMax; i++){
376 		m->info[i] = s;
377 		s = strchr(s, '\n');
378 		if(s == nil)
379 			break;
380 		*s++ = '\0';
381 	}
382 	for(; i < IMax; i++)
383 		m->info[i] = nil;
384 
385 	for(i = 0; i < IMax; i++)
386 		if(infoIsNil(m->info[i]))
387 			m->info[i] = nil;
388 
389 	return 1;
390 }
391 
392 /*
393  * make sure the message has valid mime structure
394  * and sub-messages
395  */
396 int
397 msgStruct(Msg *m, int top)
398 {
399 	Msg *k, head, *last;
400 	Dir *d;
401 	char *s;
402 	ulong max, id;
403 	int i, nd, fd, ns;
404 
405 	if(m->kids != nil)
406 		return 1;
407 
408 	if(m->expunged
409 	|| !msgInfo(m)
410 	|| !msgUnix(m, top)
411 	|| !msgBodySize(m)
412 	|| !msgHeader(m, &m->mime, "mimeheader")
413 	|| (top || msgIsRfc822(&m->mime) || msgIsMulti(&m->mime)) && !msgHeader(m, &m->head, "rawheader")){
414 		if(top && m->bogus && !(m->bogus & BogusTried)){
415 			m->bogus |= BogusTried;
416 			return msgStruct(m, top);
417 		}
418 		msgDead(m);
419 		return 0;
420 	}
421 
422 	/*
423 	 * if a message has no kids, it has a kid which is just the body of the real message
424 	 */
425 	if(!msgIsMulti(&m->head) && !msgIsMulti(&m->mime) && !msgIsRfc822(&m->head) && !msgIsRfc822(&m->mime)){
426 		k = MKZ(Msg);
427 		k->id = 1;
428 		k->fsDir = m->fsDir;
429 		k->bogus = m->bogus;
430 		k->parent = m->parent;
431 		ns = m->efs - m->fs;
432 		k->fs = emalloc(ns + (MsgNameLen + 1));
433 		memmove(k->fs, m->fs, ns);
434 		k->efs = k->fs + ns;
435 		*k->efs = '\0';
436 		k->size = m->size;
437 		m->kids = k;
438 		return 1;
439 	}
440 
441 	/*
442 	 * read in all child messages messages
443 	 */
444 	fd = msgFile(m, "");
445 	if(fd < 0){
446 		msgDead(m);
447 		return 0;
448 	}
449 
450 	max = 0;
451 	head.next = nil;
452 	last = &head;
453 	while((nd = dirread(fd, &d)) > 0){
454 		for(i = 0; i < nd; i++){
455 			s = d[i].name;
456 			id = strtol(s, &s, 10);
457 			if(id <= max || *s != '\0'
458 			|| (d[i].mode & DMDIR) != DMDIR)
459 				continue;
460 
461 			max = id;
462 
463 			k = MKZ(Msg);
464 			k->id = id;
465 			k->fsDir = m->fsDir;
466 			k->bogus = m->bogus;
467 			k->parent = m;
468 			ns = strlen(m->fs);
469 			k->fs = emalloc(ns + 2 * (MsgNameLen + 1));
470 			k->efs = seprint(k->fs, k->fs + ns + (MsgNameLen + 1), "%s%lud/", m->fs, id);
471 			k->prev = last;
472 			k->size = ~0UL;
473 			k->lines = ~0UL;
474 			last->next = k;
475 			last = k;
476 		}
477 	}
478 	close(fd);
479 	m->kids = head.next;
480 
481 	/*
482 	 * if kids fail, just whack them
483 	 */
484 	top = top && (msgIsRfc822(&m->head) || msgIsMulti(&m->head));
485 	for(k = m->kids; k != nil; k = k->next){
486 		if(!msgStruct(k, top)){
487 			for(k = m->kids; k != nil; ){
488 				last = k;
489 				k = k->next;
490 				freeMsg(last);
491 			}
492 			m->kids = nil;
493 			break;
494 		}
495 	}
496 	return 1;
497 }
498 
499 static long
500 msgReadFile(Msg *m, char *file, char **ss)
501 {
502 	Dir *d;
503 	char *s, buf[BufSize];
504 	vlong length;
505 	long n, nn;
506 	int fd;
507 
508 	fd = msgFile(m, file);
509 	if(fd < 0){
510 		msgDead(m);
511 		return -1;
512 	}
513 
514 	n = read(fd, buf, BufSize);
515 	if(n < BufSize){
516 		close(fd);
517 		if(n < 0){
518 			*ss = nil;
519 			return -1;
520 		}
521 		s = emalloc(n + 1);
522 		memmove(s, buf, n);
523 		s[n] = '\0';
524 		*ss = s;
525 		return n;
526 	}
527 
528 	d = dirfstat(fd);
529 	if(d == nil){
530 		close(fd);
531 		return -1;
532 	}
533 	length = d->length;
534 	free(d);
535 	nn = length;
536 	s = emalloc(nn + 1);
537 	memmove(s, buf, n);
538 	if(nn > n)
539 		nn = readn(fd, s+n, nn-n) + n;
540 	close(fd);
541 	if(nn != length){
542 		free(s);
543 		return -1;
544 	}
545 	s[nn] = '\0';
546 	*ss = s;
547 	return nn;
548 }
549 
550 static void
551 freeMAddr(MAddr *a)
552 {
553 	MAddr *p;
554 
555 	while(a != nil){
556 		p = a;
557 		a = a->next;
558 		free(p->personal);
559 		free(p->box);
560 		free(p->host);
561 		free(p);
562 	}
563 }
564 
565 /*
566  * the message is corrupted or illegal.
567  * reset message fields.  msgStruct will reparse the message,
568  * relying on msgFile to make up corrected body parts.
569  */
570 static int
571 msgBogus(Msg *m, int flags)
572 {
573 	if(!(m->bogus & flags))
574 		m->bogus |= flags;
575 	m->lines = ~0;
576 	free(m->head.buf);
577 	free(m->mime.buf);
578 	memset(&m->head, 0, sizeof(Header));
579 	memset(&m->mime, 0, sizeof(Header));
580 	return 0;
581 }
582 
583 /*
584  *  stolen from upas/marshal; base64 encodes from one fd to another.
585  *
586  *  the size of buf is very important to enc64.  Anything other than
587  *  a multiple of 3 will cause enc64 to output a termination sequence.
588  *  To ensure that a full buf corresponds to a multiple of complete lines,
589  *  we make buf a multiple of 3*18 since that's how many enc64 sticks on
590  *  a single line.  This avoids short lines in the output which is pleasing
591  *  but not necessary.
592  */
593 static int
594 enc64x18(char *out, int lim, uchar *in, int n)
595 {
596 	int m, mm, nn;
597 
598 	nn = 0;
599 	for(; n > 0; n -= m){
600 		m = 18 * 3;
601 		if(m > n)
602 			m = n;
603 		mm = enc64(out, lim - nn, in, m);
604 		in += m;
605 		out += mm;
606 		*out++ = '\r';
607 		*out++ = '\n';
608 		nn += mm + 2;
609 	}
610 	return nn;
611 }
612 
613 static void
614 body64(int in, int out)
615 {
616 	uchar buf[3*18*54];
617 	char obuf[3*18*54*2];
618 	int m, n;
619 
620 	for(;;){
621 		n = read(in, buf, sizeof(buf));
622 		if(n < 0)
623 			return;
624 		if(n == 0)
625 			break;
626 		m = enc64x18(obuf, sizeof(obuf), buf, n);
627 		if(write(out, obuf, m) < 0)
628 			return;
629 	}
630 }
631 
632 /*
633  * strip all non-printable characters from a file
634  */
635 static void
636 bodystrip(int in, int out)
637 {
638 	uchar buf[3*18*54];
639 	int m, n, i, c;
640 
641 	for(;;){
642 		n = read(in, buf, sizeof(buf));
643 		if(n < 0)
644 			return;
645 		if(n == 0)
646 			break;
647 		m = 0;
648 		for(i = 0; i < n; i++){
649 			c = buf[i];
650 			if(c > 0x1f && c < 0x7f		/* normal characters */
651 			|| c >= 0x9 && c <= 0xd)	/* \t, \n, vertical tab, form feed, \r */
652 				buf[m++] = c;
653 		}
654 
655 		if(m && write(out, buf, m) < 0)
656 			return;
657 	}
658 }
659 
660 /*
661  * read in the message body to count \n without a preceding \r
662  */
663 static int
664 msgBodySize(Msg *m)
665 {
666 	Dir *d;
667 	char buf[BufSize + 2], *s, *se;
668 	vlong length;
669 	ulong size, lines, bad;
670 	int n, fd, c;
671 
672 	if(m->lines != ~0UL)
673 		return 1;
674 	fd = msgFile(m, "rawbody");
675 	if(fd < 0)
676 		return 0;
677 	d = dirfstat(fd);
678 	if(d == nil){
679 		close(fd);
680 		return 0;
681 	}
682 	length = d->length;
683 	free(d);
684 
685 	size = 0;
686 	lines = 0;
687 	bad = 0;
688 	buf[0] = ' ';
689 	for(;;){
690 		n = read(fd, &buf[1], BufSize);
691 		if(n <= 0)
692 			break;
693 		size += n;
694 		se = &buf[n + 1];
695 		for(s = &buf[1]; s < se; s++){
696 			c = *s;
697 			if(c == '\0'){
698 				close(fd);
699 				return msgBogus(m, BogusBody);
700 			}
701 			if(c != '\n')
702 				continue;
703 			if(s[-1] != '\r')
704 				bad++;
705 			lines++;
706 		}
707 		buf[0] = buf[n];
708 	}
709 	if(size != length)
710 		bye("bad length reading rawbody");
711 	size += bad;
712 	m->size = size;
713 	m->lines = lines;
714 	close(fd);
715 	return 1;
716 }
717 
718 /*
719  * retrieve information from the unixheader file
720  */
721 static int
722 msgUnix(Msg *m, int top)
723 {
724 	Tm tm;
725 	char *s, *ss;
726 
727 	if(m->unixDate != nil)
728 		return 1;
729 
730 	if(!top){
731 bogus:
732 		m->unixDate = estrdup("");
733 		m->unixFrom = unixFrom(nil);
734 		return 1;
735 	}
736 
737 	if(msgReadFile(m, "unixheader", &ss) < 0)
738 		return 0;
739 	s = ss;
740 	s = strchr(s, ' ');
741 	if(s == nil){
742 		free(ss);
743 		goto bogus;
744 	}
745 	s++;
746 	m->unixFrom = unixFrom(s);
747 	s = (char*)headStr;
748 	if(date2tm(&tm, s) == nil)
749 		s = m->info[IUnixDate];
750 	if(s == nil){
751 		free(ss);
752 		goto bogus;
753 	}
754 	m->unixDate = estrdup(s);
755 	free(ss);
756 	return 1;
757 }
758 
759 /*
760  * parse the address in the unix header
761  * last line of defence, so must return something
762  */
763 static MAddr *
764 unixFrom(char *s)
765 {
766 	MAddr *a;
767 	char *e, *t;
768 
769 	if(s == nil)
770 		return nil;
771 	headStr = (uchar*)s;
772 	t = emalloc(strlen(s) + 2);
773 	e = headAddrSpec(t, nil);
774 	if(e == nil)
775 		a = nil;
776 	else{
777 		if(*e != '\0')
778 			*e++ = '\0';
779 		else
780 			e = site;
781 		a = MKZ(MAddr);
782 
783 		a->box = estrdup(t);
784 		a->host = estrdup(e);
785 	}
786 	free(t);
787 	return a;
788 }
789 
790 /*
791  * read in the entire header,
792  * and parse out any existing mime headers
793  */
794 static int
795 msgHeader(Msg *m, Header *h, char *file)
796 {
797 	char *s, *ss, *t, *te;
798 	ulong lines, n, nn;
799 	long ns;
800 	int dated, c;
801 
802 	if(h->buf != nil)
803 		return 1;
804 
805 	ns = msgReadFile(m, file, &ss);
806 	if(ns < 0)
807 		return 0;
808 	s = ss;
809 	n = ns;
810 
811 	/*
812 	 * count lines ending with \n and \r\n
813 	 * add an extra line at the end, since upas/fs headers
814 	 * don't have a terminating \r\n
815 	 */
816 	lines = 1;
817 	te = s + ns;
818 	for(t = s; t < te; t++){
819 		c = *t;
820 		if(c == '\0')
821 			return msgBogus(m, BogusHeader);
822 		if(c != '\n')
823 			continue;
824 		if(t == s || t[-1] != '\r')
825 			n++;
826 		lines++;
827 	}
828 	if(t > s && t[-1] != '\n'){
829 		if(t[-1] != '\r')
830 			n++;
831 		n++;
832 	}
833 	n += 2;
834 	h->buf = emalloc(n + 1);
835 	h->size = n;
836 	h->lines = lines;
837 
838 	/*
839 	 * make sure all headers end in \r\n
840 	 */
841 	nn = 0;
842 	for(t = s; t < te; t++){
843 		c = *t;
844 		if(c == '\n'){
845 			if(!nn || h->buf[nn - 1] != '\r')
846 				h->buf[nn++] = '\r';
847 			lines++;
848 		}
849 		h->buf[nn++] = c;
850 	}
851 	if(nn && h->buf[nn-1] != '\n'){
852 		if(h->buf[nn-1] != '\r')
853 			h->buf[nn++] = '\r';
854 		h->buf[nn++] = '\n';
855 	}
856 	h->buf[nn++] = '\r';
857 	h->buf[nn++] = '\n';
858 	h->buf[nn] = '\0';
859 	if(nn != n)
860 		bye("misconverted header %d %d", nn, n);
861 	free(s);
862 
863 	/*
864 	 * and parse some mime headers
865 	 */
866 	headStr = (uchar*)h->buf;
867 	dated = 0;
868 	while(s = headAtom(headFieldStop)){
869 		if(cistrcmp(s, "content-type") == 0)
870 			mimeType(h);
871 		else if(cistrcmp(s, "content-transfer-encoding") == 0)
872 			mimeEncoding(h);
873 		else if(cistrcmp(s, "content-id") == 0)
874 			mimeId(h);
875 		else if(cistrcmp(s, "content-description") == 0)
876 			mimeDescription(h);
877 		else if(cistrcmp(s, "content-disposition") == 0)
878 			mimeDisposition(h);
879 		else if(cistrcmp(s, "content-md5") == 0)
880 			mimeMd5(h);
881 		else if(cistrcmp(s, "content-language") == 0)
882 			mimeLanguage(h);
883 		else if(h == &m->head && cistrcmp(s, "from") == 0)
884 			m->from = headMAddr(m->from);
885 		else if(h == &m->head && cistrcmp(s, "to") == 0)
886 			m->to = headMAddr(m->to);
887 		else if(h == &m->head && cistrcmp(s, "reply-to") == 0)
888 			m->replyTo = headMAddr(m->replyTo);
889 		else if(h == &m->head && cistrcmp(s, "sender") == 0)
890 			m->sender = headMAddr(m->sender);
891 		else if(h == &m->head && cistrcmp(s, "cc") == 0)
892 			m->cc = headMAddr(m->cc);
893 		else if(h == &m->head && cistrcmp(s, "bcc") == 0)
894 			m->bcc = headMAddr(m->bcc);
895 		else if(h == &m->head && cistrcmp(s, "date") == 0)
896 			dated = 1;
897 		headSkip();
898 		free(s);
899 	}
900 
901 	if(h == &m->head){
902 		if(m->from == nil){
903 			m->from = m->unixFrom;
904 			if(m->from != nil){
905 				s = maddrStr(m->from);
906 				msgAddHead(m, "From", s);
907 				free(s);
908 			}
909 		}
910 		if(m->sender == nil)
911 			m->sender = m->from;
912 		if(m->replyTo == nil)
913 			m->replyTo = m->from;
914 
915 		if(infoIsNil(m->info[IDate]))
916 			m->info[IDate] = m->unixDate;
917 		if(!dated && m->from != nil)
918 			msgAddDate(m);
919 	}
920 	return 1;
921 }
922 
923 /*
924  * prepend head: body to the cached header
925  */
926 static void
927 msgAddHead(Msg *m, char *head, char *body)
928 {
929 	char *s;
930 	long size, n;
931 
932 	n = strlen(head) + strlen(body) + 4;
933 	size = m->head.size + n;
934 	s = emalloc(size + 1);
935 	snprint(s, size + 1, "%s: %s\r\n%s", head, body, m->head.buf);
936 	free(m->head.buf);
937 	m->head.buf = s;
938 	m->head.size = size;
939 	m->head.lines++;
940 }
941 
942 static void
943 msgAddDate(Msg *m)
944 {
945 	Tm tm;
946 	char buf[64];
947 
948 	/* don't bother if we don't have a date */
949 	if(infoIsNil(m->info[IDate]))
950 		return;
951 
952 	date2tm(&tm, m->info[IDate]);
953 	rfc822date(buf, sizeof(buf), &tm);
954 	msgAddHead(m, "Date", buf);
955 }
956 
957 static MimeHdr*
958 mkMimeHdr(char *s, char *t, MimeHdr *next)
959 {
960 	MimeHdr *mh;
961 
962 	mh = MK(MimeHdr);
963 	mh->s = s;
964 	mh->t = t;
965 	mh->next = next;
966 	return mh;
967 }
968 
969 static void
970 freeMimeHdr(MimeHdr *mh)
971 {
972 	MimeHdr *last;
973 
974 	while(mh != nil){
975 		last = mh;
976 		mh = mh->next;
977 		free(last->s);
978 		free(last->t);
979 		free(last);
980 	}
981 }
982 
983 static void
984 cleanupHeader(Header *h)
985 {
986 	freeMimeHdr(h->type);
987 	freeMimeHdr(h->id);
988 	freeMimeHdr(h->description);
989 	freeMimeHdr(h->encoding);
990 	freeMimeHdr(h->md5);
991 	freeMimeHdr(h->disposition);
992 	freeMimeHdr(h->language);
993 }
994 
995 /*
996  * parser for rfc822 & mime header fields
997  */
998 
999 /*
1000  * type		: 'content-type' ':' token '/' token params
1001  */
1002 static void
1003 mimeType(Header *h)
1004 {
1005 	char *s, *t;
1006 
1007 	if(headChar(1) != ':')
1008 		return;
1009 	s = headAtom(mimeTokenStop);
1010 	if(s == nil || headChar(1) != '/'){
1011 		free(s);
1012 		return;
1013 	}
1014 	t = headAtom(mimeTokenStop);
1015 	if(t == nil){
1016 		free(s);
1017 		return;
1018 	}
1019 	h->type = mkMimeHdr(s, t, mimeParams());
1020 }
1021 
1022 /*
1023  * params	:
1024  *		| params ';' token '=' token
1025  * 		| params ';' token '=' quoted-str
1026  */
1027 static MimeHdr*
1028 mimeParams(void)
1029 {
1030 	MimeHdr head, *last;
1031 	char *s, *t;
1032 
1033 	head.next = nil;
1034 	last = &head;
1035 	for(;;){
1036 		if(headChar(1) != ';')
1037 			break;
1038 		s = headAtom(mimeTokenStop);
1039 		if(s == nil || headChar(1) != '='){
1040 			free(s);
1041 			break;
1042 		}
1043 		if(headChar(0) == '"'){
1044 			t = headQuoted('"', '"');
1045 			stripQuotes(t);
1046 		}else
1047 			t = headAtom(mimeTokenStop);
1048 		if(t == nil){
1049 			free(s);
1050 			break;
1051 		}
1052 		last->next = mkMimeHdr(s, t, nil);
1053 		last = last->next;
1054 	}
1055 	return head.next;
1056 }
1057 
1058 /*
1059  * encoding	: 'content-transfer-encoding' ':' token
1060  */
1061 static void
1062 mimeEncoding(Header *h)
1063 {
1064 	char *s;
1065 
1066 	if(headChar(1) != ':')
1067 		return;
1068 	s = headAtom(mimeTokenStop);
1069 	if(s == nil)
1070 		return;
1071 	h->encoding = mkMimeHdr(s, nil, nil);
1072 }
1073 
1074 /*
1075  * mailaddr	: ':' addresses
1076  */
1077 static MAddr*
1078 headMAddr(MAddr *old)
1079 {
1080 	MAddr *a;
1081 
1082 	if(headChar(1) != ':')
1083 		return old;
1084 
1085 	if(headChar(0) == '\n')
1086 		return old;
1087 
1088 	a = headAddresses();
1089 	if(a == nil)
1090 		return old;
1091 
1092 	freeMAddr(old);
1093 	return a;
1094 }
1095 
1096 /*
1097  * addresses	: address | addresses ',' address
1098  */
1099 static MAddr*
1100 headAddresses(void)
1101 {
1102 	MAddr *addr, *tail, *a;
1103 
1104 	addr = headAddress();
1105 	if(addr == nil)
1106 		return nil;
1107 	tail = addr;
1108 	while(headChar(0) == ','){
1109 		headChar(1);
1110 		a = headAddress();
1111 		if(a == nil){
1112 			freeMAddr(addr);
1113 			return nil;
1114 		}
1115 		tail->next = a;
1116 		tail = a;
1117 	}
1118 	return addr;
1119 }
1120 
1121 /*
1122  * address	: mailbox | group
1123  * group	: phrase ':' mboxes ';' | phrase ':' ';'
1124  * mailbox	: addr-spec
1125  *		| optphrase '<' addr-spec '>'
1126  *		| optphrase '<' route ':' addr-spec '>'
1127  * optphrase	: | phrase
1128  * route	: '@' domain
1129  *		| route ',' '@' domain
1130  * personal names are the phrase before '<',
1131  * or a comment before or after a simple addr-spec
1132  */
1133 static MAddr*
1134 headAddress(void)
1135 {
1136 	MAddr *addr;
1137 	uchar *hs;
1138 	char *s, *e, *w, *personal;
1139 	int c;
1140 
1141 	s = emalloc(strlen((char*)headStr) + 2);
1142 	e = s;
1143 	personal = headSkipWhite(1);
1144 	c = headChar(0);
1145 	if(c == '<')
1146 		w = nil;
1147 	else{
1148 		w = headWord();
1149 		c = headChar(0);
1150 	}
1151 	if(c == '.' || c == '@' || c == ',' || c == '\n' || c == '\0'){
1152 		lastWhite = headStr;
1153 		e = headAddrSpec(s, w);
1154 		if(personal == nil){
1155 			hs = headStr;
1156 			headStr = lastWhite;
1157 			personal = headSkipWhite(1);
1158 			headStr = hs;
1159 		}
1160 	}else{
1161 		if(c != '<' || w != nil){
1162 			free(personal);
1163 			if(!headPhrase(e, w)){
1164 				free(s);
1165 				return nil;
1166 			}
1167 
1168 			/*
1169 			 * ignore addresses with groups,
1170 			 * so the only thing left if <
1171 			 */
1172 			c = headChar(1);
1173 			if(c != '<'){
1174 				free(s);
1175 				return nil;
1176 			}
1177 			personal = estrdup(s);
1178 		}else
1179 			headChar(1);
1180 
1181 		/*
1182 		 * after this point, we need to free personal before returning.
1183 		 * set e to nil to everything afterwards fails.
1184 		 *
1185 		 * ignore routes, they are useless, and heavily discouraged in rfc1123.
1186 		 * imap4 reports them up to, but not including, the terminating :
1187 		 */
1188 		e = s;
1189 		c = headChar(0);
1190 		if(c == '@'){
1191 			for(;;){
1192 				c = headChar(1);
1193 				if(c != '@'){
1194 					e = nil;
1195 					break;
1196 				}
1197 				headDomain(e);
1198 				c = headChar(1);
1199 				if(c != ','){
1200 					e = s;
1201 					break;
1202 				}
1203 			}
1204 			if(c != ':')
1205 				e = nil;
1206 		}
1207 
1208 		if(e != nil)
1209 			e = headAddrSpec(s, nil);
1210 		if(headChar(1) != '>')
1211 			e = nil;
1212 	}
1213 
1214 	/*
1215 	 * e points to @host, or nil if an error occured
1216 	 */
1217 	if(e == nil){
1218 		free(personal);
1219 		addr = nil;
1220 	}else{
1221 		if(*e != '\0')
1222 			*e++ = '\0';
1223 		else
1224 			e = site;
1225 		addr = MKZ(MAddr);
1226 
1227 		addr->personal = personal;
1228 		addr->box = estrdup(s);
1229 		addr->host = estrdup(e);
1230 	}
1231 	free(s);
1232 	return addr;
1233 }
1234 
1235 /*
1236  * phrase	: word
1237  *		| phrase word
1238  * w is the optional initial word of the phrase
1239  * returns the end of the phrase, or nil if a failure occured
1240  */
1241 static char*
1242 headPhrase(char *e, char *w)
1243 {
1244 	int c;
1245 
1246 	for(;;){
1247 		if(w == nil){
1248 			w = headWord();
1249 			if(w == nil)
1250 				return nil;
1251 		}
1252 		if(w[0] == '"')
1253 			stripQuotes(w);
1254 		strcpy(e, w);
1255 		free(w);
1256 		w = nil;
1257 		e = strchr(e, '\0');
1258 		c = headChar(0);
1259 		if(c <= ' ' || strchr(headAtomStop, c) != nil && c != '"')
1260 			break;
1261 		*e++ = ' ';
1262 		*e = '\0';
1263 	}
1264 	return e;
1265 }
1266 
1267 /*
1268  * addr-spec	: local-part '@' domain
1269  *		| local-part			extension to allow ! and local names
1270  * local-part	: word
1271  *		| local-part '.' word
1272  *
1273  * if no '@' is present, rewrite d!e!f!u as @d,@e:u@f,
1274  * where d, e, f are valid domain components.
1275  * the @d,@e: is ignored, since routes are ignored.
1276  * perhaps they should be rewritten as e!f!u@d, but that is inconsistent with upas.
1277  *
1278  * returns a pointer to '@', the end if none, or nil if there was an error
1279  */
1280 static char*
1281 headAddrSpec(char *e, char *w)
1282 {
1283 	char *s, *at, *b, *bang, *dom;
1284 	int c;
1285 
1286 	s = e;
1287 	for(;;){
1288 		if(w == nil){
1289 			w = headWord();
1290 			if(w == nil)
1291 				return nil;
1292 		}
1293 		strcpy(e, w);
1294 		free(w);
1295 		w = nil;
1296 		e = strchr(e, '\0');
1297 		lastWhite = headStr;
1298 		c = headChar(0);
1299 		if(c != '.')
1300 			break;
1301 		headChar(1);
1302 		*e++ = '.';
1303 		*e = '\0';
1304 	}
1305 
1306 	if(c != '@'){
1307 		/*
1308 		 * extenstion: allow name without domain
1309 		 * check for domain!xxx
1310 		 */
1311 		bang = domBang(s);
1312 		if(bang == nil)
1313 			return e;
1314 
1315 		/*
1316 		 * if dom1!dom2!xxx, ignore dom1!
1317 		 */
1318 		dom = s;
1319 		for(; b = domBang(bang + 1); bang = b)
1320 			dom = bang + 1;
1321 
1322 		/*
1323 		 * convert dom!mbox into mbox@dom
1324 		 */
1325 		*bang = '@';
1326 		strrev(dom, bang);
1327 		strrev(bang+1, e);
1328 		strrev(dom, e);
1329 		bang = &dom[e - bang - 1];
1330 		if(dom > s){
1331 			bang -= dom - s;
1332 			for(e = s; *e = *dom; e++)
1333 				dom++;
1334 		}
1335 
1336 		/*
1337 		 * eliminate a trailing '.'
1338 		 */
1339 		if(e[-1] == '.')
1340 			e[-1] = '\0';
1341 		return bang;
1342 	}
1343 	headChar(1);
1344 
1345 	at = e;
1346 	*e++ = '@';
1347 	*e = '\0';
1348 	if(!headDomain(e))
1349 		return nil;
1350 	return at;
1351 }
1352 
1353 /*
1354  * find the ! in domain!rest, where domain must have at least
1355  * one internal '.'
1356  */
1357 static char*
1358 domBang(char *s)
1359 {
1360 	int dot, c;
1361 
1362 	dot = 0;
1363 	for(; c = *s; s++){
1364 		if(c == '!'){
1365 			if(!dot || dot == 1 && s[-1] == '.' || s[1] == '\0')
1366 				return nil;
1367 			return s;
1368 		}
1369 		if(c == '"')
1370 			break;
1371 		if(c == '.')
1372 			dot++;
1373 	}
1374 	return nil;
1375 }
1376 
1377 /*
1378  * domain	: sub-domain
1379  *		| domain '.' sub-domain
1380  * returns the end of the domain, or nil if a failure occured
1381  */
1382 static char*
1383 headDomain(char *e)
1384 {
1385 	char *w;
1386 
1387 	for(;;){
1388 		w = headSubDomain();
1389 		if(w == nil)
1390 			return nil;
1391 		strcpy(e, w);
1392 		free(w);
1393 		e = strchr(e, '\0');
1394 		lastWhite = headStr;
1395 		if(headChar(0) != '.')
1396 			break;
1397 		headChar(1);
1398 		*e++ = '.';
1399 		*e = '\0';
1400 	}
1401 	return e;
1402 }
1403 
1404 /*
1405  * id		: 'content-id' ':' msg-id
1406  * msg-id	: '<' addr-spec '>'
1407  */
1408 static void
1409 mimeId(Header *h)
1410 {
1411 	char *s, *e, *w;
1412 
1413 	if(headChar(1) != ':')
1414 		return;
1415 	if(headChar(1) != '<')
1416 		return;
1417 
1418 	s = emalloc(strlen((char*)headStr) + 3);
1419 	e = s;
1420 	*e++ = '<';
1421 	e = headAddrSpec(e, nil);
1422 	if(e == nil || headChar(1) != '>'){
1423 		free(s);
1424 		return;
1425 	}
1426 	e = strchr(e, '\0');
1427 	*e++ = '>';
1428 	e[0] = '\0';
1429 	w = strdup(s);
1430 	free(s);
1431 	h->id = mkMimeHdr(w, nil, nil);
1432 }
1433 
1434 /*
1435  * description	: 'content-description' ':' *text
1436  */
1437 static void
1438 mimeDescription(Header *h)
1439 {
1440 	if(headChar(1) != ':')
1441 		return;
1442 	headSkipWhite(0);
1443 	h->description = mkMimeHdr(headText(), nil, nil);
1444 }
1445 
1446 /*
1447  * disposition	: 'content-disposition' ':' token params
1448  */
1449 static void
1450 mimeDisposition(Header *h)
1451 {
1452 	char *s;
1453 
1454 	if(headChar(1) != ':')
1455 		return;
1456 	s = headAtom(mimeTokenStop);
1457 	if(s == nil)
1458 		return;
1459 	h->disposition = mkMimeHdr(s, nil, mimeParams());
1460 }
1461 
1462 /*
1463  * md5		: 'content-md5' ':' token
1464  */
1465 static void
1466 mimeMd5(Header *h)
1467 {
1468 	char *s;
1469 
1470 	if(headChar(1) != ':')
1471 		return;
1472 	s = headAtom(mimeTokenStop);
1473 	if(s == nil)
1474 		return;
1475 	h->md5 = mkMimeHdr(s, nil, nil);
1476 }
1477 
1478 /*
1479  * language	: 'content-language' ':' langs
1480  * langs	: token
1481  *		| langs commas token
1482  * commas	: ','
1483  *		| commas ','
1484  */
1485 static void
1486 mimeLanguage(Header *h)
1487 {
1488 	MimeHdr head, *last;
1489 	char *s;
1490 
1491 	head.next = nil;
1492 	last = &head;
1493 	for(;;){
1494 		s = headAtom(mimeTokenStop);
1495 		if(s == nil)
1496 			break;
1497 		last->next = mkMimeHdr(s, nil, nil);
1498 		last = last->next;
1499 		while(headChar(0) != ',')
1500 			headChar(1);
1501 	}
1502 	h->language = head.next;
1503 }
1504 
1505 /*
1506  * token	: 1*<char 33-255, except "()<>@,;:\\\"/[]?=" aka mimeTokenStop>
1507  * atom		: 1*<chars 33-255, except "()<>@,;:\\\".[]" aka headAtomStop>
1508  * note this allows 8 bit characters, which occur in utf.
1509  */
1510 static char*
1511 headAtom(char *disallowed)
1512 {
1513 	char *s;
1514 	int c, ns, as;
1515 
1516 	headSkipWhite(0);
1517 
1518 	s = emalloc(StrAlloc);
1519 	as = StrAlloc;
1520 	ns = 0;
1521 	for(;;){
1522 		c = *headStr++;
1523 		if(c <= ' ' || strchr(disallowed, c) != nil){
1524 			headStr--;
1525 			break;
1526 		}
1527 		s[ns++] = c;
1528 		if(ns >= as){
1529 			as += StrAlloc;
1530 			s = erealloc(s, as);
1531 		}
1532 	}
1533 	if(ns == 0){
1534 		free(s);
1535 		return 0;
1536 	}
1537 	s[ns] = '\0';
1538 	return s;
1539 }
1540 
1541 /*
1542  * sub-domain	: atom | domain-lit
1543  */
1544 static char *
1545 headSubDomain(void)
1546 {
1547 	if(headChar(0) == '[')
1548 		return headQuoted('[', ']');
1549 	return headAtom(headAtomStop);
1550 }
1551 
1552 /*
1553  * word	: atom | quoted-str
1554  */
1555 static char *
1556 headWord(void)
1557 {
1558 	if(headChar(0) == '"')
1559 		return headQuoted('"', '"');
1560 	return headAtom(headAtomStop);
1561 }
1562 
1563 /*
1564  * q is a quoted string.  remove enclosing " and and \ escapes
1565  */
1566 static void
1567 stripQuotes(char *q)
1568 {
1569 	char *s;
1570 	int c;
1571 
1572 	if(q == nil)
1573 		return;
1574 	s = q++;
1575 	while(c = *q++){
1576 		if(c == '\\'){
1577 			c = *q++;
1578 			if(!c)
1579 				return;
1580 		}
1581 		*s++ = c;
1582 	}
1583 	s[-1] = '\0';
1584 }
1585 
1586 /*
1587  * quoted-str	: '"' *(any char but '"\\\r', or '\' any char, or linear-white-space) '"'
1588  * domain-lit	: '[' *(any char but '[]\\\r', or '\' any char, or linear-white-space) ']'
1589  */
1590 static char *
1591 headQuoted(int start, int stop)
1592 {
1593 	char *s;
1594 	int c, ns, as;
1595 
1596 	if(headChar(1) != start)
1597 		return nil;
1598 	s = emalloc(StrAlloc);
1599 	as = StrAlloc;
1600 	ns = 0;
1601 	s[ns++] = start;
1602 	for(;;){
1603 		c = *headStr;
1604 		if(c == stop){
1605 			headStr++;
1606 			break;
1607 		}
1608 		if(c == '\0'){
1609 			free(s);
1610 			return nil;
1611 		}
1612 		if(c == '\r'){
1613 			headStr++;
1614 			continue;
1615 		}
1616 		if(c == '\n'){
1617 			headStr++;
1618 			while(*headStr == ' ' || *headStr == '\t' || *headStr == '\r' || *headStr == '\n')
1619 				headStr++;
1620 			c = ' ';
1621 		}else if(c == '\\'){
1622 			headStr++;
1623 			s[ns++] = c;
1624 			c = *headStr;
1625 			if(c == '\0'){
1626 				free(s);
1627 				return nil;
1628 			}
1629 			headStr++;
1630 		}else
1631 			headStr++;
1632 		s[ns++] = c;
1633 		if(ns + 1 >= as){	/* leave room for \c or "0 */
1634 			as += StrAlloc;
1635 			s = erealloc(s, as);
1636 		}
1637 	}
1638 	s[ns++] = stop;
1639 	s[ns] = '\0';
1640 	return s;
1641 }
1642 
1643 /*
1644  * headText	: contents of rest of header line
1645  */
1646 static char *
1647 headText(void)
1648 {
1649 	uchar *v;
1650 	char *s;
1651 
1652 	v = headStr;
1653 	headToEnd();
1654 	s = emalloc(headStr - v + 1);
1655 	memmove(s, v, headStr - v);
1656 	s[headStr - v] = '\0';
1657 	return s;
1658 }
1659 
1660 /*
1661  * white space is ' ' '\t' or nested comments.
1662  * skip white space.
1663  * if com and a comment is seen,
1664  * return it's contents and stop processing white space.
1665  */
1666 static char*
1667 headSkipWhite(int com)
1668 {
1669 	char *s;
1670 	int c, incom, as, ns;
1671 
1672 	s = nil;
1673 	as = StrAlloc;
1674 	ns = 0;
1675 	if(com)
1676 		s = emalloc(StrAlloc);
1677 	incom = 0;
1678 	for(; c = *headStr; headStr++){
1679 		switch(c){
1680 		case ' ':
1681 		case '\t':
1682 		case '\r':
1683 			c = ' ';
1684 			break;
1685 		case '\n':
1686 			c = headStr[1];
1687 			if(c != ' ' && c != '\t')
1688 				goto breakout;
1689 			c = ' ';
1690 			break;
1691 		case '\\':
1692 			if(com && incom)
1693 				s[ns++] = c;
1694 			c = headStr[1];
1695 			if(c == '\0')
1696 				goto breakout;
1697 			headStr++;
1698 			break;
1699 		case '(':
1700 			incom++;
1701 			if(incom == 1)
1702 				continue;
1703 			break;
1704 		case ')':
1705 			incom--;
1706 			if(com && !incom){
1707 				s[ns] = '\0';
1708 				return s;
1709 			}
1710 			break;
1711 		default:
1712 			if(!incom)
1713 				goto breakout;
1714 			break;
1715 		}
1716 		if(com && incom && (c != ' ' || ns > 0 && s[ns-1] != ' ')){
1717 			s[ns++] = c;
1718 			if(ns + 1 >= as){	/* leave room for \c or 0 */
1719 				as += StrAlloc;
1720 				s = erealloc(s, as);
1721 			}
1722 		}
1723 	}
1724 breakout:;
1725 	free(s);
1726 	return nil;
1727 }
1728 
1729 /*
1730  * return the next non-white character
1731  */
1732 static int
1733 headChar(int eat)
1734 {
1735 	int c;
1736 
1737 	headSkipWhite(0);
1738 	c = *headStr;
1739 	if(eat && c != '\0' && c != '\n')
1740 		headStr++;
1741 	return c;
1742 }
1743 
1744 static void
1745 headToEnd(void)
1746 {
1747 	uchar *s;
1748 	int c;
1749 
1750 	for(;;){
1751 		s = headStr;
1752 		c = *s++;
1753 		while(c == '\r')
1754 			c = *s++;
1755 		if(c == '\n'){
1756 			c = *s++;
1757 			if(c != ' ' && c != '\t')
1758 				return;
1759 		}
1760 		if(c == '\0')
1761 			return;
1762 		headStr = s;
1763 	}
1764 }
1765 
1766 static void
1767 headSkip(void)
1768 {
1769 	int c;
1770 
1771 	while(c = *headStr){
1772 		headStr++;
1773 		if(c == '\n'){
1774 			c = *headStr;
1775 			if(c == ' ' || c == '\t')
1776 				continue;
1777 			return;
1778 		}
1779 	}
1780 }
1781