1 /****************************************************************************
2  * Copyright (c) 1998,1999,2000 Free Software Foundation, Inc.              *
3  *                                                                          *
4  * Permission is hereby granted, free of charge, to any person obtaining a  *
5  * copy of this software and associated documentation files (the            *
6  * "Software"), to deal in the Software without restriction, including      *
7  * without limitation the rights to use, copy, modify, merge, publish,      *
8  * distribute, distribute with modifications, sublicense, and/or sell       *
9  * copies of the Software, and to permit persons to whom the Software is    *
10  * furnished to do so, subject to the following conditions:                 *
11  *                                                                          *
12  * The above copyright notice and this permission notice shall be included  *
13  * in all copies or substantial portions of the Software.                   *
14  *                                                                          *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
16  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
18  * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
19  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
20  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
21  * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
22  *                                                                          *
23  * Except as contained in this notice, the name(s) of the above copyright   *
24  * holders shall not be used in advertising or otherwise to promote the     *
25  * sale, use or other dealings in this Software without prior written       *
26  * authorization.                                                           *
27  ****************************************************************************/
28 
29 /****************************************************************************
30  *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
31  *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
32  ****************************************************************************/
33 
34 /*
35  *	comp_scan.c --- Lexical scanner for terminfo compiler.
36  *
37  *	_nc_reset_input()
38  *	_nc_get_token()
39  *	_nc_panic_mode()
40  *	int _nc_syntax;
41  *	int _nc_curr_line;
42  *	long _nc_curr_file_pos;
43  *	long _nc_comment_start;
44  *	long _nc_comment_end;
45  */
46 
47 #include <curses.priv.h>
48 
49 #include <ctype.h>
50 #include <term_entry.h>
51 #include <tic.h>
52 
53 MODULE_ID("$Id: comp_scan.c,v 1.47 2000/09/24 01:15:17 tom Exp $")
54 
55 /*
56  * Maximum length of string capability we'll accept before raising an error.
57  * Yes, there is a real capability in /etc/termcap this long, an "is".
58  */
59 #define MAXCAPLEN	600
60 
61 #define iswhite(ch)	(ch == ' '  ||  ch == '\t')
62 
63 int _nc_syntax = 0;		/* termcap or terminfo? */
64 long _nc_curr_file_pos = 0;	/* file offset of current line */
65 long _nc_comment_start = 0;	/* start of comment range before name */
66 long _nc_comment_end = 0;	/* end of comment range before name */
67 long _nc_start_line = 0;	/* start line of current entry */
68 
69 struct token _nc_curr_token =
70 {0, 0, 0};
71 
72 /*****************************************************************************
73  *
74  * Token-grabbing machinery
75  *
76  *****************************************************************************/
77 
78 static bool first_column;	/* See 'next_char()' below */
79 static char separator;		/* capability separator */
80 static int pushtype;		/* type of pushback token */
81 static char pushname[MAX_NAME_SIZE + 1];
82 
83 #if NCURSES_EXT_FUNCS
84 bool _nc_disable_period = FALSE;	/* used by tic -a option */
85 #endif
86 
87 static int last_char(void);
88 static int next_char(void);
89 static long stream_pos(void);
90 static bool end_of_stream(void);
91 static void push_back(char c);
92 
93 /* Assume we may be looking at a termcap-style continuation */
94 static inline int
95 eat_escaped_newline(int ch)
96 {
97     if (ch == '\\')
98 	while ((ch = next_char()) == '\n' || iswhite(ch))
99 	    continue;
100     return ch;
101 }
102 
103 /*
104  *	int
105  *	get_token()
106  *
107  *	Scans the input for the next token, storing the specifics in the
108  *	global structure 'curr_token' and returning one of the following:
109  *
110  *		NAMES		A line beginning in column 1.  'name'
111  *				will be set to point to everything up to but
112  *				not including the first separator on the line.
113  *		BOOLEAN		An entry consisting of a name followed by
114  *				a separator.  'name' will be set to point to
115  *				the name of the capability.
116  *		NUMBER		An entry of the form
117  *					name#digits,
118  *				'name' will be set to point to the capability
119  *				name and 'valnumber' to the number given.
120  *		STRING		An entry of the form
121  *					name=characters,
122  *				'name' is set to the capability name and
123  *				'valstring' to the string of characters, with
124  *				input translations done.
125  *		CANCEL		An entry of the form
126  *					name@,
127  *				'name' is set to the capability name and
128  *				'valnumber' to -1.
129  *		EOF		The end of the file has been reached.
130  *
131  *	A `separator' is either a comma or a semicolon, depending on whether
132  *	we are in termcap or terminfo mode.
133  *
134  */
135 
136 int
137 _nc_get_token(void)
138 {
139     static const char terminfo_punct[] = "@%&*!#";
140     long number;
141     int type;
142     int ch;
143     char *numchk;
144     char numbuf[80];
145     unsigned found;
146     static char buffer[MAX_ENTRY_SIZE];
147     char *ptr;
148     int dot_flag = FALSE;
149     long token_start;
150 
151     if (pushtype != NO_PUSHBACK) {
152 	int retval = pushtype;
153 
154 	_nc_set_type(pushname);
155 	DEBUG(3, ("pushed-back token: `%s', class %d",
156 		  _nc_curr_token.tk_name, pushtype));
157 
158 	pushtype = NO_PUSHBACK;
159 	pushname[0] = '\0';
160 
161 	/* currtok wasn't altered by _nc_push_token() */
162 	return (retval);
163     }
164 
165     if (end_of_stream())
166 	return (EOF);
167 
168   start_token:
169     token_start = stream_pos();
170     while ((ch = next_char()) == '\n' || iswhite(ch))
171 	continue;
172 
173     ch = eat_escaped_newline(ch);
174 
175     if (ch == EOF)
176 	type = EOF;
177     else {
178 	/* if this is a termcap entry, skip a leading separator */
179 	if (separator == ':' && ch == ':')
180 	    ch = next_char();
181 
182 	if (ch == '.'
183 #if NCURSES_EXT_FUNCS
184 	    && !_nc_disable_period
185 #endif
186 	    ) {
187 	    dot_flag = TRUE;
188 	    DEBUG(8, ("dot-flag set"));
189 
190 	    while ((ch = next_char()) == '.' || iswhite(ch))
191 		continue;
192 	}
193 
194 	if (ch == EOF) {
195 	    type = EOF;
196 	    goto end_of_token;
197 	}
198 
199 	/* have to make some punctuation chars legal for terminfo */
200 	if (!isalnum(ch)
201 #if NCURSES_EXT_FUNCS
202 	    && !(ch == '.' && _nc_disable_period)
203 #endif
204 	    && !strchr(terminfo_punct, (char) ch)) {
205 	    _nc_warning("Illegal character (expected alphanumeric or %s) - %s",
206 			terminfo_punct, unctrl(ch));
207 	    _nc_panic_mode(separator);
208 	    goto start_token;
209 	}
210 
211 	ptr = buffer;
212 	*(ptr++) = ch;
213 
214 	if (first_column) {
215 	    char *desc;
216 
217 	    _nc_comment_start = token_start;
218 	    _nc_comment_end = _nc_curr_file_pos;
219 	    _nc_start_line = _nc_curr_line;
220 
221 	    _nc_syntax = ERR;
222 	    while ((ch = next_char()) != '\n') {
223 		if (ch == EOF)
224 		    _nc_err_abort("premature EOF");
225 		else if (ch == ':' && last_char() != ',') {
226 		    _nc_syntax = SYN_TERMCAP;
227 		    separator = ':';
228 		    break;
229 		} else if (ch == ',') {
230 		    _nc_syntax = SYN_TERMINFO;
231 		    separator = ',';
232 		    /*
233 		     * Fall-through here is not an accident.
234 		     * The idea is that if we see a comma, we
235 		     * figure this is terminfo unless we
236 		     * subsequently run into a colon -- but
237 		     * we don't stop looking for that colon until
238 		     * hitting a newline.  This allows commas to
239 		     * be embedded in description fields of
240 		     * either syntax.
241 		     */
242 		    /* FALLTHRU */
243 		} else
244 		    ch = eat_escaped_newline(ch);
245 
246 		*ptr++ = ch;
247 	    }
248 	    ptr[0] = '\0';
249 	    if (_nc_syntax == ERR) {
250 		/*
251 		 * Grrr...what we ought to do here is barf,
252 		 * complaining that the entry is malformed.
253 		 * But because a couple of name fields in the
254 		 * 8.2 termcap file end with |\, we just have
255 		 * to assume it's termcap syntax.
256 		 */
257 		_nc_syntax = SYN_TERMCAP;
258 		separator = ':';
259 	    } else if (_nc_syntax == SYN_TERMINFO) {
260 		/* throw away trailing /, *$/ */
261 		for (--ptr; iswhite(*ptr) || *ptr == ','; ptr--)
262 		    continue;
263 		ptr[1] = '\0';
264 	    }
265 
266 	    /*
267 	     * This is the soonest we have the terminal name
268 	     * fetched.  Set up for following warning messages.
269 	     */
270 	    ptr = strchr(buffer, '|');
271 	    if (ptr == (char *) NULL)
272 		ptr = buffer + strlen(buffer);
273 	    ch = *ptr;
274 	    *ptr = '\0';
275 	    _nc_set_type(buffer);
276 	    *ptr = ch;
277 
278 	    /*
279 	     * Compute the boundary between the aliases and the
280 	     * description field for syntax-checking purposes.
281 	     */
282 	    desc = strrchr(buffer, '|');
283 	    if (desc) {
284 		if (*desc == '\0')
285 		    _nc_warning("empty longname field");
286 		else if (strchr(desc, ' ') == (char *) NULL)
287 		    _nc_warning("older tic versions may treat the description field as an alias");
288 	    }
289 	    if (!desc)
290 		desc = buffer + strlen(buffer);
291 
292 	    /*
293 	     * Whitespace in a name field other than the long name
294 	     * can confuse rdist and some termcap tools.  Slashes
295 	     * are a no-no.  Other special characters can be
296 	     * dangerous due to shell expansion.
297 	     */
298 	    for (ptr = buffer; ptr < desc; ptr++) {
299 		if (isspace(*ptr)) {
300 		    _nc_warning("whitespace in name or alias field");
301 		    break;
302 		} else if (*ptr == '/') {
303 		    _nc_warning("slashes aren't allowed in names or aliases");
304 		    break;
305 		} else if (strchr("$[]!*?", *ptr)) {
306 		    _nc_warning("dubious character `%c' in name or alias field", *ptr);
307 		    break;
308 		}
309 	    }
310 
311 	    ptr = buffer;
312 
313 	    _nc_curr_token.tk_name = buffer;
314 	    type = NAMES;
315 	} else {
316 	    while ((ch = next_char()) != EOF) {
317 		if (!isalnum(ch)) {
318 		    if (_nc_syntax == SYN_TERMINFO) {
319 			if (ch != '_')
320 			    break;
321 		    } else {	/* allow ';' for "k;" */
322 			if (ch != ';')
323 			    break;
324 		    }
325 		}
326 		*(ptr++) = ch;
327 	    }
328 
329 	    *ptr++ = '\0';
330 	    switch (ch) {
331 	    case ',':
332 	    case ':':
333 		if (ch != separator)
334 		    _nc_err_abort("Separator inconsistent with syntax");
335 		_nc_curr_token.tk_name = buffer;
336 		type = BOOLEAN;
337 		break;
338 	    case '@':
339 		if ((ch = next_char()) != separator)
340 		    _nc_warning("Missing separator after `%s', have %s",
341 				buffer, unctrl(ch));
342 		_nc_curr_token.tk_name = buffer;
343 		type = CANCEL;
344 		break;
345 
346 	    case '#':
347 		found = 0;
348 		while (isalnum(ch = next_char())) {
349 		    numbuf[found++] = ch;
350 		    if (found >= sizeof(numbuf) - 1)
351 			break;
352 		}
353 		numbuf[found] = '\0';
354 		number = strtol(numbuf, &numchk, 0);
355 		if (numchk == numbuf)
356 		    _nc_warning("no value given for `%s'", buffer);
357 		if ((*numchk != '\0') || (ch != separator))
358 		    _nc_warning("Missing separator");
359 		_nc_curr_token.tk_name = buffer;
360 		_nc_curr_token.tk_valnumber = number;
361 		type = NUMBER;
362 		break;
363 
364 	    case '=':
365 		ch = _nc_trans_string(ptr, buffer + sizeof(buffer));
366 		if (ch != separator)
367 		    _nc_warning("Missing separator");
368 		_nc_curr_token.tk_name = buffer;
369 		_nc_curr_token.tk_valstring = ptr;
370 		type = STRING;
371 		break;
372 
373 	    case EOF:
374 		type = EOF;
375 		break;
376 	    default:
377 		/* just to get rid of the compiler warning */
378 		type = UNDEF;
379 		_nc_warning("Illegal character - %s", unctrl(ch));
380 	    }
381 	}			/* end else (first_column == FALSE) */
382     }				/* end else (ch != EOF) */
383 
384   end_of_token:
385 
386 #ifdef TRACE
387     if (dot_flag == TRUE)
388 	DEBUG(8, ("Commented out "));
389 
390     if (_nc_tracing >= DEBUG_LEVEL(7)) {
391 	switch (type) {
392 	case BOOLEAN:
393 	    _tracef("Token: Boolean; name='%s'",
394 		    _nc_curr_token.tk_name);
395 	    break;
396 
397 	case NUMBER:
398 	    _tracef("Token: Number;  name='%s', value=%d",
399 		    _nc_curr_token.tk_name,
400 		    _nc_curr_token.tk_valnumber);
401 	    break;
402 
403 	case STRING:
404 	    _tracef("Token: String;  name='%s', value=%s",
405 		    _nc_curr_token.tk_name,
406 		    _nc_visbuf(_nc_curr_token.tk_valstring));
407 	    break;
408 
409 	case CANCEL:
410 	    _tracef("Token: Cancel; name='%s'",
411 		    _nc_curr_token.tk_name);
412 	    break;
413 
414 	case NAMES:
415 
416 	    _tracef("Token: Names; value='%s'",
417 		    _nc_curr_token.tk_name);
418 	    break;
419 
420 	case EOF:
421 	    _tracef("Token: End of file");
422 	    break;
423 
424 	default:
425 	    _nc_warning("Bad token type");
426 	}
427     }
428 #endif
429 
430     if (dot_flag == TRUE)	/* if commented out, use the next one */
431 	type = _nc_get_token();
432 
433     DEBUG(3, ("token: `%s', class %d", _nc_curr_token.tk_name, type));
434 
435     return (type);
436 }
437 
438 /*
439  *	char
440  *	trans_string(ptr)
441  *
442  *	Reads characters using next_char() until encountering a separator, nl,
443  *	or end-of-file.  The returned value is the character which caused
444  *	reading to stop.  The following translations are done on the input:
445  *
446  *		^X  goes to  ctrl-X (i.e. X & 037)
447  *		{\E,\n,\r,\b,\t,\f}  go to
448  *			{ESCAPE,newline,carriage-return,backspace,tab,formfeed}
449  *		{\^,\\}  go to  {carat,backslash}
450  *		\ddd (for ddd = up to three octal digits)  goes to the character ddd
451  *
452  *		\e == \E
453  *		\0 == \200
454  *
455  */
456 
457 char
458 _nc_trans_string(char *ptr, char *last)
459 {
460     int count = 0;
461     int number;
462     int i, c;
463     chtype ch, last_ch = '\0';
464     bool ignored = FALSE;
465     bool long_warning = FALSE;
466 
467     while ((ch = c = next_char()) != (chtype) separator && c != EOF) {
468 	if (ptr == (last - 1))
469 	    break;
470 	if ((_nc_syntax == SYN_TERMCAP) && c == '\n')
471 	    break;
472 	if (ch == '^' && last_ch != '%') {
473 	    ch = c = next_char();
474 	    if (c == EOF)
475 		_nc_err_abort("Premature EOF");
476 
477 	    if (!(is7bits(ch) && isprint(ch))) {
478 		_nc_warning("Illegal ^ character - %s", unctrl(ch));
479 	    }
480 	    if (ch == '?') {
481 		*(ptr++) = '\177';
482 		if (_nc_tracing)
483 		    _nc_warning("Allow ^? as synonym for \\177");
484 	    } else {
485 		if ((ch &= 037) == 0)
486 		    ch = 128;
487 		*(ptr++) = (char) (ch);
488 	    }
489 	} else if (ch == '\\') {
490 	    ch = c = next_char();
491 	    if (c == EOF)
492 		_nc_err_abort("Premature EOF");
493 
494 	    if (ch >= '0' && ch <= '7') {
495 		number = ch - '0';
496 		for (i = 0; i < 2; i++) {
497 		    ch = c = next_char();
498 		    if (c == EOF)
499 			_nc_err_abort("Premature EOF");
500 
501 		    if (c < '0' || c > '7') {
502 			if (isdigit(c)) {
503 			    _nc_warning("Non-octal digit `%c' in \\ sequence", c);
504 			    /* allow the digit; it'll do less harm */
505 			} else {
506 			    push_back((char) c);
507 			    break;
508 			}
509 		    }
510 
511 		    number = number * 8 + c - '0';
512 		}
513 
514 		if (number == 0)
515 		    number = 0200;
516 		*(ptr++) = (char) number;
517 	    } else {
518 		switch (c) {
519 		case 'E':
520 		case 'e':
521 		    *(ptr++) = '\033';
522 		    break;
523 
524 		case 'a':
525 		    *(ptr++) = '\007';
526 		    break;
527 
528 		case 'l':
529 		case 'n':
530 		    *(ptr++) = '\n';
531 		    break;
532 
533 		case 'r':
534 		    *(ptr++) = '\r';
535 		    break;
536 
537 		case 'b':
538 		    *(ptr++) = '\010';
539 		    break;
540 
541 		case 's':
542 		    *(ptr++) = ' ';
543 		    break;
544 
545 		case 'f':
546 		    *(ptr++) = '\014';
547 		    break;
548 
549 		case 't':
550 		    *(ptr++) = '\t';
551 		    break;
552 
553 		case '\\':
554 		    *(ptr++) = '\\';
555 		    break;
556 
557 		case '^':
558 		    *(ptr++) = '^';
559 		    break;
560 
561 		case ',':
562 		    *(ptr++) = ',';
563 		    break;
564 
565 		case ':':
566 		    *(ptr++) = ':';
567 		    break;
568 
569 		case '\n':
570 		    continue;
571 
572 		default:
573 		    _nc_warning("Illegal character %s in \\ sequence",
574 				unctrl(ch));
575 		    *(ptr++) = (char) ch;
576 		}		/* endswitch (ch) */
577 	    }			/* endelse (ch < '0' ||  ch > '7') */
578 	}
579 	/* end else if (ch == '\\') */
580 	else if (ch == '\n' && (_nc_syntax == SYN_TERMINFO)) {
581 	    /* newlines embedded in a terminfo string are ignored */
582 	    ignored = TRUE;
583 	} else {
584 	    *(ptr++) = (char) ch;
585 	}
586 
587 	if (!ignored) {
588 	    last_ch = ch;
589 	    count++;
590 	}
591 	ignored = FALSE;
592 
593 	if (count > MAXCAPLEN && !long_warning) {
594 	    _nc_warning("Very long string found.  Missing separator?");
595 	    long_warning = TRUE;
596 	}
597     }				/* end while */
598 
599     *ptr = '\0';
600 
601     return (ch);
602 }
603 
604 /*
605  *	_nc_push_token()
606  *
607  *	Push a token of given type so that it will be reread by the next
608  *	get_token() call.
609  */
610 
611 void
612 _nc_push_token(int tokclass)
613 {
614     /*
615      * This implementation is kind of bogus, it will fail if we ever do
616      * more than one pushback at a time between get_token() calls.  It
617      * relies on the fact that curr_tok is static storage that nothing
618      * but get_token() touches.
619      */
620     pushtype = tokclass;
621     _nc_get_type(pushname);
622 
623     DEBUG(3, ("pushing token: `%s', class %d",
624 	      _nc_curr_token.tk_name, pushtype));
625 }
626 
627 /*
628  * Panic mode error recovery - skip everything until a "ch" is found.
629  */
630 void
631 _nc_panic_mode(char ch)
632 {
633     int c;
634 
635     for (;;) {
636 	c = next_char();
637 	if (c == ch)
638 	    return;
639 	if (c == EOF)
640 	    return;
641     }
642 }
643 
644 /*****************************************************************************
645  *
646  * Character-stream handling
647  *
648  *****************************************************************************/
649 
650 #define LEXBUFSIZ	1024
651 
652 static char *bufptr;		/* otherwise, the input buffer pointer */
653 static char *bufstart;		/* start of buffer so we can compute offsets */
654 static FILE *yyin;		/* scanner's input file descriptor */
655 
656 /*
657  *	_nc_reset_input()
658  *
659  *	Resets the input-reading routines.  Used on initialization,
660  *	or after a seek has been done.  Exactly one argument must be
661  *	non-null.
662  */
663 
664 void
665 _nc_reset_input(FILE * fp, char *buf)
666 {
667     pushtype = NO_PUSHBACK;
668     pushname[0] = '\0';
669     yyin = fp;
670     bufstart = bufptr = buf;
671     _nc_curr_file_pos = 0L;
672     if (fp != 0)
673 	_nc_curr_line = 0;
674     _nc_curr_col = 0;
675 }
676 
677 /*
678  *	int last_char()
679  *
680  *	Returns the final nonblank character on the current input buffer
681  */
682 static int
683 last_char(void)
684 {
685     size_t len = strlen(bufptr);
686     while (len--) {
687 	if (!isspace(bufptr[len]))
688 	    return bufptr[len];
689     }
690     return 0;
691 }
692 
693 /*
694  *	int next_char()
695  *
696  *	Returns the next character in the input stream.  Comments and leading
697  *	white space are stripped.
698  *
699  *	The global state variable 'firstcolumn' is set TRUE if the character
700  *	returned is from the first column of the input line.
701  *
702  *	The global variable _nc_curr_line is incremented for each new line.
703  *	The global variable _nc_curr_file_pos is set to the file offset of the
704  *	beginning of each line.
705  */
706 
707 static int
708 next_char(void)
709 {
710     if (!yyin) {
711 	if (*bufptr == '\0')
712 	    return (EOF);
713 	if (*bufptr == '\n') {
714 	    _nc_curr_line++;
715 	    _nc_curr_col = 0;
716 	}
717     } else if (!bufptr || !*bufptr) {
718 	/*
719 	 * In theory this could be recoded to do its I/O one
720 	 * character at a time, saving the buffer space.  In
721 	 * practice, this turns out to be quite hard to get
722 	 * completely right.  Try it and see.  If you succeed,
723 	 * don't forget to hack push_back() correspondingly.
724 	 */
725 	static char line[LEXBUFSIZ];
726 	size_t len;
727 
728 	do {
729 	    _nc_curr_file_pos = ftell(yyin);
730 
731 	    if ((bufstart = fgets(line, LEXBUFSIZ, yyin)) != NULL) {
732 		_nc_curr_line++;
733 		_nc_curr_col = 0;
734 	    }
735 	    bufptr = bufstart;
736 	} while
737 	    (bufstart != NULL && line[0] == '#');
738 
739 	if (bufstart == NULL || *bufstart == 0)
740 	    return (EOF);
741 
742 	while (iswhite(*bufptr))
743 	    bufptr++;
744 
745 	/*
746 	 * Treat a trailing <cr><lf> the same as a <newline> so we can read
747 	 * files on OS/2, etc.
748 	 */
749 	if ((len = strlen(bufptr)) > 1) {
750 	    if (bufptr[len - 1] == '\n'
751 		&& bufptr[len - 2] == '\r') {
752 		len--;
753 		bufptr[len - 1] = '\n';
754 		bufptr[len] = '\0';
755 	    }
756 	}
757 
758 	/*
759 	 * If we don't have a trailing newline, it's because the line is simply
760 	 * too long.  Give up.  (FIXME:  We could instead reallocate the line
761 	 * buffer and allow arbitrary-length lines).
762 	 */
763 	if (len == 0 || (bufptr[len - 1] != '\n'))
764 	    return (EOF);
765     }
766 
767     first_column = (bufptr == bufstart);
768 
769     _nc_curr_col++;
770     return (*bufptr++);
771 }
772 
773 static void
774 push_back(char c)
775 /* push a character back onto the input stream */
776 {
777     if (bufptr == bufstart)
778 	_nc_syserr_abort("Can't backspace off beginning of line");
779     *--bufptr = c;
780 }
781 
782 static long
783 stream_pos(void)
784 /* return our current character position in the input stream */
785 {
786     return (yyin ? ftell(yyin) : (bufptr ? bufptr - bufstart : 0));
787 }
788 
789 static bool
790 end_of_stream(void)
791 /* are we at end of input? */
792 {
793     return ((yyin ? feof(yyin) : (bufptr && *bufptr == '\0'))
794 	    ? TRUE : FALSE);
795 }
796 
797 /* comp_scan.c ends here */
798