xref: /freebsd/contrib/less/ch.c (revision c6ec7d31830ab1c80edae95ad5e4b9dba10c47ac)
1 /*
2  * Copyright (C) 1984-2012  Mark Nudelman
3  *
4  * You may distribute under the terms of either the GNU General Public
5  * License or the Less License, as specified in the README file.
6  *
7  * For more information, see the README file.
8  */
9 
10 
11 /*
12  * Low level character input from the input file.
13  * We use these special purpose routines which optimize moving
14  * both forward and backward from the current read pointer.
15  */
16 
17 #include "less.h"
18 #if MSDOS_COMPILER==WIN32C
19 #include <errno.h>
20 #include <windows.h>
21 #endif
22 
23 #if HAVE_STAT_INO
24 #include <sys/stat.h>
25 extern dev_t curr_dev;
26 extern ino_t curr_ino;
27 #endif
28 
29 typedef POSITION BLOCKNUM;
30 
31 public int ignore_eoi;
32 
33 /*
34  * Pool of buffers holding the most recently used blocks of the input file.
35  * The buffer pool is kept as a doubly-linked circular list,
36  * in order from most- to least-recently used.
37  * The circular list is anchored by the file state "thisfile".
38  */
39 struct bufnode {
40 	struct bufnode *next, *prev;
41 	struct bufnode *hnext, *hprev;
42 };
43 
44 #define	LBUFSIZE	8192
45 struct buf {
46 	struct bufnode node;
47 	BLOCKNUM block;
48 	unsigned int datasize;
49 	unsigned char data[LBUFSIZE];
50 };
51 #define bufnode_buf(bn)  ((struct buf *) bn)
52 
53 /*
54  * The file state is maintained in a filestate structure.
55  * A pointer to the filestate is kept in the ifile structure.
56  */
57 #define	BUFHASH_SIZE	64
58 struct filestate {
59 	struct bufnode buflist;
60 	struct bufnode hashtbl[BUFHASH_SIZE];
61 	int file;
62 	int flags;
63 	POSITION fpos;
64 	int nbufs;
65 	BLOCKNUM block;
66 	unsigned int offset;
67 	POSITION fsize;
68 };
69 
70 #define	ch_bufhead	thisfile->buflist.next
71 #define	ch_buftail	thisfile->buflist.prev
72 #define	ch_nbufs	thisfile->nbufs
73 #define	ch_block	thisfile->block
74 #define	ch_offset	thisfile->offset
75 #define	ch_fpos		thisfile->fpos
76 #define	ch_fsize	thisfile->fsize
77 #define	ch_flags	thisfile->flags
78 #define	ch_file		thisfile->file
79 
80 #define	END_OF_CHAIN	(&thisfile->buflist)
81 #define	END_OF_HCHAIN(h) (&thisfile->hashtbl[h])
82 #define BUFHASH(blk)	((blk) & (BUFHASH_SIZE-1))
83 
84 /*
85  * Macros to manipulate the list of buffers in thisfile->buflist.
86  */
87 #define	FOR_BUFS(bn) \
88 	for (bn = ch_bufhead;  bn != END_OF_CHAIN;  bn = bn->next)
89 
90 #define BUF_RM(bn) \
91 	(bn)->next->prev = (bn)->prev; \
92 	(bn)->prev->next = (bn)->next;
93 
94 #define BUF_INS_HEAD(bn) \
95 	(bn)->next = ch_bufhead; \
96 	(bn)->prev = END_OF_CHAIN; \
97 	ch_bufhead->prev = (bn); \
98 	ch_bufhead = (bn);
99 
100 #define BUF_INS_TAIL(bn) \
101 	(bn)->next = END_OF_CHAIN; \
102 	(bn)->prev = ch_buftail; \
103 	ch_buftail->next = (bn); \
104 	ch_buftail = (bn);
105 
106 /*
107  * Macros to manipulate the list of buffers in thisfile->hashtbl[n].
108  */
109 #define	FOR_BUFS_IN_CHAIN(h,bn) \
110 	for (bn = thisfile->hashtbl[h].hnext;  \
111 	     bn != END_OF_HCHAIN(h);  bn = bn->hnext)
112 
113 #define	BUF_HASH_RM(bn) \
114 	(bn)->hnext->hprev = (bn)->hprev; \
115 	(bn)->hprev->hnext = (bn)->hnext;
116 
117 #define	BUF_HASH_INS(bn,h) \
118 	(bn)->hnext = thisfile->hashtbl[h].hnext; \
119 	(bn)->hprev = END_OF_HCHAIN(h); \
120 	thisfile->hashtbl[h].hnext->hprev = (bn); \
121 	thisfile->hashtbl[h].hnext = (bn);
122 
123 static struct filestate *thisfile;
124 static int ch_ungotchar = -1;
125 static int maxbufs = -1;
126 
127 extern int autobuf;
128 extern int sigs;
129 extern int secure;
130 extern int screen_trashed;
131 extern int follow_mode;
132 extern constant char helpdata[];
133 extern constant int size_helpdata;
134 extern IFILE curr_ifile;
135 #if LOGFILE
136 extern int logfile;
137 extern char *namelogfile;
138 #endif
139 
140 static int ch_addbuf();
141 
142 
143 /*
144  * Get the character pointed to by the read pointer.
145  */
146 	int
147 ch_get()
148 {
149 	register struct buf *bp;
150 	register struct bufnode *bn;
151 	register int n;
152 	register int slept;
153 	register int h;
154 	POSITION pos;
155 	POSITION len;
156 
157 	if (thisfile == NULL)
158 		return (EOI);
159 
160 	/*
161 	 * Quick check for the common case where
162 	 * the desired char is in the head buffer.
163 	 */
164 	if (ch_bufhead != END_OF_CHAIN)
165 	{
166 		bp = bufnode_buf(ch_bufhead);
167 		if (ch_block == bp->block && ch_offset < bp->datasize)
168 			return bp->data[ch_offset];
169 	}
170 
171 	slept = FALSE;
172 
173 	/*
174 	 * Look for a buffer holding the desired block.
175 	 */
176 	h = BUFHASH(ch_block);
177 	FOR_BUFS_IN_CHAIN(h, bn)
178 	{
179 		bp = bufnode_buf(bn);
180 		if (bp->block == ch_block)
181 		{
182 			if (ch_offset >= bp->datasize)
183 				/*
184 				 * Need more data in this buffer.
185 				 */
186 				break;
187 			goto found;
188 		}
189 	}
190 	if (bn == END_OF_HCHAIN(h))
191 	{
192 		/*
193 		 * Block is not in a buffer.
194 		 * Take the least recently used buffer
195 		 * and read the desired block into it.
196 		 * If the LRU buffer has data in it,
197 		 * then maybe allocate a new buffer.
198 		 */
199 		if (ch_buftail == END_OF_CHAIN ||
200 			bufnode_buf(ch_buftail)->block != -1)
201 		{
202 			/*
203 			 * There is no empty buffer to use.
204 			 * Allocate a new buffer if:
205 			 * 1. We can't seek on this file and -b is not in effect; or
206 			 * 2. We haven't allocated the max buffers for this file yet.
207 			 */
208 			if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
209 				(maxbufs < 0 || ch_nbufs < maxbufs))
210 				if (ch_addbuf())
211 					/*
212 					 * Allocation failed: turn off autobuf.
213 					 */
214 					autobuf = OPT_OFF;
215 		}
216 		bn = ch_buftail;
217 		bp = bufnode_buf(bn);
218 		BUF_HASH_RM(bn); /* Remove from old hash chain. */
219 		bp->block = ch_block;
220 		bp->datasize = 0;
221 		BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
222 	}
223 
224     read_more:
225 	pos = (ch_block * LBUFSIZE) + bp->datasize;
226 	if ((len = ch_length()) != NULL_POSITION && pos >= len)
227 		/*
228 		 * At end of file.
229 		 */
230 		return (EOI);
231 
232 	if (pos != ch_fpos)
233 	{
234 		/*
235 		 * Not at the correct position: must seek.
236 		 * If input is a pipe, we're in trouble (can't seek on a pipe).
237 		 * Some data has been lost: just return "?".
238 		 */
239 		if (!(ch_flags & CH_CANSEEK))
240 			return ('?');
241 		if (lseek(ch_file, (off_t)pos, SEEK_SET) == BAD_LSEEK)
242 		{
243  			error("seek error", NULL_PARG);
244 			clear_eol();
245 			return (EOI);
246  		}
247  		ch_fpos = pos;
248  	}
249 
250 	/*
251 	 * Read the block.
252 	 * If we read less than a full block, that's ok.
253 	 * We use partial block and pick up the rest next time.
254 	 */
255 	if (ch_ungotchar != -1)
256 	{
257 		bp->data[bp->datasize] = ch_ungotchar;
258 		n = 1;
259 		ch_ungotchar = -1;
260 	} else if (ch_flags & CH_HELPFILE)
261 	{
262 		bp->data[bp->datasize] = helpdata[ch_fpos];
263 		n = 1;
264 	} else
265 	{
266 		n = iread(ch_file, &bp->data[bp->datasize],
267 			(unsigned int)(LBUFSIZE - bp->datasize));
268 	}
269 
270 	if (n == READ_INTR)
271 		return (EOI);
272 	if (n < 0)
273 	{
274 #if MSDOS_COMPILER==WIN32C
275 		if (errno != EPIPE)
276 #endif
277 		{
278 			error("read error", NULL_PARG);
279 			clear_eol();
280 		}
281 		n = 0;
282 	}
283 
284 #if LOGFILE
285 	/*
286 	 * If we have a log file, write the new data to it.
287 	 */
288 	if (!secure && logfile >= 0 && n > 0)
289 		write(logfile, (char *) &bp->data[bp->datasize], n);
290 #endif
291 
292 	ch_fpos += n;
293 	bp->datasize += n;
294 
295 	/*
296 	 * If we have read to end of file, set ch_fsize to indicate
297 	 * the position of the end of file.
298 	 */
299 	if (n == 0)
300 	{
301 		ch_fsize = pos;
302 		if (ignore_eoi)
303 		{
304 			/*
305 			 * We are ignoring EOF.
306 			 * Wait a while, then try again.
307 			 */
308 			if (!slept)
309 			{
310 				PARG parg;
311 				parg.p_string = wait_message();
312 				ierror("%s", &parg);
313 			}
314 #if !MSDOS_COMPILER
315 	 		sleep(1);
316 #else
317 #if MSDOS_COMPILER==WIN32C
318 			Sleep(1000);
319 #endif
320 #endif
321 			slept = TRUE;
322 
323 #if HAVE_STAT_INO
324 			if (follow_mode == FOLLOW_NAME)
325 			{
326 				/* See whether the file's i-number has changed.
327 				 * If so, force the file to be closed and
328 				 * reopened. */
329 				struct stat st;
330 				int r = stat(get_filename(curr_ifile), &st);
331 				if (r == 0 && (st.st_ino != curr_ino ||
332 					st.st_dev != curr_dev))
333 				{
334 					/* screen_trashed=2 causes
335 					 * make_display to reopen the file. */
336 					screen_trashed = 2;
337 					return (EOI);
338 				}
339 			}
340 #endif
341 		}
342 		if (sigs)
343 			return (EOI);
344 	}
345 
346     found:
347 	if (ch_bufhead != bn)
348 	{
349 		/*
350 		 * Move the buffer to the head of the buffer chain.
351 		 * This orders the buffer chain, most- to least-recently used.
352 		 */
353 		BUF_RM(bn);
354 		BUF_INS_HEAD(bn);
355 
356 		/*
357 		 * Move to head of hash chain too.
358 		 */
359 		BUF_HASH_RM(bn);
360 		BUF_HASH_INS(bn, h);
361 	}
362 
363 	if (ch_offset >= bp->datasize)
364 		/*
365 		 * After all that, we still don't have enough data.
366 		 * Go back and try again.
367 		 */
368 		goto read_more;
369 
370 	return (bp->data[ch_offset]);
371 }
372 
373 /*
374  * ch_ungetchar is a rather kludgy and limited way to push
375  * a single char onto an input file descriptor.
376  */
377 	public void
378 ch_ungetchar(c)
379 	int c;
380 {
381 	if (c != -1 && ch_ungotchar != -1)
382 		error("ch_ungetchar overrun", NULL_PARG);
383 	ch_ungotchar = c;
384 }
385 
386 #if LOGFILE
387 /*
388  * Close the logfile.
389  * If we haven't read all of standard input into it, do that now.
390  */
391 	public void
392 end_logfile()
393 {
394 	static int tried = FALSE;
395 
396 	if (logfile < 0)
397 		return;
398 	if (!tried && ch_fsize == NULL_POSITION)
399 	{
400 		tried = TRUE;
401 		ierror("Finishing logfile", NULL_PARG);
402 		while (ch_forw_get() != EOI)
403 			if (ABORT_SIGS())
404 				break;
405 	}
406 	close(logfile);
407 	logfile = -1;
408 	namelogfile = NULL;
409 }
410 
411 /*
412  * Start a log file AFTER less has already been running.
413  * Invoked from the - command; see toggle_option().
414  * Write all the existing buffered data to the log file.
415  */
416 	public void
417 sync_logfile()
418 {
419 	register struct buf *bp;
420 	register struct bufnode *bn;
421 	int warned = FALSE;
422 	BLOCKNUM block;
423 	BLOCKNUM nblocks;
424 
425 	nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
426 	for (block = 0;  block < nblocks;  block++)
427 	{
428 		int wrote = FALSE;
429 		FOR_BUFS(bn)
430 		{
431 			bp = bufnode_buf(bn);
432 			if (bp->block == block)
433 			{
434 				write(logfile, (char *) bp->data, bp->datasize);
435 				wrote = TRUE;
436 				break;
437 			}
438 		}
439 		if (!wrote && !warned)
440 		{
441 			error("Warning: log file is incomplete",
442 				NULL_PARG);
443 			warned = TRUE;
444 		}
445 	}
446 }
447 
448 #endif
449 
450 /*
451  * Determine if a specific block is currently in one of the buffers.
452  */
453 	static int
454 buffered(block)
455 	BLOCKNUM block;
456 {
457 	register struct buf *bp;
458 	register struct bufnode *bn;
459 	register int h;
460 
461 	h = BUFHASH(block);
462 	FOR_BUFS_IN_CHAIN(h, bn)
463 	{
464 		bp = bufnode_buf(bn);
465 		if (bp->block == block)
466 			return (TRUE);
467 	}
468 	return (FALSE);
469 }
470 
471 /*
472  * Seek to a specified position in the file.
473  * Return 0 if successful, non-zero if can't seek there.
474  */
475 	public int
476 ch_seek(pos)
477 	register POSITION pos;
478 {
479 	BLOCKNUM new_block;
480 	POSITION len;
481 
482 	if (thisfile == NULL)
483 		return (0);
484 
485 	len = ch_length();
486 	if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
487 		return (1);
488 
489 	new_block = pos / LBUFSIZE;
490 	if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
491 	{
492 		if (ch_fpos > pos)
493 			return (1);
494 		while (ch_fpos < pos)
495 		{
496 			if (ch_forw_get() == EOI)
497 				return (1);
498 			if (ABORT_SIGS())
499 				return (1);
500 		}
501 		return (0);
502 	}
503 	/*
504 	 * Set read pointer.
505 	 */
506 	ch_block = new_block;
507 	ch_offset = pos % LBUFSIZE;
508 	return (0);
509 }
510 
511 /*
512  * Seek to the end of the file.
513  */
514 	public int
515 ch_end_seek()
516 {
517 	POSITION len;
518 
519 	if (thisfile == NULL)
520 		return (0);
521 
522 	if (ch_flags & CH_CANSEEK)
523 		ch_fsize = filesize(ch_file);
524 
525 	len = ch_length();
526 	if (len != NULL_POSITION)
527 		return (ch_seek(len));
528 
529 	/*
530 	 * Do it the slow way: read till end of data.
531 	 */
532 	while (ch_forw_get() != EOI)
533 		if (ABORT_SIGS())
534 			return (1);
535 	return (0);
536 }
537 
538 /*
539  * Seek to the beginning of the file, or as close to it as we can get.
540  * We may not be able to seek there if input is a pipe and the
541  * beginning of the pipe is no longer buffered.
542  */
543 	public int
544 ch_beg_seek()
545 {
546 	register struct bufnode *bn;
547 	register struct bufnode *firstbn;
548 
549 	/*
550 	 * Try a plain ch_seek first.
551 	 */
552 	if (ch_seek(ch_zero()) == 0)
553 		return (0);
554 
555 	/*
556 	 * Can't get to position 0.
557 	 * Look thru the buffers for the one closest to position 0.
558 	 */
559 	firstbn = ch_bufhead;
560 	if (firstbn == END_OF_CHAIN)
561 		return (1);
562 	FOR_BUFS(bn)
563 	{
564 		if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
565 			firstbn = bn;
566 	}
567 	ch_block = bufnode_buf(firstbn)->block;
568 	ch_offset = 0;
569 	return (0);
570 }
571 
572 /*
573  * Return the length of the file, if known.
574  */
575 	public POSITION
576 ch_length()
577 {
578 	if (thisfile == NULL)
579 		return (NULL_POSITION);
580 	if (ignore_eoi)
581 		return (NULL_POSITION);
582 	if (ch_flags & CH_HELPFILE)
583 		return (size_helpdata);
584 	if (ch_flags & CH_NODATA)
585 		return (0);
586 	return (ch_fsize);
587 }
588 
589 /*
590  * Return the current position in the file.
591  */
592 	public POSITION
593 ch_tell()
594 {
595 	if (thisfile == NULL)
596 		return (NULL_POSITION);
597 	return (ch_block * LBUFSIZE) + ch_offset;
598 }
599 
600 /*
601  * Get the current char and post-increment the read pointer.
602  */
603 	public int
604 ch_forw_get()
605 {
606 	register int c;
607 
608 	if (thisfile == NULL)
609 		return (EOI);
610 	c = ch_get();
611 	if (c == EOI)
612 		return (EOI);
613 	if (ch_offset < LBUFSIZE-1)
614 		ch_offset++;
615 	else
616 	{
617 		ch_block ++;
618 		ch_offset = 0;
619 	}
620 	return (c);
621 }
622 
623 /*
624  * Pre-decrement the read pointer and get the new current char.
625  */
626 	public int
627 ch_back_get()
628 {
629 	if (thisfile == NULL)
630 		return (EOI);
631 	if (ch_offset > 0)
632 		ch_offset --;
633 	else
634 	{
635 		if (ch_block <= 0)
636 			return (EOI);
637 		if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
638 			return (EOI);
639 		ch_block--;
640 		ch_offset = LBUFSIZE-1;
641 	}
642 	return (ch_get());
643 }
644 
645 /*
646  * Set max amount of buffer space.
647  * bufspace is in units of 1024 bytes.  -1 mean no limit.
648  */
649 	public void
650 ch_setbufspace(bufspace)
651 	int bufspace;
652 {
653 	if (bufspace < 0)
654 		maxbufs = -1;
655 	else
656 	{
657 		maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
658 		if (maxbufs < 1)
659 			maxbufs = 1;
660 	}
661 }
662 
663 /*
664  * Flush (discard) any saved file state, including buffer contents.
665  */
666 	public void
667 ch_flush()
668 {
669 	register struct bufnode *bn;
670 
671 	if (thisfile == NULL)
672 		return;
673 
674 	if (!(ch_flags & CH_CANSEEK))
675 	{
676 		/*
677 		 * If input is a pipe, we don't flush buffer contents,
678 		 * since the contents can't be recovered.
679 		 */
680 		ch_fsize = NULL_POSITION;
681 		return;
682 	}
683 
684 	/*
685 	 * Initialize all the buffers.
686 	 */
687 	FOR_BUFS(bn)
688 	{
689 		bufnode_buf(bn)->block = -1;
690 	}
691 
692 	/*
693 	 * Figure out the size of the file, if we can.
694 	 */
695 	ch_fsize = filesize(ch_file);
696 
697 	/*
698 	 * Seek to a known position: the beginning of the file.
699 	 */
700 	ch_fpos = 0;
701 	ch_block = 0; /* ch_fpos / LBUFSIZE; */
702 	ch_offset = 0; /* ch_fpos % LBUFSIZE; */
703 
704 #if 1
705 	/*
706 	 * This is a kludge to workaround a Linux kernel bug: files in
707 	 * /proc have a size of 0 according to fstat() but have readable
708 	 * data.  They are sometimes, but not always, seekable.
709 	 * Force them to be non-seekable here.
710 	 */
711 	if (ch_fsize == 0)
712 	{
713 		ch_fsize = NULL_POSITION;
714 		ch_flags &= ~CH_CANSEEK;
715 	}
716 #endif
717 
718 	if (lseek(ch_file, (off_t)0, SEEK_SET) == BAD_LSEEK)
719 	{
720 		/*
721 		 * Warning only; even if the seek fails for some reason,
722 		 * there's a good chance we're at the beginning anyway.
723 		 * {{ I think this is bogus reasoning. }}
724 		 */
725 		error("seek error to 0", NULL_PARG);
726 	}
727 }
728 
729 /*
730  * Allocate a new buffer.
731  * The buffer is added to the tail of the buffer chain.
732  */
733 	static int
734 ch_addbuf()
735 {
736 	register struct buf *bp;
737 	register struct bufnode *bn;
738 
739 	/*
740 	 * Allocate and initialize a new buffer and link it
741 	 * onto the tail of the buffer list.
742 	 */
743 	bp = (struct buf *) calloc(1, sizeof(struct buf));
744 	if (bp == NULL)
745 		return (1);
746 	ch_nbufs++;
747 	bp->block = -1;
748 	bn = &bp->node;
749 
750 	BUF_INS_TAIL(bn);
751 	BUF_HASH_INS(bn, 0);
752 	return (0);
753 }
754 
755 /*
756  *
757  */
758 	static void
759 init_hashtbl()
760 {
761 	register int h;
762 
763 	for (h = 0;  h < BUFHASH_SIZE;  h++)
764 	{
765 		thisfile->hashtbl[h].hnext = END_OF_HCHAIN(h);
766 		thisfile->hashtbl[h].hprev = END_OF_HCHAIN(h);
767 	}
768 }
769 
770 /*
771  * Delete all buffers for this file.
772  */
773 	static void
774 ch_delbufs()
775 {
776 	register struct bufnode *bn;
777 
778 	while (ch_bufhead != END_OF_CHAIN)
779 	{
780 		bn = ch_bufhead;
781 		BUF_RM(bn);
782 		free(bufnode_buf(bn));
783 	}
784 	ch_nbufs = 0;
785 	init_hashtbl();
786 }
787 
788 /*
789  * Is it possible to seek on a file descriptor?
790  */
791 	public int
792 seekable(f)
793 	int f;
794 {
795 #if MSDOS_COMPILER
796 	extern int fd0;
797 	if (f == fd0 && !isatty(fd0))
798 	{
799 		/*
800 		 * In MS-DOS, pipes are seekable.  Check for
801 		 * standard input, and pretend it is not seekable.
802 		 */
803 		return (0);
804 	}
805 #endif
806 	return (lseek(f, (off_t)1, SEEK_SET) != BAD_LSEEK);
807 }
808 
809 /*
810  * Force EOF to be at the current read position.
811  * This is used after an ignore_eof read, during which the EOF may change.
812  */
813 	public void
814 ch_set_eof()
815 {
816 	ch_fsize = ch_fpos;
817 }
818 
819 
820 /*
821  * Initialize file state for a new file.
822  */
823 	public void
824 ch_init(f, flags)
825 	int f;
826 	int flags;
827 {
828 	/*
829 	 * See if we already have a filestate for this file.
830 	 */
831 	thisfile = (struct filestate *) get_filestate(curr_ifile);
832 	if (thisfile == NULL)
833 	{
834 		/*
835 		 * Allocate and initialize a new filestate.
836 		 */
837 		thisfile = (struct filestate *)
838 				calloc(1, sizeof(struct filestate));
839 		thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
840 		thisfile->nbufs = 0;
841 		thisfile->flags = 0;
842 		thisfile->fpos = 0;
843 		thisfile->block = 0;
844 		thisfile->offset = 0;
845 		thisfile->file = -1;
846 		thisfile->fsize = NULL_POSITION;
847 		ch_flags = flags;
848 		init_hashtbl();
849 		/*
850 		 * Try to seek; set CH_CANSEEK if it works.
851 		 */
852 		if ((flags & CH_CANSEEK) && !seekable(f))
853 			ch_flags &= ~CH_CANSEEK;
854 		set_filestate(curr_ifile, (void *) thisfile);
855 	}
856 	if (thisfile->file == -1)
857 		thisfile->file = f;
858 	ch_flush();
859 }
860 
861 /*
862  * Close a filestate.
863  */
864 	public void
865 ch_close()
866 {
867 	int keepstate = FALSE;
868 
869 	if (thisfile == NULL)
870 		return;
871 
872 	if (ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE))
873 	{
874 		/*
875 		 * We can seek or re-open, so we don't need to keep buffers.
876 		 */
877 		ch_delbufs();
878 	} else
879 		keepstate = TRUE;
880 	if (!(ch_flags & CH_KEEPOPEN))
881 	{
882 		/*
883 		 * We don't need to keep the file descriptor open
884 		 * (because we can re-open it.)
885 		 * But don't really close it if it was opened via popen(),
886 		 * because pclose() wants to close it.
887 		 */
888 		if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
889 			close(ch_file);
890 		ch_file = -1;
891 	} else
892 		keepstate = TRUE;
893 	if (!keepstate)
894 	{
895 		/*
896 		 * We don't even need to keep the filestate structure.
897 		 */
898 		free(thisfile);
899 		thisfile = NULL;
900 		set_filestate(curr_ifile, (void *) NULL);
901 	}
902 }
903 
904 /*
905  * Return ch_flags for the current file.
906  */
907 	public int
908 ch_getflags()
909 {
910 	if (thisfile == NULL)
911 		return (0);
912 	return (ch_flags);
913 }
914 
915 #if 0
916 	public void
917 ch_dump(struct filestate *fs)
918 {
919 	struct buf *bp;
920 	struct bufnode *bn;
921 	unsigned char *s;
922 
923 	if (fs == NULL)
924 	{
925 		printf(" --no filestate\n");
926 		return;
927 	}
928 	printf(" file %d, flags %x, fpos %x, fsize %x, blk/off %x/%x\n",
929 		fs->file, fs->flags, fs->fpos,
930 		fs->fsize, fs->block, fs->offset);
931 	printf(" %d bufs:\n", fs->nbufs);
932 	for (bn = fs->next; bn != &fs->buflist;  bn = bn->next)
933 	{
934 		bp = bufnode_buf(bn);
935 		printf("%x: blk %x, size %x \"",
936 			bp, bp->block, bp->datasize);
937 		for (s = bp->data;  s < bp->data + 30;  s++)
938 			if (*s >= ' ' && *s < 0x7F)
939 				printf("%c", *s);
940 			else
941 				printf(".");
942 		printf("\"\n");
943 	}
944 }
945 #endif
946