xref: /freebsd/contrib/less/ch.c (revision 1670a1c2a47d10ecccd001970b859caf93cd3b6e)
1 /*
2  * Copyright (C) 1984-2009  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 about less, or for information on how to
8  * contact the author, see the README file.
9  */
10 
11 
12 /*
13  * Low level character input from the input file.
14  * We use these special purpose routines which optimize moving
15  * both forward and backward from the current read pointer.
16  */
17 
18 #include "less.h"
19 #if MSDOS_COMPILER==WIN32C
20 #include <errno.h>
21 #include <windows.h>
22 #endif
23 
24 #if HAVE_STAT_INO
25 #include <sys/stat.h>
26 extern dev_t curr_dev;
27 extern ino_t curr_ino;
28 #endif
29 
30 typedef POSITION BLOCKNUM;
31 
32 public int ignore_eoi;
33 
34 /*
35  * Pool of buffers holding the most recently used blocks of the input file.
36  * The buffer pool is kept as a doubly-linked circular list,
37  * in order from most- to least-recently used.
38  * The circular list is anchored by the file state "thisfile".
39  */
40 struct bufnode {
41 	struct bufnode *next, *prev;
42 	struct bufnode *hnext, *hprev;
43 };
44 
45 #define	LBUFSIZE	8192
46 struct buf {
47 	struct bufnode node;
48 	BLOCKNUM block;
49 	unsigned int datasize;
50 	unsigned char data[LBUFSIZE];
51 };
52 #define bufnode_buf(bn)  ((struct buf *) bn)
53 
54 /*
55  * The file state is maintained in a filestate structure.
56  * A pointer to the filestate is kept in the ifile structure.
57  */
58 #define	BUFHASH_SIZE	64
59 struct filestate {
60 	struct bufnode buflist;
61 	struct bufnode hashtbl[BUFHASH_SIZE];
62 	int file;
63 	int flags;
64 	POSITION fpos;
65 	int nbufs;
66 	BLOCKNUM block;
67 	unsigned int offset;
68 	POSITION fsize;
69 };
70 
71 #define	ch_bufhead	thisfile->buflist.next
72 #define	ch_buftail	thisfile->buflist.prev
73 #define	ch_nbufs	thisfile->nbufs
74 #define	ch_block	thisfile->block
75 #define	ch_offset	thisfile->offset
76 #define	ch_fpos		thisfile->fpos
77 #define	ch_fsize	thisfile->fsize
78 #define	ch_flags	thisfile->flags
79 #define	ch_file		thisfile->file
80 
81 #define	END_OF_CHAIN	(&thisfile->buflist)
82 #define	END_OF_HCHAIN(h) (&thisfile->hashtbl[h])
83 #define BUFHASH(blk)	((blk) & (BUFHASH_SIZE-1))
84 
85 /*
86  * Macros to manipulate the list of buffers in thisfile->buflist.
87  */
88 #define	FOR_BUFS(bn) \
89 	for (bn = ch_bufhead;  bn != END_OF_CHAIN;  bn = bn->next)
90 
91 #define BUF_RM(bn) \
92 	(bn)->next->prev = (bn)->prev; \
93 	(bn)->prev->next = (bn)->next;
94 
95 #define BUF_INS_HEAD(bn) \
96 	(bn)->next = ch_bufhead; \
97 	(bn)->prev = END_OF_CHAIN; \
98 	ch_bufhead->prev = (bn); \
99 	ch_bufhead = (bn);
100 
101 #define BUF_INS_TAIL(bn) \
102 	(bn)->next = END_OF_CHAIN; \
103 	(bn)->prev = ch_buftail; \
104 	ch_buftail->next = (bn); \
105 	ch_buftail = (bn);
106 
107 /*
108  * Macros to manipulate the list of buffers in thisfile->hashtbl[n].
109  */
110 #define	FOR_BUFS_IN_CHAIN(h,bn) \
111 	for (bn = thisfile->hashtbl[h].hnext;  \
112 	     bn != END_OF_HCHAIN(h);  bn = bn->hnext)
113 
114 #define	BUF_HASH_RM(bn) \
115 	(bn)->hnext->hprev = (bn)->hprev; \
116 	(bn)->hprev->hnext = (bn)->hnext;
117 
118 #define	BUF_HASH_INS(bn,h) \
119 	(bn)->hnext = thisfile->hashtbl[h].hnext; \
120 	(bn)->hprev = END_OF_HCHAIN(h); \
121 	thisfile->hashtbl[h].hnext->hprev = (bn); \
122 	thisfile->hashtbl[h].hnext = (bn);
123 
124 static struct filestate *thisfile;
125 static int ch_ungotchar = -1;
126 static int maxbufs = -1;
127 
128 extern int autobuf;
129 extern int sigs;
130 extern int secure;
131 extern int screen_trashed;
132 extern int follow_mode;
133 extern constant char helpdata[];
134 extern constant int size_helpdata;
135 extern IFILE curr_ifile;
136 #if LOGFILE
137 extern int logfile;
138 extern char *namelogfile;
139 #endif
140 
141 static int ch_addbuf();
142 
143 
144 /*
145  * Get the character pointed to by the read pointer.
146  */
147 	int
148 ch_get()
149 {
150 	register struct buf *bp;
151 	register struct bufnode *bn;
152 	register int n;
153 	register int slept;
154 	register int h;
155 	POSITION pos;
156 	POSITION len;
157 
158 	if (thisfile == NULL)
159 		return (EOI);
160 
161 	/*
162 	 * Quick check for the common case where
163 	 * the desired char is in the head buffer.
164 	 */
165 	if (ch_bufhead != END_OF_CHAIN)
166 	{
167 		bp = bufnode_buf(ch_bufhead);
168 		if (ch_block == bp->block && ch_offset < bp->datasize)
169 			return bp->data[ch_offset];
170 	}
171 
172 	slept = FALSE;
173 
174 	/*
175 	 * Look for a buffer holding the desired block.
176 	 */
177 	h = BUFHASH(ch_block);
178 	FOR_BUFS_IN_CHAIN(h, bn)
179 	{
180 		bp = bufnode_buf(bn);
181 		if (bp->block == ch_block)
182 		{
183 			if (ch_offset >= bp->datasize)
184 				/*
185 				 * Need more data in this buffer.
186 				 */
187 				break;
188 			goto found;
189 		}
190 	}
191 	if (bn == END_OF_HCHAIN(h))
192 	{
193 		/*
194 		 * Block is not in a buffer.
195 		 * Take the least recently used buffer
196 		 * and read the desired block into it.
197 		 * If the LRU buffer has data in it,
198 		 * then maybe allocate a new buffer.
199 		 */
200 		if (ch_buftail == END_OF_CHAIN ||
201 			bufnode_buf(ch_buftail)->block != -1)
202 		{
203 			/*
204 			 * There is no empty buffer to use.
205 			 * Allocate a new buffer if:
206 			 * 1. We can't seek on this file and -b is not in effect; or
207 			 * 2. We haven't allocated the max buffers for this file yet.
208 			 */
209 			if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
210 				(maxbufs < 0 || ch_nbufs < maxbufs))
211 				if (ch_addbuf())
212 					/*
213 					 * Allocation failed: turn off autobuf.
214 					 */
215 					autobuf = OPT_OFF;
216 		}
217 		bn = ch_buftail;
218 		bp = bufnode_buf(bn);
219 		BUF_HASH_RM(bn); /* Remove from old hash chain. */
220 		bp->block = ch_block;
221 		bp->datasize = 0;
222 		BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
223 	}
224 
225     read_more:
226 	pos = (ch_block * LBUFSIZE) + bp->datasize;
227 	if ((len = ch_length()) != NULL_POSITION && pos >= len)
228 		/*
229 		 * At end of file.
230 		 */
231 		return (EOI);
232 
233 	if (pos != ch_fpos)
234 	{
235 		/*
236 		 * Not at the correct position: must seek.
237 		 * If input is a pipe, we're in trouble (can't seek on a pipe).
238 		 * Some data has been lost: just return "?".
239 		 */
240 		if (!(ch_flags & CH_CANSEEK))
241 			return ('?');
242 		if (lseek(ch_file, (off_t)pos, SEEK_SET) == BAD_LSEEK)
243 		{
244  			error("seek error", NULL_PARG);
245 			clear_eol();
246 			return (EOI);
247  		}
248  		ch_fpos = pos;
249  	}
250 
251 	/*
252 	 * Read the block.
253 	 * If we read less than a full block, that's ok.
254 	 * We use partial block and pick up the rest next time.
255 	 */
256 	if (ch_ungotchar != -1)
257 	{
258 		bp->data[bp->datasize] = ch_ungotchar;
259 		n = 1;
260 		ch_ungotchar = -1;
261 	} else if (ch_flags & CH_HELPFILE)
262 	{
263 		bp->data[bp->datasize] = helpdata[ch_fpos];
264 		n = 1;
265 	} else
266 	{
267 		n = iread(ch_file, &bp->data[bp->datasize],
268 			(unsigned int)(LBUFSIZE - bp->datasize));
269 	}
270 
271 	if (n == READ_INTR)
272 		return (EOI);
273 	if (n < 0)
274 	{
275 #if MSDOS_COMPILER==WIN32C
276 		if (errno != EPIPE)
277 #endif
278 		{
279 			error("read error", NULL_PARG);
280 			clear_eol();
281 		}
282 		n = 0;
283 	}
284 
285 #if LOGFILE
286 	/*
287 	 * If we have a log file, write the new data to it.
288 	 */
289 	if (!secure && logfile >= 0 && n > 0)
290 		write(logfile, (char *) &bp->data[bp->datasize], n);
291 #endif
292 
293 	ch_fpos += n;
294 	bp->datasize += n;
295 
296 	/*
297 	 * If we have read to end of file, set ch_fsize to indicate
298 	 * the position of the end of file.
299 	 */
300 	if (n == 0)
301 	{
302 		ch_fsize = pos;
303 		if (ignore_eoi)
304 		{
305 			/*
306 			 * We are ignoring EOF.
307 			 * Wait a while, then try again.
308 			 */
309 			if (!slept)
310 			{
311 				PARG parg;
312 				parg.p_string = wait_message();
313 				ierror("%s", &parg);
314 			}
315 #if !MSDOS_COMPILER
316 	 		sleep(1);
317 #else
318 #if MSDOS_COMPILER==WIN32C
319 			Sleep(1000);
320 #endif
321 #endif
322 			slept = TRUE;
323 
324 #if HAVE_STAT_INO
325 			if (follow_mode == FOLLOW_NAME)
326 			{
327 				/* See whether the file's i-number has changed.
328 				 * If so, force the file to be closed and
329 				 * reopened. */
330 				struct stat st;
331 				int r = stat(get_filename(curr_ifile), &st);
332 				if (r == 0 && (st.st_ino != curr_ino ||
333 					st.st_dev != curr_dev))
334 				{
335 					/* screen_trashed=2 causes
336 					 * make_display to reopen the file. */
337 					screen_trashed = 2;
338 					return (EOI);
339 				}
340 			}
341 #endif
342 		}
343 		if (sigs)
344 			return (EOI);
345 	}
346 
347     found:
348 	if (ch_bufhead != bn)
349 	{
350 		/*
351 		 * Move the buffer to the head of the buffer chain.
352 		 * This orders the buffer chain, most- to least-recently used.
353 		 */
354 		BUF_RM(bn);
355 		BUF_INS_HEAD(bn);
356 
357 		/*
358 		 * Move to head of hash chain too.
359 		 */
360 		BUF_HASH_RM(bn);
361 		BUF_HASH_INS(bn, h);
362 	}
363 
364 	if (ch_offset >= bp->datasize)
365 		/*
366 		 * After all that, we still don't have enough data.
367 		 * Go back and try again.
368 		 */
369 		goto read_more;
370 
371 	return (bp->data[ch_offset]);
372 }
373 
374 /*
375  * ch_ungetchar is a rather kludgy and limited way to push
376  * a single char onto an input file descriptor.
377  */
378 	public void
379 ch_ungetchar(c)
380 	int c;
381 {
382 	if (c != -1 && ch_ungotchar != -1)
383 		error("ch_ungetchar overrun", NULL_PARG);
384 	ch_ungotchar = c;
385 }
386 
387 #if LOGFILE
388 /*
389  * Close the logfile.
390  * If we haven't read all of standard input into it, do that now.
391  */
392 	public void
393 end_logfile()
394 {
395 	static int tried = FALSE;
396 
397 	if (logfile < 0)
398 		return;
399 	if (!tried && ch_fsize == NULL_POSITION)
400 	{
401 		tried = TRUE;
402 		ierror("Finishing logfile", NULL_PARG);
403 		while (ch_forw_get() != EOI)
404 			if (ABORT_SIGS())
405 				break;
406 	}
407 	close(logfile);
408 	logfile = -1;
409 	namelogfile = NULL;
410 }
411 
412 /*
413  * Start a log file AFTER less has already been running.
414  * Invoked from the - command; see toggle_option().
415  * Write all the existing buffered data to the log file.
416  */
417 	public void
418 sync_logfile()
419 {
420 	register struct buf *bp;
421 	register struct bufnode *bn;
422 	int warned = FALSE;
423 	BLOCKNUM block;
424 	BLOCKNUM nblocks;
425 
426 	nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
427 	for (block = 0;  block < nblocks;  block++)
428 	{
429 		int wrote = FALSE;
430 		FOR_BUFS(bn)
431 		{
432 			bp = bufnode_buf(bn);
433 			if (bp->block == block)
434 			{
435 				write(logfile, (char *) bp->data, bp->datasize);
436 				wrote = TRUE;
437 				break;
438 			}
439 		}
440 		if (!wrote && !warned)
441 		{
442 			error("Warning: log file is incomplete",
443 				NULL_PARG);
444 			warned = TRUE;
445 		}
446 	}
447 }
448 
449 #endif
450 
451 /*
452  * Determine if a specific block is currently in one of the buffers.
453  */
454 	static int
455 buffered(block)
456 	BLOCKNUM block;
457 {
458 	register struct buf *bp;
459 	register struct bufnode *bn;
460 	register int h;
461 
462 	h = BUFHASH(block);
463 	FOR_BUFS_IN_CHAIN(h, bn)
464 	{
465 		bp = bufnode_buf(bn);
466 		if (bp->block == block)
467 			return (TRUE);
468 	}
469 	return (FALSE);
470 }
471 
472 /*
473  * Seek to a specified position in the file.
474  * Return 0 if successful, non-zero if can't seek there.
475  */
476 	public int
477 ch_seek(pos)
478 	register POSITION pos;
479 {
480 	BLOCKNUM new_block;
481 	POSITION len;
482 
483 	if (thisfile == NULL)
484 		return (0);
485 
486 	len = ch_length();
487 	if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
488 		return (1);
489 
490 	new_block = pos / LBUFSIZE;
491 	if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
492 	{
493 		if (ch_fpos > pos)
494 			return (1);
495 		while (ch_fpos < pos)
496 		{
497 			if (ch_forw_get() == EOI)
498 				return (1);
499 			if (ABORT_SIGS())
500 				return (1);
501 		}
502 		return (0);
503 	}
504 	/*
505 	 * Set read pointer.
506 	 */
507 	ch_block = new_block;
508 	ch_offset = pos % LBUFSIZE;
509 	return (0);
510 }
511 
512 /*
513  * Seek to the end of the file.
514  */
515 	public int
516 ch_end_seek()
517 {
518 	POSITION len;
519 
520 	if (thisfile == NULL)
521 		return (0);
522 
523 	if (ch_flags & CH_CANSEEK)
524 		ch_fsize = filesize(ch_file);
525 
526 	len = ch_length();
527 	if (len != NULL_POSITION)
528 		return (ch_seek(len));
529 
530 	/*
531 	 * Do it the slow way: read till end of data.
532 	 */
533 	while (ch_forw_get() != EOI)
534 		if (ABORT_SIGS())
535 			return (1);
536 	return (0);
537 }
538 
539 /*
540  * Seek to the beginning of the file, or as close to it as we can get.
541  * We may not be able to seek there if input is a pipe and the
542  * beginning of the pipe is no longer buffered.
543  */
544 	public int
545 ch_beg_seek()
546 {
547 	register struct bufnode *bn;
548 	register struct bufnode *firstbn;
549 
550 	/*
551 	 * Try a plain ch_seek first.
552 	 */
553 	if (ch_seek(ch_zero()) == 0)
554 		return (0);
555 
556 	/*
557 	 * Can't get to position 0.
558 	 * Look thru the buffers for the one closest to position 0.
559 	 */
560 	firstbn = ch_bufhead;
561 	if (firstbn == END_OF_CHAIN)
562 		return (1);
563 	FOR_BUFS(bn)
564 	{
565 		if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
566 			firstbn = bn;
567 	}
568 	ch_block = bufnode_buf(firstbn)->block;
569 	ch_offset = 0;
570 	return (0);
571 }
572 
573 /*
574  * Return the length of the file, if known.
575  */
576 	public POSITION
577 ch_length()
578 {
579 	if (thisfile == NULL)
580 		return (NULL_POSITION);
581 	if (ignore_eoi)
582 		return (NULL_POSITION);
583 	if (ch_flags & CH_HELPFILE)
584 		return (size_helpdata);
585 	return (ch_fsize);
586 }
587 
588 /*
589  * Return the current position in the file.
590  */
591 	public POSITION
592 ch_tell()
593 {
594 	if (thisfile == NULL)
595 		return (NULL_POSITION);
596 	return (ch_block * LBUFSIZE) + ch_offset;
597 }
598 
599 /*
600  * Get the current char and post-increment the read pointer.
601  */
602 	public int
603 ch_forw_get()
604 {
605 	register int c;
606 
607 	if (thisfile == NULL)
608 		return (EOI);
609 	c = ch_get();
610 	if (c == EOI)
611 		return (EOI);
612 	if (ch_offset < LBUFSIZE-1)
613 		ch_offset++;
614 	else
615 	{
616 		ch_block ++;
617 		ch_offset = 0;
618 	}
619 	return (c);
620 }
621 
622 /*
623  * Pre-decrement the read pointer and get the new current char.
624  */
625 	public int
626 ch_back_get()
627 {
628 	if (thisfile == NULL)
629 		return (EOI);
630 	if (ch_offset > 0)
631 		ch_offset --;
632 	else
633 	{
634 		if (ch_block <= 0)
635 			return (EOI);
636 		if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
637 			return (EOI);
638 		ch_block--;
639 		ch_offset = LBUFSIZE-1;
640 	}
641 	return (ch_get());
642 }
643 
644 /*
645  * Set max amount of buffer space.
646  * bufspace is in units of 1024 bytes.  -1 mean no limit.
647  */
648 	public void
649 ch_setbufspace(bufspace)
650 	int bufspace;
651 {
652 	if (bufspace < 0)
653 		maxbufs = -1;
654 	else
655 	{
656 		maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
657 		if (maxbufs < 1)
658 			maxbufs = 1;
659 	}
660 }
661 
662 /*
663  * Flush (discard) any saved file state, including buffer contents.
664  */
665 	public void
666 ch_flush()
667 {
668 	register struct bufnode *bn;
669 
670 	if (thisfile == NULL)
671 		return;
672 
673 	if (!(ch_flags & CH_CANSEEK))
674 	{
675 		/*
676 		 * If input is a pipe, we don't flush buffer contents,
677 		 * since the contents can't be recovered.
678 		 */
679 		ch_fsize = NULL_POSITION;
680 		return;
681 	}
682 
683 	/*
684 	 * Initialize all the buffers.
685 	 */
686 	FOR_BUFS(bn)
687 	{
688 		bufnode_buf(bn)->block = -1;
689 	}
690 
691 	/*
692 	 * Figure out the size of the file, if we can.
693 	 */
694 	ch_fsize = filesize(ch_file);
695 
696 	/*
697 	 * Seek to a known position: the beginning of the file.
698 	 */
699 	ch_fpos = 0;
700 	ch_block = 0; /* ch_fpos / LBUFSIZE; */
701 	ch_offset = 0; /* ch_fpos % LBUFSIZE; */
702 
703 #if 1
704 	/*
705 	 * This is a kludge to workaround a Linux kernel bug: files in
706 	 * /proc have a size of 0 according to fstat() but have readable
707 	 * data.  They are sometimes, but not always, seekable.
708 	 * Force them to be non-seekable here.
709 	 */
710 	if (ch_fsize == 0)
711 	{
712 		ch_fsize = NULL_POSITION;
713 		ch_flags &= ~CH_CANSEEK;
714 	}
715 #endif
716 
717 	if (lseek(ch_file, (off_t)0, SEEK_SET) == BAD_LSEEK)
718 	{
719 		/*
720 		 * Warning only; even if the seek fails for some reason,
721 		 * there's a good chance we're at the beginning anyway.
722 		 * {{ I think this is bogus reasoning. }}
723 		 */
724 		error("seek error to 0", NULL_PARG);
725 	}
726 }
727 
728 /*
729  * Allocate a new buffer.
730  * The buffer is added to the tail of the buffer chain.
731  */
732 	static int
733 ch_addbuf()
734 {
735 	register struct buf *bp;
736 	register struct bufnode *bn;
737 
738 	/*
739 	 * Allocate and initialize a new buffer and link it
740 	 * onto the tail of the buffer list.
741 	 */
742 	bp = (struct buf *) calloc(1, sizeof(struct buf));
743 	if (bp == NULL)
744 		return (1);
745 	ch_nbufs++;
746 	bp->block = -1;
747 	bn = &bp->node;
748 
749 	BUF_INS_TAIL(bn);
750 	BUF_HASH_INS(bn, 0);
751 	return (0);
752 }
753 
754 /*
755  *
756  */
757 	static void
758 init_hashtbl()
759 {
760 	register int h;
761 
762 	for (h = 0;  h < BUFHASH_SIZE;  h++)
763 	{
764 		thisfile->hashtbl[h].hnext = END_OF_HCHAIN(h);
765 		thisfile->hashtbl[h].hprev = END_OF_HCHAIN(h);
766 	}
767 }
768 
769 /*
770  * Delete all buffers for this file.
771  */
772 	static void
773 ch_delbufs()
774 {
775 	register struct bufnode *bn;
776 
777 	while (ch_bufhead != END_OF_CHAIN)
778 	{
779 		bn = ch_bufhead;
780 		BUF_RM(bn);
781 		free(bufnode_buf(bn));
782 	}
783 	ch_nbufs = 0;
784 	init_hashtbl();
785 }
786 
787 /*
788  * Is it possible to seek on a file descriptor?
789  */
790 	public int
791 seekable(f)
792 	int f;
793 {
794 #if MSDOS_COMPILER
795 	extern int fd0;
796 	if (f == fd0 && !isatty(fd0))
797 	{
798 		/*
799 		 * In MS-DOS, pipes are seekable.  Check for
800 		 * standard input, and pretend it is not seekable.
801 		 */
802 		return (0);
803 	}
804 #endif
805 	return (lseek(f, (off_t)1, SEEK_SET) != BAD_LSEEK);
806 }
807 
808 /*
809  * Initialize file state for a new file.
810  */
811 	public void
812 ch_init(f, flags)
813 	int f;
814 	int flags;
815 {
816 	/*
817 	 * See if we already have a filestate for this file.
818 	 */
819 	thisfile = (struct filestate *) get_filestate(curr_ifile);
820 	if (thisfile == NULL)
821 	{
822 		/*
823 		 * Allocate and initialize a new filestate.
824 		 */
825 		thisfile = (struct filestate *)
826 				calloc(1, sizeof(struct filestate));
827 		thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
828 		thisfile->nbufs = 0;
829 		thisfile->flags = 0;
830 		thisfile->fpos = 0;
831 		thisfile->block = 0;
832 		thisfile->offset = 0;
833 		thisfile->file = -1;
834 		thisfile->fsize = NULL_POSITION;
835 		ch_flags = flags;
836 		init_hashtbl();
837 		/*
838 		 * Try to seek; set CH_CANSEEK if it works.
839 		 */
840 		if ((flags & CH_CANSEEK) && !seekable(f))
841 			ch_flags &= ~CH_CANSEEK;
842 		set_filestate(curr_ifile, (void *) thisfile);
843 	}
844 	if (thisfile->file == -1)
845 		thisfile->file = f;
846 	ch_flush();
847 }
848 
849 /*
850  * Close a filestate.
851  */
852 	public void
853 ch_close()
854 {
855 	int keepstate = FALSE;
856 
857 	if (thisfile == NULL)
858 		return;
859 
860 	if (ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE))
861 	{
862 		/*
863 		 * We can seek or re-open, so we don't need to keep buffers.
864 		 */
865 		ch_delbufs();
866 	} else
867 		keepstate = TRUE;
868 	if (!(ch_flags & CH_KEEPOPEN))
869 	{
870 		/*
871 		 * We don't need to keep the file descriptor open
872 		 * (because we can re-open it.)
873 		 * But don't really close it if it was opened via popen(),
874 		 * because pclose() wants to close it.
875 		 */
876 		if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
877 			close(ch_file);
878 		ch_file = -1;
879 	} else
880 		keepstate = TRUE;
881 	if (!keepstate)
882 	{
883 		/*
884 		 * We don't even need to keep the filestate structure.
885 		 */
886 		free(thisfile);
887 		thisfile = NULL;
888 		set_filestate(curr_ifile, (void *) NULL);
889 	}
890 }
891 
892 /*
893  * Return ch_flags for the current file.
894  */
895 	public int
896 ch_getflags()
897 {
898 	if (thisfile == NULL)
899 		return (0);
900 	return (ch_flags);
901 }
902 
903 #if 0
904 	public void
905 ch_dump(struct filestate *fs)
906 {
907 	struct buf *bp;
908 	struct bufnode *bn;
909 	unsigned char *s;
910 
911 	if (fs == NULL)
912 	{
913 		printf(" --no filestate\n");
914 		return;
915 	}
916 	printf(" file %d, flags %x, fpos %x, fsize %x, blk/off %x/%x\n",
917 		fs->file, fs->flags, fs->fpos,
918 		fs->fsize, fs->block, fs->offset);
919 	printf(" %d bufs:\n", fs->nbufs);
920 	for (bn = fs->next; bn != &fs->buflist;  bn = bn->next)
921 	{
922 		bp = bufnode_buf(bn);
923 		printf("%x: blk %x, size %x \"",
924 			bp, bp->block, bp->datasize);
925 		for (s = bp->data;  s < bp->data + 30;  s++)
926 			if (*s >= ' ' && *s < 0x7F)
927 				printf("%c", *s);
928 			else
929 				printf(".");
930 		printf("\"\n");
931 	}
932 }
933 #endif
934