ch.c revision 367516 
1/*
2 * Copyright (C) 1984-2020  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>
25extern dev_t curr_dev;
26extern ino_t curr_ino;
27#endif
28
29typedef POSITION BLOCKNUM;
30
31public 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 */
39struct bufnode {
40	struct bufnode *next, *prev;
41	struct bufnode *hnext, *hprev;
42};
43
44#define	LBUFSIZE	8192
45struct 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	1024
58struct 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
123static struct filestate *thisfile;
124static int ch_ungotchar = -1;
125static int maxbufs = -1;
126
127extern int autobuf;
128extern int sigs;
129extern int secure;
130extern int screen_trashed;
131extern int follow_mode;
132extern constant char helpdata[];
133extern constant int size_helpdata;
134extern IFILE curr_ifile;
135#if LOGFILE
136extern int logfile;
137extern char *namelogfile;
138#endif
139
140static int ch_addbuf();
141
142
143/*
144 * Get the character pointed to by the read pointer.
145 */
146	int
147ch_get(VOID_PARAM)
148{
149	struct buf *bp;
150	struct bufnode *bn;
151	int n;
152	int slept;
153	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				 * or the file has shrunk.
328				 * If so, force the file to be closed and
329				 * reopened. */
330				struct stat st;
331				POSITION curr_pos = ch_tell();
332				int r = stat(get_filename(curr_ifile), &st);
333				if (r == 0 && (st.st_ino != curr_ino ||
334					st.st_dev != curr_dev ||
335					(curr_pos != NULL_POSITION && st.st_size < curr_pos)))
336				{
337					/* screen_trashed=2 causes
338					 * make_display to reopen the file. */
339					screen_trashed = 2;
340					return (EOI);
341				}
342			}
343#endif
344		}
345		if (sigs)
346			return (EOI);
347	}
348
349    found:
350	if (ch_bufhead != bn)
351	{
352		/*
353		 * Move the buffer to the head of the buffer chain.
354		 * This orders the buffer chain, most- to least-recently used.
355		 */
356		BUF_RM(bn);
357		BUF_INS_HEAD(bn);
358
359		/*
360		 * Move to head of hash chain too.
361		 */
362		BUF_HASH_RM(bn);
363		BUF_HASH_INS(bn, h);
364	}
365
366	if (ch_offset >= bp->datasize)
367		/*
368		 * After all that, we still don't have enough data.
369		 * Go back and try again.
370		 */
371		goto read_more;
372
373	return (bp->data[ch_offset]);
374}
375
376/*
377 * ch_ungetchar is a rather kludgy and limited way to push
378 * a single char onto an input file descriptor.
379 */
380	public void
381ch_ungetchar(c)
382	int c;
383{
384	if (c != -1 && ch_ungotchar != -1)
385		error("ch_ungetchar overrun", NULL_PARG);
386	ch_ungotchar = c;
387}
388
389#if LOGFILE
390/*
391 * Close the logfile.
392 * If we haven't read all of standard input into it, do that now.
393 */
394	public void
395end_logfile(VOID_PARAM)
396{
397	static int tried = FALSE;
398
399	if (logfile < 0)
400		return;
401	if (!tried && ch_fsize == NULL_POSITION)
402	{
403		tried = TRUE;
404		ierror("Finishing logfile", NULL_PARG);
405		while (ch_forw_get() != EOI)
406			if (ABORT_SIGS())
407				break;
408	}
409	close(logfile);
410	logfile = -1;
411	free(namelogfile);
412	namelogfile = NULL;
413}
414
415/*
416 * Start a log file AFTER less has already been running.
417 * Invoked from the - command; see toggle_option().
418 * Write all the existing buffered data to the log file.
419 */
420	public void
421sync_logfile(VOID_PARAM)
422{
423	struct buf *bp;
424	struct bufnode *bn;
425	int warned = FALSE;
426	BLOCKNUM block;
427	BLOCKNUM nblocks;
428
429	nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
430	for (block = 0;  block < nblocks;  block++)
431	{
432		int wrote = FALSE;
433		FOR_BUFS(bn)
434		{
435			bp = bufnode_buf(bn);
436			if (bp->block == block)
437			{
438				write(logfile, (char *) bp->data, bp->datasize);
439				wrote = TRUE;
440				break;
441			}
442		}
443		if (!wrote && !warned)
444		{
445			error("Warning: log file is incomplete",
446				NULL_PARG);
447			warned = TRUE;
448		}
449	}
450}
451
452#endif
453
454/*
455 * Determine if a specific block is currently in one of the buffers.
456 */
457	static int
458buffered(block)
459	BLOCKNUM block;
460{
461	struct buf *bp;
462	struct bufnode *bn;
463	int h;
464
465	h = BUFHASH(block);
466	FOR_BUFS_IN_CHAIN(h, bn)
467	{
468		bp = bufnode_buf(bn);
469		if (bp->block == block)
470			return (TRUE);
471	}
472	return (FALSE);
473}
474
475/*
476 * Seek to a specified position in the file.
477 * Return 0 if successful, non-zero if can't seek there.
478 */
479	public int
480ch_seek(pos)
481	POSITION pos;
482{
483	BLOCKNUM new_block;
484	POSITION len;
485
486	if (thisfile == NULL)
487		return (0);
488
489	len = ch_length();
490	if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
491		return (1);
492
493	new_block = pos / LBUFSIZE;
494	if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
495	{
496		if (ch_fpos > pos)
497			return (1);
498		while (ch_fpos < pos)
499		{
500			if (ch_forw_get() == EOI)
501				return (1);
502			if (ABORT_SIGS())
503				return (1);
504		}
505		return (0);
506	}
507	/*
508	 * Set read pointer.
509	 */
510	ch_block = new_block;
511	ch_offset = pos % LBUFSIZE;
512	return (0);
513}
514
515/*
516 * Seek to the end of the file.
517 */
518	public int
519ch_end_seek(VOID_PARAM)
520{
521	POSITION len;
522
523	if (thisfile == NULL)
524		return (0);
525
526	if (ch_flags & CH_CANSEEK)
527		ch_fsize = filesize(ch_file);
528
529	len = ch_length();
530	if (len != NULL_POSITION)
531		return (ch_seek(len));
532
533	/*
534	 * Do it the slow way: read till end of data.
535	 */
536	while (ch_forw_get() != EOI)
537		if (ABORT_SIGS())
538			return (1);
539	return (0);
540}
541
542/*
543 * Seek to the last position in the file that is currently buffered.
544 */
545	public int
546ch_end_buffer_seek(VOID_PARAM)
547{
548	struct buf *bp;
549	struct bufnode *bn;
550	POSITION buf_pos;
551	POSITION end_pos;
552
553	if (thisfile == NULL || (ch_flags & CH_CANSEEK))
554		return (ch_end_seek());
555
556	end_pos = 0;
557	FOR_BUFS(bn)
558	{
559		bp = bufnode_buf(bn);
560		buf_pos = (bp->block * LBUFSIZE) + bp->datasize;
561		if (buf_pos > end_pos)
562			end_pos = buf_pos;
563	}
564
565	return (ch_seek(end_pos));
566}
567
568/*
569 * Seek to the beginning of the file, or as close to it as we can get.
570 * We may not be able to seek there if input is a pipe and the
571 * beginning of the pipe is no longer buffered.
572 */
573	public int
574ch_beg_seek(VOID_PARAM)
575{
576	struct bufnode *bn;
577	struct bufnode *firstbn;
578
579	/*
580	 * Try a plain ch_seek first.
581	 */
582	if (ch_seek(ch_zero()) == 0)
583		return (0);
584
585	/*
586	 * Can't get to position 0.
587	 * Look thru the buffers for the one closest to position 0.
588	 */
589	firstbn = ch_bufhead;
590	if (firstbn == END_OF_CHAIN)
591		return (1);
592	FOR_BUFS(bn)
593	{
594		if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
595			firstbn = bn;
596	}
597	ch_block = bufnode_buf(firstbn)->block;
598	ch_offset = 0;
599	return (0);
600}
601
602/*
603 * Return the length of the file, if known.
604 */
605	public POSITION
606ch_length(VOID_PARAM)
607{
608	if (thisfile == NULL)
609		return (NULL_POSITION);
610	if (ignore_eoi)
611		return (NULL_POSITION);
612	if (ch_flags & CH_HELPFILE)
613		return (size_helpdata);
614	if (ch_flags & CH_NODATA)
615		return (0);
616	return (ch_fsize);
617}
618
619/*
620 * Return the current position in the file.
621 */
622	public POSITION
623ch_tell(VOID_PARAM)
624{
625	if (thisfile == NULL)
626		return (NULL_POSITION);
627	return (ch_block * LBUFSIZE) + ch_offset;
628}
629
630/*
631 * Get the current char and post-increment the read pointer.
632 */
633	public int
634ch_forw_get(VOID_PARAM)
635{
636	int c;
637
638	if (thisfile == NULL)
639		return (EOI);
640	c = ch_get();
641	if (c == EOI)
642		return (EOI);
643	if (ch_offset < LBUFSIZE-1)
644		ch_offset++;
645	else
646	{
647		ch_block ++;
648		ch_offset = 0;
649	}
650	return (c);
651}
652
653/*
654 * Pre-decrement the read pointer and get the new current char.
655 */
656	public int
657ch_back_get(VOID_PARAM)
658{
659	if (thisfile == NULL)
660		return (EOI);
661	if (ch_offset > 0)
662		ch_offset --;
663	else
664	{
665		if (ch_block <= 0)
666			return (EOI);
667		if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
668			return (EOI);
669		ch_block--;
670		ch_offset = LBUFSIZE-1;
671	}
672	return (ch_get());
673}
674
675/*
676 * Set max amount of buffer space.
677 * bufspace is in units of 1024 bytes.  -1 mean no limit.
678 */
679	public void
680ch_setbufspace(bufspace)
681	int bufspace;
682{
683	if (bufspace < 0)
684		maxbufs = -1;
685	else
686	{
687		maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
688		if (maxbufs < 1)
689			maxbufs = 1;
690	}
691}
692
693/*
694 * Flush (discard) any saved file state, including buffer contents.
695 */
696	public void
697ch_flush(VOID_PARAM)
698{
699	struct bufnode *bn;
700
701	if (thisfile == NULL)
702		return;
703
704	if (!(ch_flags & CH_CANSEEK))
705	{
706		/*
707		 * If input is a pipe, we don't flush buffer contents,
708		 * since the contents can't be recovered.
709		 */
710		ch_fsize = NULL_POSITION;
711		return;
712	}
713
714	/*
715	 * Initialize all the buffers.
716	 */
717	FOR_BUFS(bn)
718	{
719		bufnode_buf(bn)->block = -1;
720	}
721
722	/*
723	 * Figure out the size of the file, if we can.
724	 */
725	ch_fsize = filesize(ch_file);
726
727	/*
728	 * Seek to a known position: the beginning of the file.
729	 */
730	ch_fpos = 0;
731	ch_block = 0; /* ch_fpos / LBUFSIZE; */
732	ch_offset = 0; /* ch_fpos % LBUFSIZE; */
733
734#if 1
735	/*
736	 * This is a kludge to workaround a Linux kernel bug: files in
737	 * /proc have a size of 0 according to fstat() but have readable
738	 * data.  They are sometimes, but not always, seekable.
739	 * Force them to be non-seekable here.
740	 */
741	if (ch_fsize == 0)
742	{
743		ch_fsize = NULL_POSITION;
744		ch_flags &= ~CH_CANSEEK;
745	}
746#endif
747
748	if (lseek(ch_file, (off_t)0, SEEK_SET) == BAD_LSEEK)
749	{
750		/*
751		 * Warning only; even if the seek fails for some reason,
752		 * there's a good chance we're at the beginning anyway.
753		 * {{ I think this is bogus reasoning. }}
754		 */
755		error("seek error to 0", NULL_PARG);
756	}
757}
758
759/*
760 * Allocate a new buffer.
761 * The buffer is added to the tail of the buffer chain.
762 */
763	static int
764ch_addbuf(VOID_PARAM)
765{
766	struct buf *bp;
767	struct bufnode *bn;
768
769	/*
770	 * Allocate and initialize a new buffer and link it
771	 * onto the tail of the buffer list.
772	 */
773	bp = (struct buf *) calloc(1, sizeof(struct buf));
774	if (bp == NULL)
775		return (1);
776	ch_nbufs++;
777	bp->block = -1;
778	bn = &bp->node;
779
780	BUF_INS_TAIL(bn);
781	BUF_HASH_INS(bn, 0);
782	return (0);
783}
784
785/*
786 *
787 */
788	static void
789init_hashtbl(VOID_PARAM)
790{
791	int h;
792
793	for (h = 0;  h < BUFHASH_SIZE;  h++)
794	{
795		thisfile->hashtbl[h].hnext = END_OF_HCHAIN(h);
796		thisfile->hashtbl[h].hprev = END_OF_HCHAIN(h);
797	}
798}
799
800/*
801 * Delete all buffers for this file.
802 */
803	static void
804ch_delbufs(VOID_PARAM)
805{
806	struct bufnode *bn;
807
808	while (ch_bufhead != END_OF_CHAIN)
809	{
810		bn = ch_bufhead;
811		BUF_RM(bn);
812		free(bufnode_buf(bn));
813	}
814	ch_nbufs = 0;
815	init_hashtbl();
816}
817
818/*
819 * Is it possible to seek on a file descriptor?
820 */
821	public int
822seekable(f)
823	int f;
824{
825#if MSDOS_COMPILER
826	extern int fd0;
827	if (f == fd0 && !isatty(fd0))
828	{
829		/*
830		 * In MS-DOS, pipes are seekable.  Check for
831		 * standard input, and pretend it is not seekable.
832		 */
833		return (0);
834	}
835#endif
836	return (lseek(f, (off_t)1, SEEK_SET) != BAD_LSEEK);
837}
838
839/*
840 * Force EOF to be at the current read position.
841 * This is used after an ignore_eof read, during which the EOF may change.
842 */
843	public void
844ch_set_eof(VOID_PARAM)
845{
846	if (ch_fsize != NULL_POSITION && ch_fsize < ch_fpos)
847		ch_fsize = ch_fpos;
848}
849
850
851/*
852 * Initialize file state for a new file.
853 */
854	public void
855ch_init(f, flags)
856	int f;
857	int flags;
858{
859	/*
860	 * See if we already have a filestate for this file.
861	 */
862	thisfile = (struct filestate *) get_filestate(curr_ifile);
863	if (thisfile == NULL)
864	{
865		/*
866		 * Allocate and initialize a new filestate.
867		 */
868		thisfile = (struct filestate *)
869				calloc(1, sizeof(struct filestate));
870		thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
871		thisfile->nbufs = 0;
872		thisfile->flags = flags;
873		thisfile->fpos = 0;
874		thisfile->block = 0;
875		thisfile->offset = 0;
876		thisfile->file = -1;
877		thisfile->fsize = NULL_POSITION;
878		init_hashtbl();
879		/*
880		 * Try to seek; set CH_CANSEEK if it works.
881		 */
882		if ((flags & CH_CANSEEK) && !seekable(f))
883			ch_flags &= ~CH_CANSEEK;
884		set_filestate(curr_ifile, (void *) thisfile);
885	}
886	if (thisfile->file == -1)
887		thisfile->file = f;
888	ch_flush();
889}
890
891/*
892 * Close a filestate.
893 */
894	public void
895ch_close(VOID_PARAM)
896{
897	int keepstate = FALSE;
898
899	if (thisfile == NULL)
900		return;
901
902	if ((ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE)) && !(ch_flags & CH_KEEPOPEN))
903	{
904		/*
905		 * We can seek or re-open, so we don't need to keep buffers.
906		 */
907		ch_delbufs();
908	} else
909		keepstate = TRUE;
910	if (!(ch_flags & CH_KEEPOPEN))
911	{
912		/*
913		 * We don't need to keep the file descriptor open
914		 * (because we can re-open it.)
915		 * But don't really close it if it was opened via popen(),
916		 * because pclose() wants to close it.
917		 */
918		if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
919			close(ch_file);
920		ch_file = -1;
921	} else
922		keepstate = TRUE;
923	if (!keepstate)
924	{
925		/*
926		 * We don't even need to keep the filestate structure.
927		 */
928		free(thisfile);
929		thisfile = NULL;
930		set_filestate(curr_ifile, (void *) NULL);
931	}
932}
933
934/*
935 * Return ch_flags for the current file.
936 */
937	public int
938ch_getflags(VOID_PARAM)
939{
940	if (thisfile == NULL)
941		return (0);
942	return (ch_flags);
943}
944
945#if 0
946	public void
947ch_dump(struct filestate *fs)
948{
949	struct buf *bp;
950	struct bufnode *bn;
951	unsigned char *s;
952
953	if (fs == NULL)
954	{
955		printf(" --no filestate\n");
956		return;
957	}
958	printf(" file %d, flags %x, fpos %x, fsize %x, blk/off %x/%x\n",
959		fs->file, fs->flags, fs->fpos,
960		fs->fsize, fs->block, fs->offset);
961	printf(" %d bufs:\n", fs->nbufs);
962	for (bn = fs->next; bn != &fs->buflist;  bn = bn->next)
963	{
964		bp = bufnode_buf(bn);
965		printf("%x: blk %x, size %x \"",
966			bp, bp->block, bp->datasize);
967		for (s = bp->data;  s < bp->data + 30;  s++)
968			if (*s >= ' ' && *s < 0x7F)
969				printf("%c", *s);
970			else
971				printf(".");
972		printf("\"\n");
973	}
974}
975#endif
976