8888 loader: rename STAND to _STANDALONE
[unleashed.git] / bin / less / ch.c
blob58f08d3deb1316a1ee8f5677236f4bddf0544535
1 /*
2 * Copyright (C) 1984-2012 Mark Nudelman
3 * Modified for use with illumos by Garrett D'Amore.
4 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
6 * You may distribute under the terms of either the GNU General Public
7 * License or the Less License, as specified in the README file.
9 * For more information, see the README file.
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.
18 #include <sys/stat.h>
20 #include "less.h"
22 extern dev_t curr_dev;
23 extern ino_t curr_ino;
24 extern int less_is_more;
26 typedef off_t BLOCKNUM;
28 int ignore_eoi;
31 * Pool of buffers holding the most recently used blocks of the input file.
32 * The buffer pool is kept as a doubly-linked circular list,
33 * in order from most- to least-recently used.
34 * The circular list is anchored by the file state "thisfile".
36 struct bufnode {
37 struct bufnode *next, *prev;
38 struct bufnode *hnext, *hprev;
41 #define LBUFSIZE 8192
42 struct buf {
43 struct bufnode node;
44 BLOCKNUM block;
45 unsigned int datasize;
46 unsigned char data[LBUFSIZE];
48 #define bufnode_buf(bn) ((struct buf *)bn)
51 * The file state is maintained in a filestate structure.
52 * A pointer to the filestate is kept in the ifile structure.
54 #define BUFHASH_SIZE 64
55 struct filestate {
56 struct bufnode buflist;
57 struct bufnode hashtbl[BUFHASH_SIZE];
58 int file;
59 int flags;
60 off_t fpos;
61 int nbufs;
62 BLOCKNUM block;
63 unsigned int offset;
64 off_t fsize;
67 #define ch_bufhead thisfile->buflist.next
68 #define ch_buftail thisfile->buflist.prev
69 #define ch_nbufs thisfile->nbufs
70 #define ch_block thisfile->block
71 #define ch_offset thisfile->offset
72 #define ch_fpos thisfile->fpos
73 #define ch_fsize thisfile->fsize
74 #define ch_flags thisfile->flags
75 #define ch_file thisfile->file
77 #define END_OF_CHAIN (&thisfile->buflist)
78 #define END_OF_HCHAIN(h) (&thisfile->hashtbl[h])
79 #define BUFHASH(blk) ((blk) & (BUFHASH_SIZE-1))
82 * Macros to manipulate the list of buffers in thisfile->buflist.
84 #define FOR_BUFS(bn) \
85 for ((bn) = ch_bufhead; (bn) != END_OF_CHAIN; (bn) = (bn)->next)
87 #define BUF_RM(bn) \
88 (bn)->next->prev = (bn)->prev; \
89 (bn)->prev->next = (bn)->next;
91 #define BUF_INS_HEAD(bn) \
92 (bn)->next = ch_bufhead; \
93 (bn)->prev = END_OF_CHAIN; \
94 ch_bufhead->prev = (bn); \
95 ch_bufhead = (bn);
97 #define BUF_INS_TAIL(bn) \
98 (bn)->next = END_OF_CHAIN; \
99 (bn)->prev = ch_buftail; \
100 ch_buftail->next = (bn); \
101 ch_buftail = (bn);
104 * Macros to manipulate the list of buffers in thisfile->hashtbl[n].
106 #define FOR_BUFS_IN_CHAIN(h, bn) \
107 for ((bn) = thisfile->hashtbl[h].hnext; \
108 (bn) != END_OF_HCHAIN(h); (bn) = (bn)->hnext)
110 #define BUF_HASH_RM(bn) \
111 (bn)->hnext->hprev = (bn)->hprev; \
112 (bn)->hprev->hnext = (bn)->hnext;
114 #define BUF_HASH_INS(bn, h) \
115 (bn)->hnext = thisfile->hashtbl[h].hnext; \
116 (bn)->hprev = END_OF_HCHAIN(h); \
117 thisfile->hashtbl[h].hnext->hprev = (bn); \
118 thisfile->hashtbl[h].hnext = (bn);
120 static struct filestate *thisfile;
121 static int ch_ungotchar = -1;
122 static int maxbufs = -1;
124 extern int autobuf;
125 extern volatile sig_atomic_t sigs;
126 extern int secure;
127 extern int screen_trashed;
128 extern int follow_mode;
129 extern IFILE curr_ifile;
130 extern int logfile;
131 extern char *namelogfile;
133 static int ch_addbuf(void);
137 * Get the character pointed to by the read pointer.
140 ch_get(void)
142 struct buf *bp;
143 struct bufnode *bn;
144 int n;
145 int slept;
146 int h;
147 off_t pos;
148 off_t len;
150 if (thisfile == NULL)
151 return (EOI);
154 * Quick check for the common case where
155 * the desired char is in the head buffer.
157 if (ch_bufhead != END_OF_CHAIN) {
158 bp = bufnode_buf(ch_bufhead);
159 if (ch_block == bp->block && ch_offset < bp->datasize)
160 return (bp->data[ch_offset]);
163 slept = FALSE;
166 * Look for a buffer holding the desired block.
168 h = BUFHASH(ch_block);
169 FOR_BUFS_IN_CHAIN(h, bn) {
170 bp = bufnode_buf(bn);
171 if (bp->block == ch_block) {
172 if (ch_offset >= bp->datasize)
174 * Need more data in this buffer.
176 break;
177 goto found;
180 if (bn == END_OF_HCHAIN(h)) {
182 * Block is not in a buffer.
183 * Take the least recently used buffer
184 * and read the desired block into it.
185 * If the LRU buffer has data in it,
186 * then maybe allocate a new buffer.
188 if (ch_buftail == END_OF_CHAIN ||
189 bufnode_buf(ch_buftail)->block != -1) {
191 * There is no empty buffer to use.
192 * Allocate a new buffer if:
193 * 1. We can't seek on this file and -b is not in
194 * effect; or
195 * 2. We haven't allocated the max buffers for this
196 * file yet.
198 if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
199 (maxbufs < 0 || ch_nbufs < maxbufs))
200 if (ch_addbuf())
202 * Allocation failed: turn off autobuf.
204 autobuf = OPT_OFF;
206 bn = ch_buftail;
207 bp = bufnode_buf(bn);
208 BUF_HASH_RM(bn); /* Remove from old hash chain. */
209 bp->block = ch_block;
210 bp->datasize = 0;
211 BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
214 read_more:
215 pos = (ch_block * LBUFSIZE) + bp->datasize;
216 if ((len = ch_length()) != -1 && pos >= len)
218 * At end of file.
220 return (EOI);
222 if (pos != ch_fpos) {
224 * Not at the correct position: must seek.
225 * If input is a pipe, we're in trouble (can't seek on a pipe).
226 * Some data has been lost: just return "?".
228 if (!(ch_flags & CH_CANSEEK))
229 return ('?');
230 if (lseek(ch_file, (off_t)pos, SEEK_SET) == (off_t)-1) {
231 error("seek error", NULL);
232 clear_eol();
233 return (EOI);
235 ch_fpos = pos;
239 * Read the block.
240 * If we read less than a full block, that's ok.
241 * We use partial block and pick up the rest next time.
243 if (ch_ungotchar != -1) {
244 bp->data[bp->datasize] = (unsigned char)ch_ungotchar;
245 n = 1;
246 ch_ungotchar = -1;
247 } else {
248 n = iread(ch_file, &bp->data[bp->datasize],
249 (unsigned int)(LBUFSIZE - bp->datasize));
252 if (n == READ_INTR)
253 return (EOI);
254 if (n < 0) {
255 error("read error", NULL);
256 clear_eol();
257 n = 0;
261 * If we have a log file, write the new data to it.
263 if (!secure && logfile >= 0 && n > 0)
264 (void) write(logfile, (char *)&bp->data[bp->datasize], n);
266 ch_fpos += n;
267 bp->datasize += n;
270 * If we have read to end of file, set ch_fsize to indicate
271 * the position of the end of file.
273 if (n == 0) {
274 ch_fsize = pos;
275 if (ignore_eoi) {
277 * We are ignoring EOF.
278 * Wait a while, then try again.
280 if (!slept) {
281 PARG parg;
282 parg.p_string = wait_message();
283 ierror("%s", &parg);
285 sleep(1);
286 slept = TRUE;
288 if (follow_mode == FOLLOW_NAME) {
290 * See whether the file's i-number has changed.
291 * If so, force the file to be closed and
292 * reopened.
294 struct stat st;
295 int r = stat(get_filename(curr_ifile), &st);
296 if (r == 0 && (st.st_ino != curr_ino ||
297 st.st_dev != curr_dev)) {
299 * screen_trashed=2 causes
300 * make_display to reopen the file.
302 screen_trashed = 2;
303 return (EOI);
307 if (sigs)
308 return (EOI);
311 found:
312 if (ch_bufhead != bn) {
314 * Move the buffer to the head of the buffer chain.
315 * This orders the buffer chain, most- to least-recently used.
317 BUF_RM(bn);
318 BUF_INS_HEAD(bn);
321 * Move to head of hash chain too.
323 BUF_HASH_RM(bn);
324 BUF_HASH_INS(bn, h);
327 if (ch_offset >= bp->datasize)
329 * After all that, we still don't have enough data.
330 * Go back and try again.
332 goto read_more;
334 return (bp->data[ch_offset]);
338 * ch_ungetchar is a rather kludgy and limited way to push
339 * a single char onto an input file descriptor.
341 void
342 ch_ungetchar(int c)
344 if (c != -1 && ch_ungotchar != -1)
345 error("ch_ungetchar overrun", NULL);
346 ch_ungotchar = c;
350 * Close the logfile.
351 * If we haven't read all of standard input into it, do that now.
353 void
354 end_logfile(void)
356 static int tried = FALSE;
358 if (logfile < 0)
359 return;
360 if (!tried && ch_fsize == -1) {
361 tried = TRUE;
362 ierror("Finishing logfile", NULL);
363 while (ch_forw_get() != EOI)
364 if (ABORT_SIGS())
365 break;
367 close(logfile);
368 logfile = -1;
369 namelogfile = NULL;
373 * Start a log file AFTER less has already been running.
374 * Invoked from the - command; see toggle_option().
375 * Write all the existing buffered data to the log file.
377 void
378 sync_logfile(void)
380 struct buf *bp;
381 struct bufnode *bn;
382 int warned = FALSE;
383 BLOCKNUM block;
384 BLOCKNUM nblocks;
386 nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
387 for (block = 0; block < nblocks; block++) {
388 int wrote = FALSE;
389 FOR_BUFS(bn) {
390 bp = bufnode_buf(bn);
391 if (bp->block == block) {
392 (void) write(logfile, (char *)bp->data,
393 bp->datasize);
394 wrote = TRUE;
395 break;
398 if (!wrote && !warned) {
399 error("Warning: log file is incomplete", NULL);
400 warned = TRUE;
406 * Determine if a specific block is currently in one of the buffers.
408 static int
409 buffered(BLOCKNUM block)
411 struct buf *bp;
412 struct bufnode *bn;
413 int h;
415 h = BUFHASH(block);
416 FOR_BUFS_IN_CHAIN(h, bn) {
417 bp = bufnode_buf(bn);
418 if (bp->block == block)
419 return (TRUE);
421 return (FALSE);
425 * Seek to a specified position in the file.
426 * Return 0 if successful, non-zero if can't seek there.
429 ch_seek(off_t pos)
431 BLOCKNUM new_block;
432 off_t len;
434 if (thisfile == NULL)
435 return (0);
437 len = ch_length();
438 if (pos < ch_zero() || (len != -1 && pos > len))
439 return (1);
441 new_block = pos / LBUFSIZE;
442 if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos &&
443 !buffered(new_block)) {
444 if (ch_fpos > pos)
445 return (1);
446 while (ch_fpos < pos) {
447 if (ch_forw_get() == EOI)
448 return (1);
449 if (ABORT_SIGS())
450 return (1);
452 return (0);
455 * Set read pointer.
457 ch_block = new_block;
458 ch_offset = pos % LBUFSIZE;
459 return (0);
463 * Seek to the end of the file.
466 ch_end_seek(void)
468 off_t len;
470 if (thisfile == NULL)
471 return (0);
473 if (ch_flags & CH_CANSEEK)
474 ch_fsize = filesize(ch_file);
476 len = ch_length();
477 if (len != -1)
478 return (ch_seek(len));
481 * Do it the slow way: read till end of data.
483 while (ch_forw_get() != EOI)
484 if (ABORT_SIGS())
485 return (1);
486 return (0);
490 * Seek to the beginning of the file, or as close to it as we can get.
491 * We may not be able to seek there if input is a pipe and the
492 * beginning of the pipe is no longer buffered.
495 ch_beg_seek(void)
497 struct bufnode *bn;
498 struct bufnode *firstbn;
501 * Try a plain ch_seek first.
503 if (ch_seek(ch_zero()) == 0)
504 return (0);
507 * Can't get to position 0.
508 * Look thru the buffers for the one closest to position 0.
510 firstbn = ch_bufhead;
511 if (firstbn == END_OF_CHAIN)
512 return (1);
513 FOR_BUFS(bn) {
514 if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
515 firstbn = bn;
517 ch_block = bufnode_buf(firstbn)->block;
518 ch_offset = 0;
519 return (0);
523 * Return the length of the file, if known.
525 off_t
526 ch_length(void)
528 if (thisfile == NULL)
529 return (-1);
530 if (ignore_eoi)
531 return (-1);
532 if (ch_flags & CH_NODATA)
533 return (0);
534 return (ch_fsize);
538 * Return the current position in the file.
540 off_t
541 ch_tell(void)
543 if (thisfile == NULL)
544 return (-1);
545 return ((ch_block * LBUFSIZE) + ch_offset);
549 * Get the current char and post-increment the read pointer.
552 ch_forw_get(void)
554 int c;
556 if (thisfile == NULL)
557 return (EOI);
558 c = ch_get();
559 if (c == EOI)
560 return (EOI);
561 if (ch_offset < LBUFSIZE-1) {
562 ch_offset++;
563 } else {
564 ch_block ++;
565 ch_offset = 0;
567 return (c);
571 * Pre-decrement the read pointer and get the new current char.
574 ch_back_get(void)
576 if (thisfile == NULL)
577 return (EOI);
578 if (ch_offset > 0) {
579 ch_offset --;
580 } else {
581 if (ch_block <= 0)
582 return (EOI);
583 if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
584 return (EOI);
585 ch_block--;
586 ch_offset = LBUFSIZE-1;
588 return (ch_get());
592 * Set max amount of buffer space.
593 * bufspace is in units of 1024 bytes. -1 mean no limit.
595 void
596 ch_setbufspace(int bufspace)
598 if (bufspace < 0) {
599 maxbufs = -1;
600 } else {
601 maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
602 if (maxbufs < 1)
603 maxbufs = 1;
608 * Flush (discard) any saved file state, including buffer contents.
610 void
611 ch_flush(void)
613 struct bufnode *bn;
615 if (thisfile == NULL)
616 return;
618 if (!(ch_flags & CH_CANSEEK)) {
620 * If input is a pipe, we don't flush buffer contents,
621 * since the contents can't be recovered.
623 ch_fsize = -1;
624 return;
628 * Initialize all the buffers.
630 FOR_BUFS(bn) {
631 bufnode_buf(bn)->block = -1;
635 * Figure out the size of the file, if we can.
637 ch_fsize = filesize(ch_file);
640 * Seek to a known position: the beginning of the file.
642 ch_fpos = 0;
643 ch_block = 0; /* ch_fpos / LBUFSIZE; */
644 ch_offset = 0; /* ch_fpos % LBUFSIZE; */
646 #if 1
648 * This is a kludge to workaround a Linux kernel bug: files in
649 * /proc have a size of 0 according to fstat() but have readable
650 * data. They are sometimes, but not always, seekable.
651 * Force them to be non-seekable here.
653 if (ch_fsize == 0) {
654 ch_fsize = -1;
655 ch_flags &= ~CH_CANSEEK;
657 #endif
659 if (lseek(ch_file, (off_t)0, SEEK_SET) == (off_t)-1) {
661 * Warning only; even if the seek fails for some reason,
662 * there's a good chance we're at the beginning anyway.
663 * {{ I think this is bogus reasoning. }}
665 error("seek error to 0", NULL);
670 * Allocate a new buffer.
671 * The buffer is added to the tail of the buffer chain.
673 static int
674 ch_addbuf(void)
676 struct buf *bp;
677 struct bufnode *bn;
680 * Allocate and initialize a new buffer and link it
681 * onto the tail of the buffer list.
683 bp = calloc(1, sizeof (struct buf));
684 if (bp == NULL)
685 return (1);
686 ch_nbufs++;
687 bp->block = -1;
688 bn = &bp->node;
690 BUF_INS_TAIL(bn);
691 BUF_HASH_INS(bn, 0);
692 return (0);
698 static void
699 init_hashtbl(void)
701 int h;
703 for (h = 0; h < BUFHASH_SIZE; h++) {
704 thisfile->hashtbl[h].hnext = END_OF_HCHAIN(h);
705 thisfile->hashtbl[h].hprev = END_OF_HCHAIN(h);
710 * Delete all buffers for this file.
712 static void
713 ch_delbufs(void)
715 struct bufnode *bn;
717 while (ch_bufhead != END_OF_CHAIN) {
718 bn = ch_bufhead;
719 BUF_RM(bn);
720 free(bufnode_buf(bn));
722 ch_nbufs = 0;
723 init_hashtbl();
727 * Is it possible to seek on a file descriptor?
730 seekable(int f)
732 return (lseek(f, (off_t)1, SEEK_SET) != (off_t)-1);
736 * Force EOF to be at the current read position.
737 * This is used after an ignore_eof read, during which the EOF may change.
739 void
740 ch_set_eof(void)
742 ch_fsize = ch_fpos;
747 * Initialize file state for a new file.
749 void
750 ch_init(int f, int flags)
753 * See if we already have a filestate for this file.
755 thisfile = get_filestate(curr_ifile);
756 if (thisfile == NULL) {
758 * Allocate and initialize a new filestate.
760 thisfile = calloc(1, sizeof (struct filestate));
761 thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
762 thisfile->nbufs = 0;
763 thisfile->flags = 0;
764 thisfile->fpos = 0;
765 thisfile->block = 0;
766 thisfile->offset = 0;
767 thisfile->file = -1;
768 thisfile->fsize = -1;
769 ch_flags = flags;
770 init_hashtbl();
772 * Try to seek; set CH_CANSEEK if it works.
774 if ((flags & CH_CANSEEK) && !seekable(f))
775 ch_flags &= ~CH_CANSEEK;
776 set_filestate(curr_ifile, (void *) thisfile);
778 if (thisfile->file == -1)
779 thisfile->file = f;
780 ch_flush();
784 * Close a filestate.
786 void
787 ch_close(void)
789 int keepstate = FALSE;
791 if (thisfile == NULL)
792 return;
794 if (ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE)) {
796 * We can seek or re-open, so we don't need to keep buffers.
798 ch_delbufs();
799 } else {
800 keepstate = TRUE;
802 if (!(ch_flags & CH_KEEPOPEN)) {
804 * We don't need to keep the file descriptor open
805 * (because we can re-open it.)
806 * But don't really close it if it was opened via popen(),
807 * because pclose() wants to close it.
809 if (!(ch_flags & CH_POPENED))
810 close(ch_file);
811 ch_file = -1;
812 } else {
813 keepstate = TRUE;
815 if (!keepstate) {
817 * We don't even need to keep the filestate structure.
819 free(thisfile);
820 thisfile = NULL;
821 set_filestate(curr_ifile, NULL);
826 * Return ch_flags for the current file.
829 ch_getflags(void)
831 if (thisfile == NULL)
832 return (0);
833 return (ch_flags);