2 * Copyright (C) 1984-2011 Mark Nudelman
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.
7 * For more information about less, or for information on how to
8 * contact the author, 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.
19 #if MSDOS_COMPILER==WIN32C
26 extern dev_t curr_dev;
27 extern ino_t curr_ino;
30 typedef POSITION BLOCKNUM;
32 public int ignore_eoi;
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".
41 struct bufnode *next, *prev;
42 struct bufnode *hnext, *hprev;
49 unsigned int datasize;
50 unsigned char data[LBUFSIZE];
52 #define bufnode_buf(bn) ((struct buf *) bn)
55 * The file state is maintained in a filestate structure.
56 * A pointer to the filestate is kept in the ifile structure.
58 #define BUFHASH_SIZE 64
60 struct bufnode buflist;
61 struct bufnode hashtbl[BUFHASH_SIZE];
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
81 #define END_OF_CHAIN (&thisfile->buflist)
82 #define END_OF_HCHAIN(h) (&thisfile->hashtbl[h])
83 #define BUFHASH(blk) ((blk) & (BUFHASH_SIZE-1))
86 * Macros to manipulate the list of buffers in thisfile->buflist.
88 #define FOR_BUFS(bn) \
89 for (bn = ch_bufhead; bn != END_OF_CHAIN; bn = bn->next)
92 (bn)->next->prev = (bn)->prev; \
93 (bn)->prev->next = (bn)->next;
95 #define BUF_INS_HEAD(bn) \
96 (bn)->next = ch_bufhead; \
97 (bn)->prev = END_OF_CHAIN; \
98 ch_bufhead->prev = (bn); \
101 #define BUF_INS_TAIL(bn) \
102 (bn)->next = END_OF_CHAIN; \
103 (bn)->prev = ch_buftail; \
104 ch_buftail->next = (bn); \
108 * Macros to manipulate the list of buffers in thisfile->hashtbl[n].
110 #define FOR_BUFS_IN_CHAIN(h,bn) \
111 for (bn = thisfile->hashtbl[h].hnext; \
112 bn != END_OF_HCHAIN(h); bn = bn->hnext)
114 #define BUF_HASH_RM(bn) \
115 (bn)->hnext->hprev = (bn)->hprev; \
116 (bn)->hprev->hnext = (bn)->hnext;
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);
124 static struct filestate *thisfile;
125 static int ch_ungotchar = -1;
126 static int maxbufs = -1;
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;
138 extern char *namelogfile;
141 static int ch_addbuf();
145 * Get the character pointed to by the read pointer.
150 register struct buf *bp;
151 register struct bufnode *bn;
158 if (thisfile == NULL)
162 * Quick check for the common case where
163 * the desired char is in the head buffer.
165 if (ch_bufhead != END_OF_CHAIN)
167 bp = bufnode_buf(ch_bufhead);
168 if (ch_block == bp->block && ch_offset < bp->datasize)
169 return bp->data[ch_offset];
175 * Look for a buffer holding the desired block.
177 h = BUFHASH(ch_block);
178 FOR_BUFS_IN_CHAIN(h, bn)
180 bp = bufnode_buf(bn);
181 if (bp->block == ch_block)
183 if (ch_offset >= bp->datasize)
185 * Need more data in this buffer.
191 if (bn == END_OF_HCHAIN(h))
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.
200 if (ch_buftail == END_OF_CHAIN ||
201 bufnode_buf(ch_buftail)->block != -1)
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.
209 if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
210 (maxbufs < 0 || ch_nbufs < maxbufs))
213 * Allocation failed: turn off autobuf.
218 bp = bufnode_buf(bn);
219 BUF_HASH_RM(bn); /* Remove from old hash chain. */
220 bp->block = ch_block;
222 BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
226 pos = (ch_block * LBUFSIZE) + bp->datasize;
227 if ((len = ch_length()) != NULL_POSITION && pos >= len)
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 "?".
240 if (!(ch_flags & CH_CANSEEK))
242 if (lseek(ch_file, (off_t)pos, SEEK_SET) == BAD_LSEEK)
244 error("seek error", NULL_PARG);
253 * If we read less than a full block, that's ok.
254 * We use partial block and pick up the rest next time.
256 if (ch_ungotchar != -1)
258 bp->data[bp->datasize] = ch_ungotchar;
261 } else if (ch_flags & CH_HELPFILE)
263 bp->data[bp->datasize] = helpdata[ch_fpos];
267 n = iread(ch_file, &bp->data[bp->datasize],
268 (unsigned int)(LBUFSIZE - bp->datasize));
275 #if MSDOS_COMPILER==WIN32C
279 error("read error", NULL_PARG);
287 * If we have a log file, write the new data to it.
289 if (!secure && logfile >= 0 && n > 0)
290 write(logfile, (char *) &bp->data[bp->datasize], n);
297 * If we have read to end of file, set ch_fsize to indicate
298 * the position of the end of file.
306 * We are ignoring EOF.
307 * Wait a while, then try again.
312 parg.p_string = wait_message();
318 #if MSDOS_COMPILER==WIN32C
325 if (follow_mode == FOLLOW_NAME)
327 /* See whether the file's i-number has changed.
328 * If so, force the file to be closed and
331 int r = stat(get_filename(curr_ifile), &st);
332 if (r == 0 && (st.st_ino != curr_ino ||
333 st.st_dev != curr_dev))
335 /* screen_trashed=2 causes
336 * make_display to reopen the file. */
348 if (ch_bufhead != bn)
351 * Move the buffer to the head of the buffer chain.
352 * This orders the buffer chain, most- to least-recently used.
358 * Move to head of hash chain too.
364 if (ch_offset >= bp->datasize)
366 * After all that, we still don't have enough data.
367 * Go back and try again.
371 return (bp->data[ch_offset]);
375 * ch_ungetchar is a rather kludgy and limited way to push
376 * a single char onto an input file descriptor.
382 if (c != -1 && ch_ungotchar != -1)
383 error("ch_ungetchar overrun", NULL_PARG);
390 * If we haven't read all of standard input into it, do that now.
395 static int tried = FALSE;
399 if (!tried && ch_fsize == NULL_POSITION)
402 ierror("Finishing logfile", NULL_PARG);
403 while (ch_forw_get() != EOI)
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.
420 register struct buf *bp;
421 register struct bufnode *bn;
426 nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
427 for (block = 0; block < nblocks; block++)
432 bp = bufnode_buf(bn);
433 if (bp->block == block)
435 write(logfile, (char *) bp->data, bp->datasize);
440 if (!wrote && !warned)
442 error("Warning: log file is incomplete",
452 * Determine if a specific block is currently in one of the buffers.
458 register struct buf *bp;
459 register struct bufnode *bn;
463 FOR_BUFS_IN_CHAIN(h, bn)
465 bp = bufnode_buf(bn);
466 if (bp->block == block)
473 * Seek to a specified position in the file.
474 * Return 0 if successful, non-zero if can't seek there.
478 register POSITION pos;
483 if (thisfile == NULL)
487 if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
490 new_block = pos / LBUFSIZE;
491 if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
495 while (ch_fpos < pos)
497 if (ch_forw_get() == EOI)
507 ch_block = new_block;
508 ch_offset = pos % LBUFSIZE;
513 * Seek to the end of the file.
520 if (thisfile == NULL)
523 if (ch_flags & CH_CANSEEK)
524 ch_fsize = filesize(ch_file);
527 if (len != NULL_POSITION)
528 return (ch_seek(len));
531 * Do it the slow way: read till end of data.
533 while (ch_forw_get() != EOI)
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.
547 register struct bufnode *bn;
548 register struct bufnode *firstbn;
551 * Try a plain ch_seek first.
553 if (ch_seek(ch_zero()) == 0)
557 * Can't get to position 0.
558 * Look thru the buffers for the one closest to position 0.
560 firstbn = ch_bufhead;
561 if (firstbn == END_OF_CHAIN)
565 if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
568 ch_block = bufnode_buf(firstbn)->block;
574 * Return the length of the file, if known.
579 if (thisfile == NULL)
580 return (NULL_POSITION);
582 return (NULL_POSITION);
583 if (ch_flags & CH_HELPFILE)
584 return (size_helpdata);
589 * Return the current position in the file.
594 if (thisfile == NULL)
595 return (NULL_POSITION);
596 return (ch_block * LBUFSIZE) + ch_offset;
600 * Get the current char and post-increment the read pointer.
607 if (thisfile == NULL)
612 if (ch_offset < LBUFSIZE-1)
623 * Pre-decrement the read pointer and get the new current char.
628 if (thisfile == NULL)
636 if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
639 ch_offset = LBUFSIZE-1;
645 * Set max amount of buffer space.
646 * bufspace is in units of 1024 bytes. -1 mean no limit.
649 ch_setbufspace(bufspace)
656 maxbufs = ((bufspace * 1024) + LBUFSIZE-1) / LBUFSIZE;
663 * Flush (discard) any saved file state, including buffer contents.
668 register struct bufnode *bn;
670 if (thisfile == NULL)
673 if (!(ch_flags & CH_CANSEEK))
676 * If input is a pipe, we don't flush buffer contents,
677 * since the contents can't be recovered.
679 ch_fsize = NULL_POSITION;
684 * Initialize all the buffers.
688 bufnode_buf(bn)->block = -1;
692 * Figure out the size of the file, if we can.
694 ch_fsize = filesize(ch_file);
697 * Seek to a known position: the beginning of the file.
700 ch_block = 0; /* ch_fpos / LBUFSIZE; */
701 ch_offset = 0; /* ch_fpos % LBUFSIZE; */
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.
712 ch_fsize = NULL_POSITION;
713 ch_flags &= ~CH_CANSEEK;
717 if (lseek(ch_file, (off_t)0, SEEK_SET) == BAD_LSEEK)
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. }}
724 error("seek error to 0", NULL_PARG);
729 * Allocate a new buffer.
730 * The buffer is added to the tail of the buffer chain.
735 register struct buf *bp;
736 register struct bufnode *bn;
739 * Allocate and initialize a new buffer and link it
740 * onto the tail of the buffer list.
742 bp = (struct buf *) calloc(1, sizeof(struct buf));
762 for (h = 0; h < BUFHASH_SIZE; h++)
764 thisfile->hashtbl[h].hnext = END_OF_HCHAIN(h);
765 thisfile->hashtbl[h].hprev = END_OF_HCHAIN(h);
770 * Delete all buffers for this file.
775 register struct bufnode *bn;
777 while (ch_bufhead != END_OF_CHAIN)
781 free(bufnode_buf(bn));
788 * Is it possible to seek on a file descriptor?
796 if (f == fd0 && !isatty(fd0))
799 * In MS-DOS, pipes are seekable. Check for
800 * standard input, and pretend it is not seekable.
805 return (lseek(f, (off_t)1, SEEK_SET) != BAD_LSEEK);
809 * Initialize file state for a new file.
817 * See if we already have a filestate for this file.
819 thisfile = (struct filestate *) get_filestate(curr_ifile);
820 if (thisfile == NULL)
823 * Allocate and initialize a new filestate.
825 thisfile = (struct filestate *)
826 calloc(1, sizeof(struct filestate));
827 thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
832 thisfile->offset = 0;
834 thisfile->fsize = NULL_POSITION;
838 * Try to seek; set CH_CANSEEK if it works.
840 if ((flags & CH_CANSEEK) && !seekable(f))
841 ch_flags &= ~CH_CANSEEK;
842 set_filestate(curr_ifile, (void *) thisfile);
844 if (thisfile->file == -1)
855 int keepstate = FALSE;
857 if (thisfile == NULL)
860 if (ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE))
863 * We can seek or re-open, so we don't need to keep buffers.
868 if (!(ch_flags & CH_KEEPOPEN))
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.
876 if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
884 * We don't even need to keep the filestate structure.
888 set_filestate(curr_ifile, (void *) NULL);
893 * Return ch_flags for the current file.
898 if (thisfile == NULL)
905 ch_dump(struct filestate *fs)
913 printf(" --no filestate\n");
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)
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)