/*
* Copyright (C) 1984-2023 Mark Nudelman
*
* You may distribute under the terms of either the GNU General Public
* License or the Less License, as specified in the README file.
*
* For more information, see the README file.
*/
/*
* Low level character input from the input file.
* We use these special purpose routines which optimize moving
* both forward and backward from the current read pointer.
*/
/*
* Pool of buffers holding the most recently used blocks of the input file.
* The buffer pool is kept as a doubly-linked circular list,
* in order from most- to least-recently used.
* The circular list is anchored by the file state "thisfile".
*/
struct bufnode {
struct bufnode *next, *prev;
struct bufnode *hnext, *hprev;
};
/*
* The file state is maintained in a filestate structure.
* A pointer to the filestate is kept in the ifile structure.
*/
#define BUFHASH_SIZE 1024
struct filestate {
struct bufnode buflist;
struct bufnode hashtbl[BUFHASH_SIZE];
int file;
int flags;
POSITION fpos;
int nbufs;
BLOCKNUM block;
unsigned int offset;
POSITION fsize;
};
/*
* Macros to manipulate the list of buffers in thisfile->hashtbl[n].
*/
#define FOR_BUFS_IN_CHAIN(h,bn) \
for (bn = thisfile->hashtbl[h].hnext; \
bn != END_OF_HCHAIN(h); bn = bn->hnext)
static struct filestate *thisfile;
static int ch_ungotchar = -1;
static int maxbufs = -1;
extern int autobuf;
extern int sigs;
extern int secure;
extern int screen_trashed;
extern int follow_mode;
extern int waiting_for_data;
extern constant char helpdata[];
extern constant int size_helpdata;
extern IFILE curr_ifile;
#if LOGFILE
extern int logfile;
extern char *namelogfile;
#endif
static int ch_addbuf(void);
/*
* Get the character pointed to by the read pointer.
*/
static int ch_get(void)
{
struct buf *bp;
struct bufnode *bn;
int n;
int read_again;
int h;
POSITION pos;
POSITION len;
if (thisfile == NULL)
return (EOI);
/*
* Quick check for the common case where
* the desired char is in the head buffer.
*/
if (ch_bufhead != END_OF_CHAIN)
{
bp = bufnode_buf(ch_bufhead);
if (ch_block == bp->block && ch_offset < bp->datasize)
return bp->data[ch_offset];
}
/*
* Look for a buffer holding the desired block.
*/
waiting_for_data = FALSE;
h = BUFHASH(ch_block);
FOR_BUFS_IN_CHAIN(h, bn)
{
bp = bufnode_buf(bn);
if (bp->block == ch_block)
{
if (ch_offset >= bp->datasize)
/*
* Need more data in this buffer.
*/
break;
goto found;
}
}
if (bn == END_OF_HCHAIN(h))
{
/*
* Block is not in a buffer.
* Take the least recently used buffer
* and read the desired block into it.
* If the LRU buffer has data in it,
* then maybe allocate a new buffer.
*/
if (ch_buftail == END_OF_CHAIN ||
bufnode_buf(ch_buftail)->block != -1)
{
/*
* There is no empty buffer to use.
* Allocate a new buffer if:
* 1. We can't seek on this file and -b is not in effect; or
* 2. We haven't allocated the max buffers for this file yet.
*/
if ((autobuf && !(ch_flags & CH_CANSEEK)) ||
(maxbufs < 0 || ch_nbufs < maxbufs))
if (ch_addbuf())
/*
* Allocation failed: turn off autobuf.
*/
autobuf = OPT_OFF;
}
bn = ch_buftail;
bp = bufnode_buf(bn);
BUF_HASH_RM(bn); /* Remove from old hash chain. */
bp->block = ch_block;
bp->datasize = 0;
BUF_HASH_INS(bn, h); /* Insert into new hash chain. */
}
for (;;)
{
pos = (ch_block * LBUFSIZE) + bp->datasize;
if ((len = ch_length()) != NULL_POSITION && pos >= len)
/*
* At end of file.
*/
return (EOI);
if (pos != ch_fpos)
{
/*
* Not at the correct position: must seek.
* If input is a pipe, we're in trouble (can't seek on a pipe).
* Some data has been lost: just return "?".
*/
if (!(ch_flags & CH_CANSEEK))
return ('?');
if (lseek(ch_file, (off_t)pos, SEEK_SET) == BAD_LSEEK)
{
error("seek error", NULL_PARG);
clear_eol();
return (EOI);
}
ch_fpos = pos;
}
/*
* Read the block.
* If we read less than a full block, that's ok.
* We use partial block and pick up the rest next time.
*/
if (ch_ungotchar != -1)
{
bp->data[bp->datasize] = ch_ungotchar;
n = 1;
ch_ungotchar = -1;
} else if (ch_flags & CH_HELPFILE)
{
bp->data[bp->datasize] = helpdata[ch_fpos];
n = 1;
} else
{
n = iread(ch_file, &bp->data[bp->datasize],
(unsigned int)(LBUFSIZE - bp->datasize));
}
read_again = FALSE;
if (n == READ_INTR)
{
ch_fsize = pos;
return (EOI);
}
if (n == READ_AGAIN)
{
read_again = TRUE;
n = 0;
}
if (n < 0)
{
#if MSDOS_COMPILER==WIN32C
if (errno != EPIPE)
#endif
{
error("read error", NULL_PARG);
clear_eol();
}
n = 0;
}
#if LOGFILE
/*
* If we have a log file, write the new data to it.
*/
if (!secure && logfile >= 0 && n > 0)
write(logfile, (char *) &bp->data[bp->datasize], n);
#endif
ch_fpos += n;
bp->datasize += n;
if (n == 0)
{
/* Either end of file or no data available.
* read_again indicates the latter. */
if (!read_again)
ch_fsize = pos;
if (ignore_eoi || read_again)
{
/* Wait a while, then try again. */
if (!waiting_for_data)
{
PARG parg;
parg.p_string = wait_message();
ixerror("%s", &parg);
waiting_for_data = TRUE;
}
sleep_ms(50); /* Reduce system load */
}
if (ignore_eoi && follow_mode == FOLLOW_NAME && curr_ifile_changed())
{
/* screen_trashed=2 causes make_display to reopen the file. */
screen_trashed = 2;
return (EOI);
}
if (sigs)
return (EOI);
}
found:
if (ch_bufhead != bn)
{
/*
* Move the buffer to the head of the buffer chain.
* This orders the buffer chain, most- to least-recently used.
*/
BUF_RM(bn);
BUF_INS_HEAD(bn);
/*
* Move to head of hash chain too.
*/
BUF_HASH_RM(bn);
BUF_HASH_INS(bn, h);
}
if (ch_offset < bp->datasize)
break;
/*
* After all that, we still don't have enough data.
* Go back and try again.
*/
}
return (bp->data[ch_offset]);
}
/*
* ch_ungetchar is a rather kludgy and limited way to push
* a single char onto an input file descriptor.
*/
public void ch_ungetchar(int c)
{
if (c != -1 && ch_ungotchar != -1)
error("ch_ungetchar overrun", NULL_PARG);
ch_ungotchar = c;
}
#if LOGFILE
/*
* Close the logfile.
* If we haven't read all of standard input into it, do that now.
*/
public void end_logfile(void)
{
static int tried = FALSE;
if (logfile < 0)
return;
if (!tried && ch_fsize == NULL_POSITION)
{
tried = TRUE;
ierror("Finishing logfile", NULL_PARG);
while (ch_forw_get() != EOI)
if (ABORT_SIGS())
break;
}
close(logfile);
logfile = -1;
free(namelogfile);
namelogfile = NULL;
}
/*
* Start a log file AFTER less has already been running.
* Invoked from the - command; see toggle_option().
* Write all the existing buffered data to the log file.
*/
public void sync_logfile(void)
{
struct buf *bp;
struct bufnode *bn;
int warned = FALSE;
BLOCKNUM block;
BLOCKNUM nblocks;
if (logfile < 0)
return;
nblocks = (ch_fpos + LBUFSIZE - 1) / LBUFSIZE;
for (block = 0; block < nblocks; block++)
{
int wrote = FALSE;
FOR_BUFS(bn)
{
bp = bufnode_buf(bn);
if (bp->block == block)
{
write(logfile, (char *) bp->data, bp->datasize);
wrote = TRUE;
break;
}
}
if (!wrote && !warned)
{
error("Warning: log file is incomplete",
NULL_PARG);
warned = TRUE;
}
}
}
#endif
/*
* Determine if a specific block is currently in one of the buffers.
*/
static int buffered(BLOCKNUM block)
{
struct buf *bp;
struct bufnode *bn;
int h;
h = BUFHASH(block);
FOR_BUFS_IN_CHAIN(h, bn)
{
bp = bufnode_buf(bn);
if (bp->block == block)
return (TRUE);
}
return (FALSE);
}
/*
* Seek to a specified position in the file.
* Return 0 if successful, non-zero if can't seek there.
*/
public int ch_seek(POSITION pos)
{
BLOCKNUM new_block;
POSITION len;
if (thisfile == NULL)
return (0);
len = ch_length();
if (pos < ch_zero() || (len != NULL_POSITION && pos > len))
return (1);
new_block = pos / LBUFSIZE;
if (!(ch_flags & CH_CANSEEK) && pos != ch_fpos && !buffered(new_block))
{
if (ch_fpos > pos)
return (1);
while (ch_fpos < pos)
{
if (ch_forw_get() == EOI)
return (1);
if (ABORT_SIGS())
return (1);
}
return (0);
}
/*
* Set read pointer.
*/
ch_block = new_block;
ch_offset = pos % LBUFSIZE;
return (0);
}
/*
* Seek to the end of the file.
*/
public int ch_end_seek(void)
{
POSITION len;
if (thisfile == NULL)
return (0);
if (ch_flags & CH_CANSEEK)
ch_fsize = filesize(ch_file);
len = ch_length();
if (len != NULL_POSITION)
return (ch_seek(len));
/*
* Do it the slow way: read till end of data.
*/
while (ch_forw_get() != EOI)
if (ABORT_SIGS())
return (1);
return (0);
}
/*
* Seek to the last position in the file that is currently buffered.
*/
public int ch_end_buffer_seek(void)
{
struct buf *bp;
struct bufnode *bn;
POSITION buf_pos;
POSITION end_pos;
if (thisfile == NULL || (ch_flags & CH_CANSEEK))
return (ch_end_seek());
/*
* Seek to the beginning of the file, or as close to it as we can get.
* We may not be able to seek there if input is a pipe and the
* beginning of the pipe is no longer buffered.
*/
public int ch_beg_seek(void)
{
struct bufnode *bn;
struct bufnode *firstbn;
/*
* Try a plain ch_seek first.
*/
if (ch_seek(ch_zero()) == 0)
return (0);
/*
* Can't get to position 0.
* Look thru the buffers for the one closest to position 0.
*/
firstbn = ch_bufhead;
if (firstbn == END_OF_CHAIN)
return (1);
FOR_BUFS(bn)
{
if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
firstbn = bn;
}
ch_block = bufnode_buf(firstbn)->block;
ch_offset = 0;
return (0);
}
/*
* Return the length of the file, if known.
*/
public POSITION ch_length(void)
{
if (thisfile == NULL)
return (NULL_POSITION);
if (ignore_eoi)
return (NULL_POSITION);
if (ch_flags & CH_HELPFILE)
return (size_helpdata);
if (ch_flags & CH_NODATA)
return (0);
return (ch_fsize);
}
/*
* Return the current position in the file.
*/
public POSITION ch_tell(void)
{
if (thisfile == NULL)
return (NULL_POSITION);
return (ch_block * LBUFSIZE) + ch_offset;
}
/*
* Get the current char and post-increment the read pointer.
*/
public int ch_forw_get(void)
{
int c;
if (thisfile == NULL)
return (EOI);
c = ch_get();
if (c == EOI)
return (EOI);
if (ch_offset < LBUFSIZE-1)
ch_offset++;
else
{
ch_block ++;
ch_offset = 0;
}
return (c);
}
/*
* Pre-decrement the read pointer and get the new current char.
*/
public int ch_back_get(void)
{
if (thisfile == NULL)
return (EOI);
if (ch_offset > 0)
ch_offset --;
else
{
if (ch_block <= 0)
return (EOI);
if (!(ch_flags & CH_CANSEEK) && !buffered(ch_block-1))
return (EOI);
ch_block--;
ch_offset = LBUFSIZE-1;
}
return (ch_get());
}
/*
* Set max amount of buffer space.
* bufspace is in units of 1024 bytes. -1 mean no limit.
*/
public void ch_setbufspace(int bufspace)
{
if (bufspace < 0)
maxbufs = -1;
else
{
int lbufk = LBUFSIZE / 1024;
maxbufs = bufspace / lbufk + (bufspace % lbufk != 0);
if (maxbufs < 1)
maxbufs = 1;
}
}
/*
* Flush (discard) any saved file state, including buffer contents.
*/
public void ch_flush(void)
{
struct bufnode *bn;
if (thisfile == NULL)
return;
if (!(ch_flags & CH_CANSEEK))
{
/*
* If input is a pipe, we don't flush buffer contents,
* since the contents can't be recovered.
*/
ch_fsize = NULL_POSITION;
return;
}
/*
* Initialize all the buffers.
*/
FOR_BUFS(bn)
{
bufnode_buf(bn)->block = -1;
}
/*
* Figure out the size of the file, if we can.
*/
ch_fsize = filesize(ch_file);
/*
* Seek to a known position: the beginning of the file.
*/
ch_fpos = 0;
ch_block = 0; /* ch_fpos / LBUFSIZE; */
ch_offset = 0; /* ch_fpos % LBUFSIZE; */
#if HAVE_PROCFS
/*
* This is a kludge to workaround a Linux kernel bug: files in
* /proc have a size of 0 according to fstat() but have readable
* data. They are sometimes, but not always, seekable.
* Force them to be non-seekable here.
*/
if (ch_fsize == 0)
{
struct statfs st;
if (fstatfs(ch_file, &st) == 0)
{
if (st.f_type == PROC_SUPER_MAGIC)
{
ch_fsize = NULL_POSITION;
ch_flags &= ~CH_CANSEEK;
}
}
}
#endif
if (lseek(ch_file, (off_t)0, SEEK_SET) == BAD_LSEEK)
{
/*
* Warning only; even if the seek fails for some reason,
* there's a good chance we're at the beginning anyway.
* {{ I think this is bogus reasoning. }}
*/
error("seek error to 0", NULL_PARG);
}
}
/*
* Allocate a new buffer.
* The buffer is added to the tail of the buffer chain.
*/
static int ch_addbuf(void)
{
struct buf *bp;
struct bufnode *bn;
/*
* Allocate and initialize a new buffer and link it
* onto the tail of the buffer list.
*/
bp = (struct buf *) calloc(1, sizeof(struct buf));
if (bp == NULL)
return (1);
ch_nbufs++;
bp->block = -1;
bn = &bp->node;
/*
* Is it possible to seek on a file descriptor?
*/
public int seekable(int f)
{
#if MSDOS_COMPILER
extern int fd0;
if (f == fd0 && !isatty(fd0))
{
/*
* In MS-DOS, pipes are seekable. Check for
* standard input, and pretend it is not seekable.
*/
return (0);
}
#endif
return (lseek(f, (off_t)1, SEEK_SET) != BAD_LSEEK);
}
/*
* Force EOF to be at the current read position.
* This is used after an ignore_eof read, during which the EOF may change.
*/
public void ch_set_eof(void)
{
if (ch_fsize != NULL_POSITION && ch_fsize < ch_fpos)
ch_fsize = ch_fpos;
}
/*
* Initialize file state for a new file.
*/
public void ch_init(int f, int flags)
{
/*
* See if we already have a filestate for this file.
*/
thisfile = (struct filestate *) get_filestate(curr_ifile);
if (thisfile == NULL)
{
/*
* Allocate and initialize a new filestate.
*/
thisfile = (struct filestate *)
ecalloc(1, sizeof(struct filestate));
thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
thisfile->nbufs = 0;
thisfile->flags = flags;
thisfile->fpos = 0;
thisfile->block = 0;
thisfile->offset = 0;
thisfile->file = -1;
thisfile->fsize = NULL_POSITION;
init_hashtbl();
/*
* Try to seek; set CH_CANSEEK if it works.
*/
if ((flags & CH_CANSEEK) && !seekable(f))
ch_flags &= ~CH_CANSEEK;
set_filestate(curr_ifile, (void *) thisfile);
}
if (thisfile->file == -1)
thisfile->file = f;
ch_flush();
}
/*
* Close a filestate.
*/
public void ch_close(void)
{
int keepstate = FALSE;
if (thisfile == NULL)
return;
if ((ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE)) && !(ch_flags & CH_KEEPOPEN))
{
/*
* We can seek or re-open, so we don't need to keep buffers.
*/
ch_delbufs();
} else
keepstate = TRUE;
if (!(ch_flags & CH_KEEPOPEN))
{
/*
* We don't need to keep the file descriptor open
* (because we can re-open it.)
* But don't really close it if it was opened via popen(),
* because pclose() wants to close it.
*/
if (!(ch_flags & (CH_POPENED|CH_HELPFILE)))
close(ch_file);
ch_file = -1;
} else
keepstate = TRUE;
if (!keepstate)
{
/*
* We don't even need to keep the filestate structure.
*/
free(thisfile);
thisfile = NULL;
set_filestate(curr_ifile, (void *) NULL);
}
}
/*
* Return ch_flags for the current file.
*/
public int ch_getflags(void)
{
if (thisfile == NULL)
return (0);
return (ch_flags);
}
