/* $NetBSD: ch.c,v 1.6 2003/10/13 14:34:25 agc Exp $ */
/*
* Copyright (c) 1988 Mark Nudelman
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)ch.c 8.1 (Berkeley) 6/6/93";
#else
__RCSID("$NetBSD: ch.c,v 1.6 2003/10/13 14:34:25 agc Exp $");
#endif
#endif /* not lint */
/*
* 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.
*/
#include <sys/types.h>
#include <sys/file.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <err.h>
#include "less.h"
#include "extern.h"
int file = -1; /* File descriptor of the input file */
/*
* Pool of buffers holding the most recently used blocks of the input file.
*/
struct buf {
struct buf *next, *prev;
long block;
int datasize;
char data[BUFSIZ];
};
int nbufs;
/*
* 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 buf_anchor.
*/
#define END_OF_CHAIN ((struct buf *)&buf_anchor)
#define buf_head buf_anchor.next
#define buf_tail buf_anchor.prev
static struct {
struct buf *next, *prev;
} buf_anchor = { END_OF_CHAIN, END_OF_CHAIN };
/*
* Current position in file.
* Stored as a block number and an offset into the block.
*/
static long ch_block;
static int ch_offset;
/* Length of file, needed if input is a pipe. */
static off_t ch_fsize;
/* Number of bytes read, if input is standard input (a pipe). */
static off_t last_piped_pos;
/*
* Get the character pointed to by the read pointer. ch_get() is a macro
* which is more efficient to call than fch_get (the function), in the usual
* case that the block desired is at the head of the chain.
*/
#define ch_get() \
((buf_head->block == ch_block && \
ch_offset < buf_head->datasize) ? \
buf_head->data[ch_offset] : fch_get())
static int fch_get __P((void));
static int buffered __P((long));
static int
fch_get()
{
struct buf *bp;
int n, ch;
char *p, *t;
off_t pos;
/* look for a buffer holding the desired block. */
for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
if (bp->block == ch_block) {
if (ch_offset >= bp->datasize)
/*
* Need more data in this buffer.
*/
goto read_more;
/*
* On a pipe, we don't sort the buffers LRU
* because this can cause gaps in the buffers.
* For example, suppose we've got 12 1K buffers,
* and a 15K input stream. If we read the first 12K
* sequentially, then jump to line 1, then jump to
* the end, the buffers have blocks 0,4,5,6,..,14.
* If we then jump to line 1 again and try to
* read sequentially, we're out of luck when we
* get to block 1 (we'd get the "pipe error" below).
* To avoid this, we only sort buffers on a pipe
* when we actually READ the data, not when we
* find it already buffered.
*/
if (ispipe)
return(bp->data[ch_offset]);
goto found;
}
/*
* 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, and input is a pipe, then try to allocate a new buffer first.
*/
if (ispipe && buf_tail->block != (long)(-1))
(void)ch_addbuf(1);
bp = buf_tail;
bp->block = ch_block;
bp->datasize = 0;
read_more:
pos = (ch_block * BUFSIZ) + bp->datasize;
if (ispipe) {
/*
* The data requested should be immediately after
* the last data read from the pipe.
*/
if (pos != last_piped_pos) {
error("pipe error");
quit();
}
} else
(void)lseek(file, pos, L_SET);
/*
* Read the block.
* If we read less than a full block, we just return the
* partial block and pick up the rest next time.
*/
n = iread(file, &bp->data[bp->datasize], BUFSIZ - bp->datasize);
if (n == READ_INTR)
return (EOI);
if (n < 0) {
error("read error");
quit();
}
if (ispipe)
last_piped_pos += n;
p = &bp->data[bp->datasize];
bp->datasize += n;
/*
* Set an EOI marker in the buffered data itself. Then ensure the
* data is "clean": there are no extra EOI chars in the data and
* that the "meta" bit (the 0200 bit) is reset in each char;
* also translate \r\n sequences to \n if -u flag not set.
*/
if (n == 0) {
ch_fsize = pos;
bp->data[bp->datasize++] = EOI;
}
if (bs_mode) {
for (p = &bp->data[bp->datasize]; --n >= 0;) {
*--p &= 0177;
if (*p == EOI)
*p = 0200;
}
}
else {
for (t = p; --n >= 0; ++p) {
ch = *p & 0177;
if (ch == '\r' && n && (p[1] & 0177) == '\n') {
++p;
*t++ = '\n';
}
else
*t++ = (ch == EOI) ? 0200 : ch;
}
if (p != t) {
bp->datasize -= p - t;
if (ispipe)
last_piped_pos -= p - t;
}
}
found:
if (buf_head != bp) {
/*
* Move the buffer to the head of the buffer chain.
* This orders the buffer chain, most- to least-recently used.
*/
bp->next->prev = bp->prev;
bp->prev->next = bp->next;
bp->next = buf_head;
bp->prev = END_OF_CHAIN;
buf_head->prev = bp;
buf_head = bp;
}
if (ch_offset >= bp->datasize)
/*
* After all that, we still don't have enough data.
* Go back and try again.
*/
goto read_more;
return(bp->data[ch_offset]);
}
/*
* Determine if a specific block is currently in one of the buffers.
*/
static int
buffered(block)
long block;
{
struct buf *bp;
for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
if (bp->block == block)
return(1);
return(0);
}
/*
* Seek to a specified position in the file.
* Return 0 if successful, non-zero if can't seek there.
*/
int
ch_seek(pos)
off_t pos;
{
long new_block;
new_block = pos / BUFSIZ;
if (!ispipe || pos == last_piped_pos || buffered(new_block)) {
/*
* Set read pointer.
*/
ch_block = new_block;
ch_offset = pos % BUFSIZ;
return(0);
}
return(1);
}
/*
* Seek to the end of the file.
*/
int
ch_end_seek()
{
if (!ispipe)
return(ch_seek(ch_length()));
/*
* Do it the slow way: read till end of data.
*/
while (ch_forw_get() != EOI)
if (sigs)
return(1);
return(0);
}
/*
* 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.
*/
int
ch_beg_seek()
{
struct buf *bp, *firstbp;
/*
* Try a plain ch_seek first.
*/
if (ch_seek((off_t)0) == 0)
return(0);
/*
* Can't get to position 0.
* Look thru the buffers for the one closest to position 0.
*/
firstbp = bp = buf_head;
if (bp == END_OF_CHAIN)
return(1);
while ((bp = bp->next) != END_OF_CHAIN)
if (bp->block < firstbp->block)
firstbp = bp;
ch_block = firstbp->block;
ch_offset = 0;
return(0);
}
/*
* Return the length of the file, if known.
*/
off_t
ch_length()
{
if (ispipe)
return(ch_fsize);
return((off_t)(lseek(file, (off_t)0, L_XTND)));
}
/*
* Return the current position in the file.
*/
off_t
ch_tell()
{
return(ch_block * BUFSIZ + ch_offset);
}
/*
* Get the current char and post-increment the read pointer.
*/
int
ch_forw_get()
{
int c;
c = ch_get();
if (c != EOI && ++ch_offset >= BUFSIZ) {
ch_offset = 0;
++ch_block;
}
return(c);
}
/*
* Pre-decrement the read pointer and get the new current char.
*/
int
ch_back_get()
{
if (--ch_offset < 0) {
if (ch_block <= 0 || (ispipe && !buffered(ch_block-1))) {
ch_offset = 0;
return(EOI);
}
ch_offset = BUFSIZ - 1;
ch_block--;
}
return(ch_get());
}
/*
* Allocate buffers.
* Caller wants us to have a total of at least want_nbufs buffers.
* keep==1 means keep the data in the current buffers;
* otherwise discard the old data.
*/
void
ch_init(want_nbufs, keep)
int want_nbufs;
int keep;
{
struct buf *bp;
char message[80];
cbufs = nbufs;
if (nbufs < want_nbufs && ch_addbuf(want_nbufs - nbufs)) {
/*
* Cannot allocate enough buffers.
* If we don't have ANY, then quit.
* Otherwise, just report the error and return.
*/
(void)snprintf(message, sizeof(message),
"cannot allocate %d buffers", want_nbufs - nbufs);
error(message);
if (nbufs == 0)
quit();
return;
}
if (keep)
return;
/*
* We don't want to keep the old data,
* so initialize all the buffers now.
*/
for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
bp->block = (long)(-1);
last_piped_pos = (off_t)0;
ch_fsize = NULL_POSITION;
(void)ch_seek((off_t)0);
}
/*
* Allocate some new buffers.
* The buffers are added to the tail of the buffer chain.
*/
int
ch_addbuf(nnew)
int nnew;
{
struct buf *bp;
struct buf *newbufs;
/*
* We don't have enough buffers.
* Allocate some new ones.
*/
newbufs = (struct buf *)calloc((u_int)nnew, sizeof(struct buf));
if (newbufs == NULL)
return(1);
/*
* Initialize the new buffers and link them together.
* Link them all onto the tail of the buffer list.
*/
nbufs += nnew;
cbufs = nbufs;
for (bp = &newbufs[0]; bp < &newbufs[nnew]; bp++) {
bp->next = bp + 1;
bp->prev = bp - 1;
bp->block = (long)(-1);
}
newbufs[nnew-1].next = END_OF_CHAIN;
newbufs[0].prev = buf_tail;
buf_tail->next = &newbufs[0];
buf_tail = &newbufs[nnew-1];
return(0);
}