454 lines
11 KiB
C
454 lines
11 KiB
C
/*
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* Copyright (c) 1988 Mark Nudleman
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* Copyright (c) 1988 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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/* from: static char sccsid[] = "@(#)ch.c 5.11 (Berkeley) 6/21/92"; */
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static char *rcsid = "$Id: ch.c,v 1.3 1994/04/06 17:50:39 cgd Exp $";
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#endif /* not lint */
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/*
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* Low level character input from the input file.
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* We use these special purpose routines which optimize moving
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* both forward and backward from the current read pointer.
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*/
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#include <sys/types.h>
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#include <sys/file.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <less.h>
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int file = -1; /* File descriptor of the input file */
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/*
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* Pool of buffers holding the most recently used blocks of the input file.
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*/
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struct buf {
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struct buf *next, *prev;
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long block;
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int datasize;
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char data[BUFSIZ];
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};
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int nbufs;
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/*
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* The buffer pool is kept as a doubly-linked circular list, in order from
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* most- to least-recently used. The circular list is anchored by buf_anchor.
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*/
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#define END_OF_CHAIN ((struct buf *)&buf_anchor)
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#define buf_head buf_anchor.next
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#define buf_tail buf_anchor.prev
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static struct {
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struct buf *next, *prev;
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} buf_anchor = { END_OF_CHAIN, END_OF_CHAIN };
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extern int ispipe, cbufs, sigs;
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/*
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* Current position in file.
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* Stored as a block number and an offset into the block.
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*/
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static long ch_block;
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static int ch_offset;
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/* Length of file, needed if input is a pipe. */
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static off_t ch_fsize;
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/* Number of bytes read, if input is standard input (a pipe). */
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static off_t last_piped_pos;
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/*
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* Get the character pointed to by the read pointer. ch_get() is a macro
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* which is more efficient to call than fch_get (the function), in the usual
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* case that the block desired is at the head of the chain.
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*/
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#define ch_get() \
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((buf_head->block == ch_block && \
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ch_offset < buf_head->datasize) ? \
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buf_head->data[ch_offset] : fch_get())
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static
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fch_get()
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{
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extern int bs_mode;
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register struct buf *bp;
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register int n, ch;
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register char *p, *t;
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off_t pos;
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/* look for a buffer holding the desired block. */
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for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
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if (bp->block == ch_block) {
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if (ch_offset >= bp->datasize)
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/*
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* Need more data in this buffer.
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*/
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goto read_more;
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/*
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* On a pipe, we don't sort the buffers LRU
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* because this can cause gaps in the buffers.
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* For example, suppose we've got 12 1K buffers,
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* and a 15K input stream. If we read the first 12K
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* sequentially, then jump to line 1, then jump to
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* the end, the buffers have blocks 0,4,5,6,..,14.
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* If we then jump to line 1 again and try to
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* read sequentially, we're out of luck when we
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* get to block 1 (we'd get the "pipe error" below).
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* To avoid this, we only sort buffers on a pipe
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* when we actually READ the data, not when we
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* find it already buffered.
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*/
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if (ispipe)
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return(bp->data[ch_offset]);
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goto found;
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}
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/*
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* Block is not in a buffer. Take the least recently used buffer
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* and read the desired block into it. If the LRU buffer has data
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* in it, and input is a pipe, then try to allocate a new buffer first.
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*/
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if (ispipe && buf_tail->block != (long)(-1))
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(void)ch_addbuf(1);
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bp = buf_tail;
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bp->block = ch_block;
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bp->datasize = 0;
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read_more:
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pos = (ch_block * BUFSIZ) + bp->datasize;
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if (ispipe) {
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/*
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* The data requested should be immediately after
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* the last data read from the pipe.
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*/
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if (pos != last_piped_pos) {
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error("pipe error");
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quit();
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}
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} else
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(void)lseek(file, pos, L_SET);
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/*
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* Read the block.
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* If we read less than a full block, we just return the
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* partial block and pick up the rest next time.
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*/
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n = iread(file, &bp->data[bp->datasize], BUFSIZ - bp->datasize);
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if (n == READ_INTR)
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return (EOI);
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if (n < 0) {
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error("read error");
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quit();
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}
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if (ispipe)
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last_piped_pos += n;
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p = &bp->data[bp->datasize];
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bp->datasize += n;
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/*
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* Set an EOI marker in the buffered data itself. Then ensure the
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* data is "clean": there are no extra EOI chars in the data and
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* that the "meta" bit (the 0200 bit) is reset in each char;
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* also translate \r\n sequences to \n if -u flag not set.
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*/
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if (n == 0) {
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ch_fsize = pos;
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bp->data[bp->datasize++] = EOI;
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}
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if (bs_mode) {
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for (p = &bp->data[bp->datasize]; --n >= 0;) {
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*--p &= 0177;
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if (*p == EOI)
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*p = 0200;
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}
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}
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else {
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for (t = p; --n >= 0; ++p) {
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ch = *p & 0177;
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if (ch == '\r' && n && (p[1] & 0177) == '\n') {
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++p;
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*t++ = '\n';
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}
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else
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*t++ = (ch == EOI) ? 0200 : ch;
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}
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if (p != t) {
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bp->datasize -= p - t;
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if (ispipe)
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last_piped_pos -= p - t;
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}
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}
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found:
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if (buf_head != bp) {
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/*
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* Move the buffer to the head of the buffer chain.
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* This orders the buffer chain, most- to least-recently used.
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*/
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bp->next->prev = bp->prev;
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bp->prev->next = bp->next;
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bp->next = buf_head;
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bp->prev = END_OF_CHAIN;
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buf_head->prev = bp;
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buf_head = bp;
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}
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if (ch_offset >= bp->datasize)
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/*
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* After all that, we still don't have enough data.
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* Go back and try again.
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*/
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goto read_more;
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return(bp->data[ch_offset]);
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}
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/*
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* Determine if a specific block is currently in one of the buffers.
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*/
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static
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buffered(block)
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long block;
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{
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register struct buf *bp;
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for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
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if (bp->block == block)
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return(1);
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return(0);
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}
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/*
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* Seek to a specified position in the file.
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* Return 0 if successful, non-zero if can't seek there.
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*/
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ch_seek(pos)
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register off_t pos;
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{
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long new_block;
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new_block = pos / BUFSIZ;
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if (!ispipe || pos == last_piped_pos || buffered(new_block)) {
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/*
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* Set read pointer.
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*/
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ch_block = new_block;
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ch_offset = pos % BUFSIZ;
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return(0);
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}
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return(1);
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}
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/*
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* Seek to the end of the file.
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*/
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ch_end_seek()
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{
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off_t ch_length();
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if (!ispipe)
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return(ch_seek(ch_length()));
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/*
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* Do it the slow way: read till end of data.
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*/
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while (ch_forw_get() != EOI)
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if (sigs)
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return(1);
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return(0);
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}
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/*
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* Seek to the beginning of the file, or as close to it as we can get.
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* We may not be able to seek there if input is a pipe and the
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* beginning of the pipe is no longer buffered.
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*/
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ch_beg_seek()
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{
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register struct buf *bp, *firstbp;
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/*
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* Try a plain ch_seek first.
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*/
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if (ch_seek((off_t)0) == 0)
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return(0);
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/*
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* Can't get to position 0.
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* Look thru the buffers for the one closest to position 0.
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*/
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firstbp = bp = buf_head;
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if (bp == END_OF_CHAIN)
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return(1);
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while ((bp = bp->next) != END_OF_CHAIN)
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if (bp->block < firstbp->block)
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firstbp = bp;
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ch_block = firstbp->block;
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ch_offset = 0;
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return(0);
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}
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/*
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* Return the length of the file, if known.
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*/
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off_t
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ch_length()
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{
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if (ispipe)
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return(ch_fsize);
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return((off_t)(lseek(file, (off_t)0, L_XTND)));
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}
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/*
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* Return the current position in the file.
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*/
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off_t
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ch_tell()
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{
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return(ch_block * BUFSIZ + ch_offset);
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}
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/*
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* Get the current char and post-increment the read pointer.
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*/
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ch_forw_get()
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{
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register int c;
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c = ch_get();
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if (c != EOI && ++ch_offset >= BUFSIZ) {
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ch_offset = 0;
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++ch_block;
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}
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return(c);
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}
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/*
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* Pre-decrement the read pointer and get the new current char.
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*/
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ch_back_get()
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{
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if (--ch_offset < 0) {
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if (ch_block <= 0 || (ispipe && !buffered(ch_block-1))) {
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ch_offset = 0;
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return(EOI);
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}
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ch_offset = BUFSIZ - 1;
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ch_block--;
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}
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return(ch_get());
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}
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/*
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* Allocate buffers.
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* Caller wants us to have a total of at least want_nbufs buffers.
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* keep==1 means keep the data in the current buffers;
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* otherwise discard the old data.
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*/
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ch_init(want_nbufs, keep)
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int want_nbufs;
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int keep;
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{
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register struct buf *bp;
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char message[80];
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cbufs = nbufs;
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if (nbufs < want_nbufs && ch_addbuf(want_nbufs - nbufs)) {
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/*
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* Cannot allocate enough buffers.
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* If we don't have ANY, then quit.
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* Otherwise, just report the error and return.
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*/
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(void)sprintf(message, "cannot allocate %d buffers",
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want_nbufs - nbufs);
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error(message);
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if (nbufs == 0)
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quit();
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return;
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}
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if (keep)
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return;
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/*
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* We don't want to keep the old data,
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* so initialize all the buffers now.
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*/
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for (bp = buf_head; bp != END_OF_CHAIN; bp = bp->next)
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bp->block = (long)(-1);
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last_piped_pos = (off_t)0;
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ch_fsize = NULL_POSITION;
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(void)ch_seek((off_t)0);
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}
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/*
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* Allocate some new buffers.
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* The buffers are added to the tail of the buffer chain.
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*/
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ch_addbuf(nnew)
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int nnew;
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{
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register struct buf *bp;
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register struct buf *newbufs;
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char *calloc();
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/*
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* We don't have enough buffers.
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* Allocate some new ones.
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*/
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newbufs = (struct buf *)calloc((u_int)nnew, sizeof(struct buf));
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if (newbufs == NULL)
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return(1);
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/*
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* Initialize the new buffers and link them together.
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* Link them all onto the tail of the buffer list.
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*/
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nbufs += nnew;
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cbufs = nbufs;
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for (bp = &newbufs[0]; bp < &newbufs[nnew]; bp++) {
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bp->next = bp + 1;
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bp->prev = bp - 1;
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bp->block = (long)(-1);
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}
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newbufs[nnew-1].next = END_OF_CHAIN;
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newbufs[0].prev = buf_tail;
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buf_tail->next = &newbufs[0];
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buf_tail = &newbufs[nnew-1];
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return(0);
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}
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