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+/*
+ * Copyright (c) 1988 Mark Nudleman
+ * 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. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. 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.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)ch.c 8.1 (Berkeley) 6/6/93";
+#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 <stdio.h>
+#include <less.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 };
+
+extern int ispipe, cbufs, sigs;
+
+/*
+ * 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
+fch_get()
+{
+ extern int bs_mode;
+ register struct buf *bp;
+ register int n, ch;
+ register char *p, *t;
+ off_t pos, lseek();
+
+ /* 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
+buffered(block)
+ long block;
+{
+ register 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.
+ */
+ch_seek(pos)
+ register 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.
+ */
+ch_end_seek()
+{
+ off_t ch_length();
+
+ 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.
+ */
+ch_beg_seek()
+{
+ register 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()
+{
+ off_t lseek();
+
+ 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.
+ */
+ch_forw_get()
+{
+ register 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.
+ */
+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.
+ */
+ch_init(want_nbufs, keep)
+ int want_nbufs;
+ int keep;
+{
+ register 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)sprintf(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.
+ */
+ch_addbuf(nnew)
+ int nnew;
+{
+ register struct buf *bp;
+ register struct buf *newbufs;
+ char *calloc();
+
+ /*
+ * 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);
+}
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