freebsd-skq/usr.bin/tail/reverse.c

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/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Edward Sze-Tyan Wang.
*
* 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.
* 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.
*/
#if 0
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#ifndef lint
static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93";
#endif /* not lint */
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#endif
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#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
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#include <sys/param.h>
#include <sys/stat.h>
#include <sys/mman.h>
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#include <err.h>
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#include <errno.h>
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#include <limits.h>
#include <stdint.h>
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
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#include <unistd.h>
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#include "extern.h"
static void r_buf(FILE *, const char *);
static void r_reg(FILE *, const char *, enum STYLE, off_t, struct stat *);
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/*
* reverse -- display input in reverse order by line.
*
* There are six separate cases for this -- regular and non-regular
* files by bytes, lines or the whole file.
*
* BYTES display N bytes
* REG mmap the file and display the lines
* NOREG cyclically read characters into a wrap-around buffer
*
* LINES display N lines
* REG mmap the file and display the lines
* NOREG cyclically read lines into a wrap-around array of buffers
*
* FILE display the entire file
* REG mmap the file and display the lines
* NOREG cyclically read input into a linked list of buffers
*/
void
reverse(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
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{
if (style != REVERSE && off == 0)
return;
if (S_ISREG(sbp->st_mode))
r_reg(fp, fn, style, off, sbp);
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else
switch(style) {
case FBYTES:
case RBYTES:
bytes(fp, fn, off);
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break;
case FLINES:
case RLINES:
lines(fp, fn, off);
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break;
case REVERSE:
r_buf(fp, fn);
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break;
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default:
break;
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}
}
/*
* r_reg -- display a regular file in reverse order by line.
*/
static void
r_reg(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
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{
struct mapinfo map;
off_t curoff, size, lineend;
int i;
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if (!(size = sbp->st_size))
return;
map.start = NULL;
map.mapoff = map.maxoff = size;
map.fd = fileno(fp);
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/*
* Last char is special, ignore whether newline or not. Note that
* size == 0 is dealt with above, and size == 1 sets curoff to -1.
*/
curoff = size - 2;
lineend = size;
while (curoff >= 0) {
if (curoff < map.mapoff ||
curoff >= map.mapoff + (off_t)map.maplen) {
if (maparound(&map, curoff) != 0) {
ierr(fn);
return;
}
}
for (i = curoff - map.mapoff; i >= 0; i--) {
if (style == RBYTES && --off == 0)
break;
if (map.start[i] == '\n')
break;
}
/* `i' is either the map offset of a '\n', or -1. */
curoff = map.mapoff + i;
if (i < 0)
continue;
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/* Print the line and update offsets. */
if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
ierr(fn);
return;
}
lineend = curoff + 1;
curoff--;
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if (style == RLINES)
off--;
if (off == 0 && style != REVERSE) {
/* Avoid printing anything below. */
curoff = 0;
break;
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}
}
if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
ierr(fn);
return;
}
if (map.start != NULL && munmap(map.start, map.maplen))
ierr(fn);
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}
typedef struct bf {
struct bf *next;
struct bf *prev;
int len;
char *l;
} BF;
/*
* r_buf -- display a non-regular file in reverse order by line.
*
* This is the function that saves the entire input, storing the data in a
* doubly linked list of buffers and then displays them in reverse order.
* It has the usual nastiness of trying to find the newlines, as there's no
* guarantee that a newline occurs anywhere in the file, let alone in any
* particular buffer. If we run out of memory, input is discarded (and the
* user warned).
*/
static void
r_buf(FILE *fp, const char *fn)
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{
BF *mark, *tl, *tr;
int ch, len, llen;
char *p;
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off_t enomem;
tl = NULL;
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#define BSZ (128 * 1024)
for (mark = NULL, enomem = 0;;) {
/*
* Allocate a new block and link it into place in a doubly
* linked list. If out of memory, toss the LRU block and
* keep going.
*/
if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
(tl->l = malloc(BSZ)) == NULL) {
if (!mark)
err(1, "malloc");
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tl = enomem ? tl->next : mark;
enomem += tl->len;
} else if (mark) {
tl->next = mark;
tl->prev = mark->prev;
mark->prev->next = tl;
mark->prev = tl;
} else {
mark = tl;
mark->next = mark->prev = mark;
}
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/* Fill the block with input data. */
for (p = tl->l, len = 0;
len < BSZ && (ch = getc(fp)) != EOF; ++len)
*p++ = ch;
if (ferror(fp)) {
ierr(fn);
return;
}
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/*
* If no input data for this block and we tossed some data,
* recover it.
*/
if (!len && enomem) {
enomem -= tl->len;
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tl = tl->prev;
break;
}
tl->len = len;
if (ch == EOF)
break;
}
if (enomem) {
warnx("warning: %jd bytes discarded", (intmax_t)enomem);
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rval = 1;
}
/*
* Step through the blocks in the reverse order read. The last char
* is special, ignore whether newline or not.
*/
for (mark = tl;;) {
for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
--p, ++llen)
if (*p == '\n') {
if (llen) {
WR(p + 1, llen);
llen = 0;
}
if (tl == mark)
continue;
for (tr = tl->next; tr->len; tr = tr->next) {
WR(tr->l, tr->len);
tr->len = 0;
if (tr == mark)
break;
}
}
tl->len = llen;
if ((tl = tl->prev) == mark)
break;
}
tl = tl->next;
if (tl->len) {
WR(tl->l, tl->len);
tl->len = 0;
}
while ((tl = tl->next)->len) {
WR(tl->l, tl->len);
tl->len = 0;
}
}