OpenBSD-4.6/usr.bin/tail/reverse.c
/* $OpenBSD: reverse.c,v 1.18 2007/09/29 12:31:28 otto Exp $ */
/* $NetBSD: reverse.c,v 1.6 1994/11/23 07:42:10 jtc Exp $ */
/*-
* 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.
* 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.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93";
#endif
static char rcsid[] = "$OpenBSD: reverse.c,v 1.18 2007/09/29 12:31:28 otto Exp $";
#endif /* not lint */
#include <sys/stat.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "extern.h"
static void r_buf(FILE *);
static int r_reg(FILE *, enum STYLE, off_t, struct stat *);
#define COPYCHAR(fp, ch) \
do { \
if ((ch = getc(fp)) == EOF) { \
ierr(); \
return (0); \
} \
if (putchar(ch) == EOF) { \
oerr(); \
return (0); \
} \
} while (0)
/*
* 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 reverse scan and display the lines
* NOREG cyclically read characters into a wrap-around buffer
*
* LINES display N lines
* REG reverse scan and display the lines
* NOREG cyclically read lines into a wrap-around array of buffers
*
* FILE display the entire file
* REG reverse scan and display the lines
* NOREG cyclically read input into a linked list of buffers
*/
void
reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
{
if (style != REVERSE && off == 0)
return;
if (!S_ISREG(sbp->st_mode) || r_reg(fp, style, off, sbp) != 0)
switch(style) {
case FBYTES:
case RBYTES:
(void)bytes(fp, off);
break;
case FLINES:
case RLINES:
(void)lines(fp, off);
break;
case REVERSE:
r_buf(fp);
break;
}
}
/*
* r_reg -- display a regular file in reverse order by line.
*/
static int
r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
{
off_t start, pos, end;
int ch;
end = sbp->st_size;
if (end == 0)
return (0);
/* Position before char, ignore last char whether newline or not */
pos = end-2;
ch = EOF;
start = 0;
if (style == RBYTES && off < end)
start = end - off;
for (; pos >= start; pos--) {
/* A seek per char isn't a problem with a smart stdio */
if (fseeko(fp, pos, SEEK_SET) != 0) {
ierr();
return (0);
}
if ((ch = getc(fp)) == '\n') {
while (--end > pos)
COPYCHAR(fp, ch);
end++;
if (style == RLINES && --off == 0)
break;
}
else if (ch == EOF) {
ierr();
return (0);
}
}
if (pos < start) {
if (ch != EOF && ungetc(ch, fp) == EOF) {
ierr();
return (0);
}
while (--end >= start)
COPYCHAR(fp, ch);
}
return (0);
}
typedef struct bf {
struct bf *next;
struct bf *prev;
size_t 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)
{
BF *mark, *tr, *tl = NULL;
int ch;
size_t len, llen;
char *p;
off_t enomem;
#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, NULL);
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;
}
if (!enomem)
tl->len = 0;
/* Fill the block with input data. */
for (p = tl->l, len = 0;
len < BSZ && (ch = getc(fp)) != EOF; ++len)
*p++ = ch;
/*
* If no input data for this block and we tossed some data,
* recover it.
*/
if (!len) {
if (enomem)
enomem -= tl->len;
tl = tl->prev;
break;
}
tl->len = len;
if (ch == EOF)
break;
}
if (enomem) {
(void)fprintf(stderr,
"tail: warning: %lld bytes discarded\n", (long long)enomem);
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;
}
}