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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.
* 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[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
#endif /* not lint */
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "extern.h"
static void rlines __P((FILE *, long, struct stat *));
/*
* forward -- display the file, from an offset, forward.
*
* There are eight separate cases for this -- regular and non-regular
* files, by bytes or lines and from the beginning or end of the file.
*
* FBYTES byte offset from the beginning of the file
* REG seek
* NOREG read, counting bytes
*
* FLINES line offset from the beginning of the file
* REG read, counting lines
* NOREG read, counting lines
*
* RBYTES byte offset from the end of the file
* REG seek
* NOREG cyclically read characters into a wrap-around buffer
*
* RLINES
* REG mmap the file and step back until reach the correct offset.
* NOREG cyclically read lines into a wrap-around array of buffers
*/
void
forward(fp, style, off, sbp)
FILE *fp;
enum STYLE style;
long off;
struct stat *sbp;
{
register int ch;
struct timeval second;
fd_set zero;
switch(style) {
case FBYTES:
if (off == 0)
break;
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size < off)
off = sbp->st_size;
if (fseek(fp, off, SEEK_SET) == -1) {
ierr();
return;
}
} else while (off--)
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr();
return;
}
break;
}
break;
case FLINES:
if (off == 0)
break;
for (;;) {
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr();
return;
}
break;
}
if (ch == '\n' && !--off)
break;
}
break;
case RBYTES:
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size >= off &&
fseek(fp, -off, SEEK_END) == -1) {
ierr();
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
bytes(fp, off);
break;
case RLINES:
if (S_ISREG(sbp->st_mode))
if (!off) {
if (fseek(fp, 0L, SEEK_END) == -1) {
ierr();
return;
}
} else
rlines(fp, off, sbp);
else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
lines(fp, off);
break;
}
/*
* We pause for one second after displaying any data that has
* accumulated since we read the file.
*/
if (fflag) {
FD_ZERO(&zero);
second.tv_sec = 1;
second.tv_usec = 0;
}
for (;;) {
while ((ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr();
return;
}
(void)fflush(stdout);
if (!fflag)
break;
/* Sleep(3) is eight system calls. Do it fast. */
if (select(0, &zero, &zero, &zero, &second) == -1)
err(1, "select: %s", strerror(errno));
clearerr(fp);
}
}
/*
* rlines -- display the last offset lines of the file.
*/
static void
rlines(fp, off, sbp)
FILE *fp;
long off;
struct stat *sbp;
{
register off_t size;
register char *p;
char *start;
if (!(size = sbp->st_size))
return;
if (size > SIZE_T_MAX) {
err(0, "%s: %s", fname, strerror(EFBIG));
return;
}
if ((start = mmap(NULL, (size_t)size,
PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) {
err(0, "%s: %s", fname, strerror(EFBIG));
return;
}
/* Last char is special, ignore whether newline or not. */
for (p = start + size - 1; --size;)
if (*--p == '\n' && !--off) {
++p;
break;
}
/* Set the file pointer to reflect the length displayed. */
size = sbp->st_size - size;
WR(p, size);
if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) {
ierr();
return;
}
if (munmap(start, (size_t)sbp->st_size)) {
err(0, "%s: %s", fname, strerror(errno));
return;
}
}
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