/*
* 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(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
{
int ch;
switch(style) {
case FBYTES:
if (off == 0)
break;
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size < off)
off = sbp->st_size;
if (fseeko(fp, off, SEEK_SET) == -1) {
ierr(fn);
return;
}
} else while (off--)
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr(fn);
return;
}
break;
}
break;
case FLINES:
if (off == 0)
break;
for (;;) {
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr(fn);
return;
}
break;
}
if (ch == '\n' && !--off)
break;
}
break;
case RBYTES:
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size >= off &&
fseeko(fp, -off, SEEK_END) == -1) {
ierr(fn);
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr(fn);
return;
}
} else
if (bytes(fp, fn, off))
return;
break;
case RLINES:
if (S_ISREG(sbp->st_mode))
if (!off) {
if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
ierr(fn);
return;
}
} else
rlines(fp, fn, off, sbp);
else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr(fn);
return;
}
} else
if (lines(fp, fn, off))
return;
break;
default:
break;
}
while ((ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr(fn);
return;
}
(void)fflush(stdout);
}
/*
* 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(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
{
int ch, n;
int kq=-1, action=USE_SLEEP;
struct stat statbuf;
struct kevent ev[2];
switch(style) {
case FBYTES:
if (off == 0)
break;
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size < off)
off = sbp->st_size;
if (fseeko(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 &&
fseeko(fp, -off, SEEK_END) == -1) {
ierr();
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else {
if (displaybytes(fp, off))
return;
}
break;
case RLINES:
if (S_ISREG(sbp->st_mode)) {
if (!off) {
if (fseek(fp, 0L, SEEK_END) == -1) {
ierr();
return;
}
} else {
if (rlines(fp, off, sbp))
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else {
if (displaylines(fp, off))
return;
}
break;
default:
break;
}
if (fflag) {
kq = kqueue();
if (kq < 0)
xerr(1, "kqueue");
action = ADD_EVENTS;
}
for (;;) {
while ((ch = getc(fp)) != EOF) {
if (putchar(ch) == EOF)
oerr();
}
if (ferror(fp)) {
ierr();
return;
}
(void)fflush(stdout);
if (!fflag)
break;
clearerr(fp);
switch (action) {
case ADD_EVENTS:
n = 0;
memset(ev, 0, sizeof(ev));
if (fflag == 2 && fp != stdin) {
EV_SET(&ev[n], fileno(fp), EVFILT_VNODE,
EV_ADD | EV_ENABLE | EV_CLEAR,
NOTE_DELETE | NOTE_RENAME, 0, 0);
n++;
}
EV_SET(&ev[n], fileno(fp), EVFILT_READ,
EV_ADD | EV_ENABLE, 0, 0, 0);
n++;
if (kevent(kq, ev, n, NULL, 0, NULL) == -1) {
close(kq);
kq = -1;
action = USE_SLEEP;
} else {
action = USE_KQUEUE;
}
break;
case USE_KQUEUE:
if (kevent(kq, NULL, 0, ev, 1, NULL) == -1)
xerr(1, "kevent");
if (ev[0].filter == EVFILT_VNODE) {
/* file was rotated, wait until it reappears */
action = USE_SLEEP;
} else if (ev[0].data < 0) {
/* file shrank, reposition to end */
if (fseek(fp, 0L, SEEK_END) == -1) {
ierr();
return;
}
}
break;
case USE_SLEEP:
/*
* We pause for one second after displaying any data
* that has accumulated since we read the file.
*/
(void) sleep(1);
if (fflag == 2 && fp != stdin &&
stat(fname, &statbuf) != -1) {
if (statbuf.st_ino != sbp->st_ino ||
statbuf.st_dev != sbp->st_dev ||
statbuf.st_rdev != sbp->st_rdev ||
statbuf.st_nlink == 0) {
fp = freopen(fname, "r", fp);
if (fp == NULL) {
ierr();
goto out;
}
*sbp = statbuf;
if (kq != -1)
action = ADD_EVENTS;
} else if (kq != -1)
action = USE_KQUEUE;
}
break;
}
}
out:
if (fflag && kq != -1)
close(kq);
}
/*
* 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(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
{
int ch;
switch(style) {
case FBYTES:
if (off == 0)
break;
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size < off)
off = sbp->st_size;
if (fseeko(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 &&
fseeko(fp, -off, SEEK_END) == -1) {
ierr();
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
if (display_bytes(fp, off))
return;
break;
case RLINES:
if (S_ISREG(sbp->st_mode))
if (!off) {
if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
ierr();
return;
}
} else
rlines(fp, off, sbp);
else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
if (display_lines(fp, off))
return;
break;
case REVERSE:
errx(1, "internal error: forward style cannot be REVERSE");
/* NOTREACHED */
}
while ((ch = getc(fp)) != EOF) {
if (putchar(ch) == EOF)
oerr();
}
if (ferror(fp)) {
ierr();
return;
}
fflush(stdout);
}
