/*
* ftello: return current offset.
*/
off_t
ftello(FILE *fp)
{
fpos_t rv;
int ret;
FLOCKFILE(fp);
ret = _ftello(fp, &rv);
FUNLOCKFILE(fp);
if (ret)
return (-1);
if (rv < 0) { /* Unspecified value because of ungetc() at 0 */
errno = ESPIPE;
return (-1);
}
return (rv);
}
/*
* Seek the given file to the given offset.
* `Whence' must be one of the three SEEK_* macros.
*/
int
_fseeko(FILE *fp, off_t offset, int whence, int ltest)
{
fpos_t (*seekfn)(void *, fpos_t, int);
fpos_t target, curoff, ret;
size_t n;
struct stat st;
int havepos;
/*
* Have to be able to seek.
*/
if ((seekfn = fp->_seek) == NULL) {
errno = ESPIPE; /* historic practice */
return (-1);
}
/*
* Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
* After this, whence is either SEEK_SET or SEEK_END.
*/
switch (whence) {
case SEEK_CUR:
/*
* In order to seek relative to the current stream offset,
* we have to first find the current stream offset via
* ftell (see ftell for details).
*/
if (_ftello(fp, &curoff))
return (-1);
if (curoff < 0) {
/* Unspecified position because of ungetc() at 0 */
errno = ESPIPE;
return (-1);
}
if (offset > 0 && curoff > OFF_MAX - offset) {
errno = EOVERFLOW;
return (-1);
}
offset += curoff;
if (offset < 0) {
errno = EINVAL;
return (-1);
}
if (ltest && offset > LONG_MAX) {
errno = EOVERFLOW;
return (-1);
}
whence = SEEK_SET;
havepos = 1;
break;
case SEEK_SET:
if (offset < 0) {
errno = EINVAL;
return (-1);
}
case SEEK_END:
curoff = 0; /* XXX just to keep gcc quiet */
havepos = 0;
break;
default:
errno = EINVAL;
return (-1);
}
/*
* Can only optimise if:
* reading (and not reading-and-writing);
* not unbuffered; and
* this is a `regular' Unix file (and hence seekfn==__sseek).
* We must check __NBF first, because it is possible to have __NBF
* and __SOPT both set.
*/
if (fp->_bf._base == NULL)
__smakebuf(fp);
if (fp->pub._flags & (__SWR | __SRW | __SNBF | __SNPT))
goto dumb;
if ((fp->pub._flags & __SOPT) == 0) {
if (seekfn != __sseek ||
fp->pub._fileno < 0 || _fstat(fp->pub._fileno, &st) ||
(st.st_mode & S_IFMT) != S_IFREG) {
fp->pub._flags |= __SNPT;
goto dumb;
}
fp->_blksize = st.st_blksize;
fp->pub._flags |= __SOPT;
}
/*
* We are reading; we can try to optimise.
* Figure out where we are going and where we are now.
*/
if (whence == SEEK_SET)
target = offset;
else {
if (_fstat(fp->pub._fileno, &st))
goto dumb;
if (offset > 0 && st.st_size > OFF_MAX - offset) {
errno = EOVERFLOW;
return (-1);
}
target = st.st_size + offset;
if ((off_t)target < 0) {
errno = EINVAL;
return (-1);
}
if (ltest && (off_t)target > LONG_MAX) {
errno = EOVERFLOW;
return (-1);
}
}
if (!havepos && _ftello(fp, &curoff))
goto dumb;
/*
* (If the buffer was modified, we have to
* skip this; see fgetln.c.)
*/
if (fp->pub._flags & __SMOD)
goto abspos;
/*
* Compute the number of bytes in the input buffer (pretending
* that any ungetc() input has been discarded). Adjust current
* offset backwards by this count so that it represents the
* file offset for the first byte in the current input buffer.
*/
if (HASUB(fp)) {
curoff += fp->pub._r; /* kill off ungetc */
n = fp->_up - fp->_bf._base;
curoff -= n;
n += fp->_ur;
} else {
n = fp->pub._p - fp->_bf._base;
curoff -= n;
n += fp->pub._r;
}
/*
* If the target offset is within the current buffer,
* simply adjust the pointers, clear EOF, undo ungetc(),
* and return.
*/
if (target >= curoff && target < curoff + n) {
size_t o = target - curoff;
fp->pub._p = fp->_bf._base + o;
fp->pub._r = n - o;
if (HASUB(fp))
FREEUB(fp);
fp->pub._flags &= ~__SEOF;
memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
return (0);
}
abspos:
/*
* The place we want to get to is not within the current buffer,
* but we can still be kind to the kernel copyout mechanism.
* By aligning the file offset to a block boundary, we can let
* the kernel use the VM hardware to map pages instead of
* copying bytes laboriously. Using a block boundary also
* ensures that we only read one block, rather than two.
*/
curoff = target & ~(fp->_blksize - 1);
if (_sseek(fp, curoff, SEEK_SET) == POS_ERR)
goto dumb;
fp->pub._r = 0;
fp->pub._p = fp->_bf._base;
if (HASUB(fp))
FREEUB(fp);
n = target - curoff;
if (n) {
if (__srefill(fp) || fp->pub._r < n)
goto dumb;
fp->pub._p += n;
fp->pub._r -= n;
}
fp->pub._flags &= ~__SEOF;
memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
return (0);
/*
* We get here if we cannot optimise the seek ... just
* do it. Allow the seek function to change fp->_bf._base.
*/
dumb:
if (__sflush(fp) ||
(ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR)
return (-1);
if (ltest && ret > LONG_MAX) {
fp->pub._flags |= __SERR;
errno = EOVERFLOW;
return (-1);
}
/* success: clear EOF indicator and discard ungetc() data */
if (HASUB(fp))
FREEUB(fp);
fp->pub._p = fp->_bf._base;
fp->pub._r = 0;
/* fp->pub._w = 0; */ /* unnecessary (I think...) */
fp->pub._flags &= ~__SEOF;
memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
return (0);
}
