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Flush buffered reads / writes before seeking

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* libguile/ports.c (scm_seek): Flush before seeking on a buffered port.
* libguile/fports.c (fport_seek):
* libguile/strports.c (st_seek): Remove code to flush buffers.
* test-suite/tests/ports.test: Update test expectations that the
  putback buffer is flushed on a seek.  Previously there was a special
  case for SEEK_CUR with an offset of 0 to avoid flushing buffers, but
  that's an arbitrary choice that differs from all other combinations of
  OFFSET and WHENCE.
This commit is contained in:
Andy Wingo 2016-04-04 11:28:28 +02:00
parent b7e49a75a9
commit b77fb752dd
4 changed files with 52 additions and 100 deletions
Download patch file Download diff file Expand all files Collapse all files

42
libguile/fports.c
View file

@ -670,50 +670,12 @@ fport_fill_input (SCM port)
static scm_t_off
fport_seek (SCM port, scm_t_off offset, int whence)
{
scm_t_port *pt = SCM_PTAB_ENTRY (port);
scm_t_fport *fp = SCM_FSTREAM (port);
off_t_or_off64_t rv;
off_t_or_off64_t result;
if (pt->rw_active == SCM_PORT_WRITE)
{
if (offset != 0 || whence != SEEK_CUR)
{
fport_flush (port);
result = rv = lseek_or_lseek64 (fp->fdes, offset, whence);
}
else
{
/* read current position without disturbing the buffer. */
rv = lseek_or_lseek64 (fp->fdes, offset, whence);
result = rv + (pt->write_pos - pt->write_buf);
}
}
else if (pt->rw_active == SCM_PORT_READ)
{
if (offset != 0 || whence != SEEK_CUR)
{
/* could expand to avoid a second seek. */
scm_end_input_unlocked (port);
result = rv = lseek_or_lseek64 (fp->fdes, offset, whence);
}
else
{
/* read current position without disturbing the buffer
(particularly the unread-char buffer). */
rv = lseek_or_lseek64 (fp->fdes, offset, whence);
result = rv - (pt->read_end - pt->read_pos);
result = lseek_or_lseek64 (fp->fdes, offset, whence);
if (pt->read_buf == pt->putback_buf)
result -= pt->saved_read_end - pt->saved_read_pos;
}
}
else /* SCM_PORT_NEITHER */
{
result = rv = lseek_or_lseek64 (fp->fdes, offset, whence);
}
if (rv == -1)
if (result == -1)
scm_syserror ("fport_seek");
return result;

14
libguile/ports.c
View file

@ -2851,15 +2851,25 @@ SCM_DEFINE (scm_seek, "seek", 3, 0, 0,
if (SCM_OPPORTP (fd_port))
{
scm_t_port *pt = SCM_PTAB_ENTRY (fd_port);
scm_t_port_internal *pti = SCM_PORT_GET_INTERNAL (fd_port);
scm_t_ptob_descriptor *ptob = SCM_PORT_DESCRIPTOR (fd_port);
off_t_or_off64_t off = scm_to_off_t_or_off64_t (offset);
off_t_or_off64_t rv;
if (!ptob->seek)
if (!ptob->seek || !pt->rw_random)
SCM_MISC_ERROR ("port is not seekable",
scm_cons (fd_port, SCM_EOL));
else
/* FIXME: Avoid flushing buffers for SEEK_CUR with an offset of
0. */
if (pt->rw_active == SCM_PORT_READ)
scm_end_input_unlocked (pt->port);
else if (pt->rw_active == SCM_PORT_WRITE)
scm_flush_unlocked (pt->port);
pt->rw_active = SCM_PORT_NEITHER;
rv = ptob->seek (fd_port, off, how);
/* Set stream-start flags according to new position. */

24
libguile/strports.c
View file

@ -162,27 +162,6 @@ st_seek (SCM port, scm_t_off offset, int whence)
scm_t_port *pt = SCM_PTAB_ENTRY (port);
scm_t_off target;
if (pt->rw_active == SCM_PORT_READ && offset == 0 && whence == SEEK_CUR)
/* special case to avoid disturbing the unread-char buffer. */
{
if (pt->read_buf == pt->putback_buf)
{
target = pt->saved_read_pos - pt->saved_read_buf
- (pt->read_end - pt->read_pos);
}
else
{
target = pt->read_pos - pt->read_buf;
}
}
else
/* all other cases. */
{
if (pt->rw_active == SCM_PORT_READ)
scm_end_input_unlocked (port);
pt->rw_active = SCM_PORT_NEITHER;
switch (whence)
{
case SEEK_CUR:
@ -213,13 +192,14 @@ st_seek (SCM port, scm_t_off offset, int whence)
else if (target == pt->write_buf_size)
st_resize_port (pt, target * 2);
}
pt->read_pos = pt->write_pos = pt->read_buf + target;
if (pt->read_pos > pt->read_end)
{
pt->read_end = (unsigned char *) pt->read_pos;
pt->read_buf_size = pt->read_end - pt->read_buf;
}
}
return target;
}

8
test-suite/tests/ports.test
View file

@ -176,8 +176,8 @@
(unread-char #\z iport)
(pass-if "file: in tell 0 after unread"
(= (seek iport 0 SEEK_CUR) 0))
(pass-if "file: unread char still there"
(char=? (read-char iport) #\z))
(pass-if "file: putback buffer flushed after seek"
(char=? (read-char iport) #\J))
(seek iport 7 SEEK_SET)
(pass-if "file: in last char"
(char=? (read-char iport) #\x))
@ -700,8 +700,8 @@
(unread-char #\x p)
(pass-if "input tell back to 0"
(= (seek p 0 SEEK_CUR) 0))
(pass-if "input ungetted char"
(char=? (read-char p) #\x))
(pass-if "putback buffer discarded after seek"
(char=? (read-char p) #\t))
(seek p 0 SEEK_END)
(pass-if "input seek to end"
(= (seek p 0 SEEK_CUR)