/*
* Copyright (c) 2000-2001, 2004 Sendmail, Inc. and its suppliers.
* All rights reserved.
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* By using this file, you agree to the terms and conditions set
* forth in the LICENSE file which can be found at the top level of
* the sendmail distribution.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include <sm/gen.h>
SM_RCSID("@(#)$Id: fseek.c,v 1.47 2005/06/14 23:07:20 ca Exp $")
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>
#include <setjmp.h>
#include <sm/time.h>
#include <sm/signal.h>
#include <sm/io.h>
#include <sm/assert.h>
#include <sm/clock.h>
#include "local.h"
#define POS_ERR (-(off_t)1)
static void seekalrm __P((int));
static jmp_buf SeekTimeOut;
/*
** SEEKALRM -- handler when timeout activated for sm_io_seek()
**
** Returns flow of control to where setjmp(SeekTimeOut) was set.
**
** Parameters:
** sig -- unused
**
** Returns:
** does not return
**
** Side Effects:
** returns flow of control to setjmp(SeekTimeOut).
**
** NOTE: THIS CAN BE CALLED FROM A SIGNAL HANDLER. DO NOT ADD
** ANYTHING TO THIS ROUTINE UNLESS YOU KNOW WHAT YOU ARE
** DOING.
*/
/* ARGSUSED0 */
static void
seekalrm(sig)
int sig;
{
longjmp(SeekTimeOut, 1);
}
/*
** SM_IO_SEEK -- position the file pointer
**
** Parameters:
** fp -- the file pointer to be seek'd
** timeout -- time to complete seek (milliseconds)
** offset -- seek offset based on 'whence'
** whence -- indicates where seek is relative from.
** One of SM_IO_SEEK_{CUR,SET,END}.
** Returns:
** Failure: returns -1 (minus 1) and sets errno
** Success: returns 0 (zero)
*/
int
sm_io_seek(fp, timeout, offset, whence)
register SM_FILE_T *fp;
int SM_NONVOLATILE timeout;
long SM_NONVOLATILE offset;
int SM_NONVOLATILE whence;
{
bool havepos;
off_t target, curoff;
size_t n;
struct stat st;
int ret;
SM_EVENT *evt = NULL;
register off_t (*seekfn) __P((SM_FILE_T *, off_t, int));
SM_REQUIRE_ISA(fp, SmFileMagic);
/* make sure stdio is set up */
if (!Sm_IO_DidInit)
sm_init();
/* Have to be able to seek. */
if ((seekfn = fp->f_seek) == NULL)
{
errno = ESPIPE; /* historic practice */
return -1;
}
if (timeout == SM_TIME_DEFAULT)
timeout = fp->f_timeout;
if (timeout == SM_TIME_IMMEDIATE)
{
/*
** Filling the buffer will take time and we are wanted to
** return immediately. So...
*/
errno = EAGAIN;
return -1;
}
#define SM_SET_ALARM() \
if (timeout != SM_TIME_FOREVER) \
{ \
if (setjmp(SeekTimeOut) != 0) \
{ \
errno = EAGAIN; \
return -1; \
} \
evt = sm_seteventm(timeout, seekalrm, 0); \
}
/*
** Change any SM_IO_SEEK_CUR to SM_IO_SEEK_SET, and check `whence'
** argument. After this, whence is either SM_IO_SEEK_SET or
** SM_IO_SEEK_END.
*/
switch (whence)
{
case SM_IO_SEEK_CUR:
/*
** In order to seek relative to the current stream offset,
** we have to first find the current stream offset a la
** ftell (see ftell for details).
*/
/* may adjust seek offset on append stream */
sm_flush(fp, (int *) &timeout);
SM_SET_ALARM();
if (fp->f_flags & SMOFF)
curoff = fp->f_lseekoff;
else
{
curoff = (*seekfn)(fp, (off_t) 0, SM_IO_SEEK_CUR);
if (curoff == -1L)
{
ret = -1;
goto clean;
}
}
if (fp->f_flags & SMRD)
{
curoff -= fp->f_r;
if (HASUB(fp))
curoff -= fp->f_ur;
}
else if (fp->f_flags & SMWR && fp->f_p != NULL)
curoff += fp->f_p - fp->f_bf.smb_base;
offset += curoff;
whence = SM_IO_SEEK_SET;
havepos = true;
break;
case SM_IO_SEEK_SET:
case SM_IO_SEEK_END:
SM_SET_ALARM();
curoff = 0; /* XXX just to keep gcc quiet */
havepos = false;
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==sm_stdseek).
** We must check SMNBF first, because it is possible to have SMNBF
** and SMSOPT both set.
*/
if (fp->f_bf.smb_base == NULL)
sm_makebuf(fp);
if (fp->f_flags & (SMWR | SMRW | SMNBF | SMNPT))
goto dumb;
if ((fp->f_flags & SMOPT) == 0)
{
if (seekfn != sm_stdseek ||
fp->f_file < 0 || fstat(fp->f_file, &st) ||
(st.st_mode & S_IFMT) != S_IFREG)
{
fp->f_flags |= SMNPT;
goto dumb;
}
fp->f_blksize = st.st_blksize;
fp->f_flags |= SMOPT;
}
/*
** We are reading; we can try to optimise.
** Figure out where we are going and where we are now.
*/
if (whence == SM_IO_SEEK_SET)
target = offset;
else
{
if (fstat(fp->f_file, &st))
goto dumb;
target = st.st_size + offset;
}
if (!havepos)
{
if (fp->f_flags & SMOFF)
curoff = fp->f_lseekoff;
else
{
curoff = (*seekfn)(fp, (off_t) 0, SM_IO_SEEK_CUR);
if (curoff == POS_ERR)
goto dumb;
}
curoff -= fp->f_r;
if (HASUB(fp))
curoff -= fp->f_ur;
}
/*
** 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->f_r; /* kill off ungetc */
n = fp->f_up - fp->f_bf.smb_base;
curoff -= n;
n += fp->f_ur;
}
else
{
n = fp->f_p - fp->f_bf.smb_base;
curoff -= n;
n += fp->f_r;
}
/*
** If the target offset is within the current buffer,
** simply adjust the pointers, clear SMFEOF, undo ungetc(),
** and return. (If the buffer was modified, we have to
** skip this; see getln in fget.c.)
*/
if (target >= curoff && target < curoff + (off_t) n)
{
register int o = target - curoff;
fp->f_p = fp->f_bf.smb_base + o;
fp->f_r = n - o;
if (HASUB(fp))
FREEUB(fp);
fp->f_flags &= ~SMFEOF;
ret = 0;
goto clean;
}
/*
** 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->f_blksize - 1);
if ((*seekfn)(fp, curoff, SM_IO_SEEK_SET) == POS_ERR)
goto dumb;
fp->f_r = 0;
fp->f_p = fp->f_bf.smb_base;
if (HASUB(fp))
FREEUB(fp);
fp->f_flags &= ~SMFEOF;
n = target - curoff;
if (n)
{
/* Note: SM_TIME_FOREVER since fn timeout already set */
if (sm_refill(fp, SM_TIME_FOREVER) || fp->f_r < (int) n)
goto dumb;
fp->f_p += n;
fp->f_r -= n;
}
ret = 0;
clean:
/* We're back. So undo our timeout and handler */
if (evt != NULL)
sm_clrevent(evt);
return ret;
dumb:
/*
** We get here if we cannot optimise the seek ... just
** do it. Allow the seek function to change fp->f_bf.smb_base.
*/
/* Note: SM_TIME_FOREVER since fn timeout already set */
ret = SM_TIME_FOREVER;
if (sm_flush(fp, &ret) != 0 ||
(*seekfn)(fp, (off_t) offset, whence) == POS_ERR)
{
ret = -1;
goto clean;
}
/* success: clear SMFEOF indicator and discard ungetc() data */
if (HASUB(fp))
FREEUB(fp);
fp->f_p = fp->f_bf.smb_base;
fp->f_r = 0;
fp->f_flags &= ~SMFEOF;
ret = 0;
goto clean;
}