sendmail/libsm/fpos.c

/*
 * 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: fpos.c,v 1.39 2005/06/14 23:07:20 ca Exp $")
#include <errno.h>
#include <setjmp.h>
#include <sm/time.h>
#include <sm/heap.h>
#include <sm/signal.h>
#include <sm/clock.h>
#include <sm/io.h>
#include <sm/assert.h>
#include "local.h"

static void tellalrm __P((int));
static jmp_buf TellTimeOut;

/*
**  TELLALRM -- handler when timeout activated for sm_io_tell()
**
**  Returns flow of control to where setjmp(TellTimeOut) was set.
**
**  Parameters:
**      sig -- unused
**
**  Returns:
**      does not return
**
**  Side Effects:
**      returns flow of control to setjmp(TellTimeOut).
**
**  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
tellalrm(sig)
    int sig;
{
    longjmp(TellTimeOut, 1);
}

/*
**  SM_IO_TELL -- position the file pointer
**
**  Paramters:
**      fp -- the file pointer to get repositioned
**      timeout -- time to complete the tell (milliseconds)
**
**  Returns:
**      Success -- the repositioned location.
**      Failure -- -1 (minus 1) and sets errno
*/

long
sm_io_tell(fp, timeout)
    register SM_FILE_T *fp;
    int SM_NONVOLATILE timeout;
{
    register off_t pos;
    SM_EVENT *evt = NULL;

    SM_REQUIRE_ISA(fp, SmFileMagic);
    if (fp->f_seek == NULL)
    {
        errno = ESPIPE;         /* historic practice */
        return -1L;
    }

    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 -1L;
    }

    /*
    **  Find offset of underlying I/O object, then adjust byte position
    **  may adjust seek offset on append stream
    */

    (void) sm_flush(fp, (int *) &timeout);

    /* This is where we start the timeout */
    if (timeout != SM_TIME_FOREVER)
    {
        if (setjmp(TellTimeOut) != 0)
        {
            errno = EAGAIN;
            return -1L;
        }

        evt = sm_seteventm(timeout, tellalrm, 0);
    }

    if (fp->f_flags & SMOFF)
        pos = fp->f_lseekoff;
    else
    {
        /* XXX only set the timeout here? */
        pos = (*fp->f_seek)(fp, (off_t) 0, SM_IO_SEEK_CUR);
        if (pos == -1L)
            goto clean;
    }
    if (fp->f_flags & SMRD)
    {
        /*
        **  Reading.  Any unread characters (including
        **  those from ungetc) cause the position to be
        **  smaller than that in the underlying object.
        */

        pos -= fp->f_r;
        if (HASUB(fp))
            pos -= fp->f_ur;
    }
    else if (fp->f_flags & SMWR && fp->f_p != NULL)
    {
        /*
        **  Writing.  Any buffered characters cause the
        **  position to be greater than that in the
        **  underlying object.
        */

        pos += fp->f_p - fp->f_bf.smb_base;
    }

clean:
    /*  We're back. So undo our timeout and handler */
    if (evt != NULL)
        sm_clrevent(evt);
    return pos;
}