adtools/clib2

/*
 * $Id: fcntl_lseek.c,v 1.11 2006-01-08 12:04:22 obarthel Exp $
 *
 * :ts=4
 *
 * Portable ISO 'C' (1994) runtime library for the Amiga computer
 * Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Neither the name of Olaf Barthel nor the names of contributors
 *     may be used to endorse or promote products derived from this
 *     software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _FCNTL_HEADERS_H
#include "fcntl_headers.h"
#endif /* _FCNTL_HEADERS_H */

/****************************************************************************/

/* The following is not part of the ISO 'C' (1994) standard. */

/****************************************************************************/

off_t
lseek(int file_descriptor, off_t offset, int mode)
{
    struct file_action_message fam;
    off_t result = SEEK_ERROR;
    struct fd * fd = NULL;
    off_t position;

    ENTER();

    SHOWVALUE(file_descriptor);
    SHOWVALUE(offset);
    SHOWVALUE(mode);

    assert( file_descriptor >= 0 && file_descriptor < __num_fd );
    assert( __fd[file_descriptor] != NULL );
    assert( FLAG_IS_SET(__fd[file_descriptor]->fd_Flags,FDF_IN_USE) );

    if(__check_abort_enabled)
        __check_abort();

    __stdio_lock();

    fd = __get_file_descriptor(file_descriptor);
    if(fd == NULL)
    {
        __set_errno(EBADF);
        goto out;
    }

    __fd_lock(fd);

    if(mode < SEEK_SET || mode > SEEK_END)
    {
        SHOWMSG("seek mode is invalid");

        __set_errno(EINVAL);
        goto out;
    }

    fam.fam_Action    = file_action_seek;
    fam.fam_Offset    = offset;
    fam.fam_Mode    = mode;

    assert( fd->fd_Action != NULL );

    /* Note that a return value of -1 (= SEEK_ERROR) may be a
       valid file position in files larger than 2 GBytes. Just
       to be sure, we therefore also check the secondary error
       to verify that what could be a file position is really
       an error indication. */
    position = (*fd->fd_Action)(fd,&fam);
    if(position == SEEK_ERROR && fam.fam_Error != OK)
    {
        __set_errno(fam.fam_Error);
        goto out;
    }

    /* If this is a valid file position, clear 'errno' so that
       it cannot be mistaken for an error. */
    if(position < 0)
        __set_errno(OK);

    result = position;

 out:

    __fd_unlock(fd);

    __stdio_unlock();

    RETURN(result);
    return(result);
}