source: trunk/kernel/syscalls/sys_lseek.c @ 5

/*
 * kern/sys_lseek.c - set the read/write offset of an opened file 
 * 
 * Copyright (c) 2008,2009,2010,2011,2012 Ghassan Almaless
 * Copyright (c) 2011,2012 UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-kernel.
 *
 * ALMOS-kernel is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-kernel is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-kernel; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <types.h>
#include <vfs.h>
#include <thread.h>
#include <sys-vfs.h>
#include <task.h>

int sys_lseek (uint_t fd, off_t offset, int whence)
{
        error_t err = 0;
        size_t new_offset;
        struct thread_s *this;
        struct task_s *task;
        struct vfs_file_s *file;

        file = NULL;
        this = current_thread;
        task = current_task;

        /* FIXME: file may be closed in parallel 
         * of seek/read/write/mmap ..etc 
         * so file may be NULL or invalid */
        if((fd >= CONFIG_TASK_FILE_MAX_NR) || (task_fd_lookup(task, fd, &file)))
        {
                this->info.errno = EBADFD;
                return -1;
        }

        if((err = vfs_lseek(file, offset, whence, &new_offset)))
        {
                this->info.errno = (err < 0) ? -err : err;
                return -1;
        }
  
        return new_offset;
}