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/****************************************************************************
* fs/fs_lseek.c
*
* Copyright (C) 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>
#include "fs_internal.h"
#if CONFIG_NFILE_DESCRIPTORS > 0
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: lseek
*
* Description:
* The lseek() function repositions the offset of the open file associated
* with the file descriptor fildes to the argument 'offset' according to the
* directive 'whence' as follows:
*
* SEEK_SET
* The offset is set to offset bytes.
* SEEK_CUR
* The offset is set to its current location plus offset bytes.
* SEEK_END
* The offset is set to the size of the file plus offset bytes.
*
* The lseek() function allows the file offset to be set beyond the end of the
* file (but this does not change the size of the file). If data is later written
* at this point, subsequent reads of the data in the gap (a "hole") return null
* bytes ('\0') until data is actually written into the gap.
*
* Parameters:
* fd File descriptor of device
* offset Defines the offset to position to
* whence Defines how to use offset
*
* Return:
* The resulting offset on success. -1 on failure withi errno set properly:
*
* EBADF fildes is not an open file descriptor.
* EINVAL whence is not one of SEEK_SET, SEEK_CUR, SEEK_END; or the
* resulting file offset would be negative, or beyond the end of a
* seekable device.
* EOVERFLOW The resulting file offset cannot be represented in an off_t.
* ESPIPE fildes is associated with a pipe, socket, or FIFO.
*
****************************************************************************/
off_t lseek(int fd, off_t offset, int whence)
{
FAR struct filelist *list;
FAR struct file *filep;
FAR struct inode *inode;
int err;
/* Did we get a valid file descriptor? */
if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
{
err = EBADF;
goto errout;
}
/* Get the thread-specific file list */
list = sched_getfiles();
if (!list)
{
err = EMFILE;
goto errout;
}
/* Is a driver registered? */
filep = &list->fl_files[fd];
inode = filep->f_inode;
if (inode && inode->u.i_ops)
{
/* Does it support the seek method */
if (inode->u.i_ops->seek)
{
/* Yes, then let it perform the seek */
err = (int)inode->u.i_ops->seek(filep, offset, whence);
if (err < 0)
{
err = -err;
goto errout;
}
}
else
{
/* No... there are a couple of default actions we can take */
switch (whence)
{
case SEEK_CUR:
offset += filep->f_pos;
case SEEK_SET:
if (offset >= 0)
{
filep->f_pos = offset; /* Might be beyond the end-of-file */
break;
}
else
{
err = EINVAL;
goto errout;
}
break;
case SEEK_END:
err = ENOSYS;
goto errout;
default:
err = EINVAL;
goto errout;
}
}
}
return filep->f_pos;
errout:
set_errno(err);
return (off_t)ERROR;
}
#endif
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