forked from Archive/PX4-Autopilot
177 lines
5.5 KiB
C
177 lines
5.5 KiB
C
/****************************************************************************
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* fs/fs_lseek.c
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*
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* Copyright (C) 2008 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <sched.h>
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#include <errno.h>
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#include "fs_internal.h"
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#if CONFIG_NFILE_DESCRIPTORS > 0
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: lseek
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*
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* Description:
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* The lseek() function repositions the offset of the open file associated
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* with the file descriptor fildes to the argument 'offset' according to the
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* directive 'whence' as follows:
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*
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* SEEK_SET
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* The offset is set to offset bytes.
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* SEEK_CUR
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* The offset is set to its current location plus offset bytes.
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* SEEK_END
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* The offset is set to the size of the file plus offset bytes.
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*
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* The lseek() function allows the file offset to be set beyond the end of the
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* file (but this does not change the size of the file). If data is later written
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* at this point, subsequent reads of the data in the gap (a "hole") return null
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* bytes ('\0') until data is actually written into the gap.
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*
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* Parameters:
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* fd File descriptor of device
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* offset Defines the offset to position to
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* whence Defines how to use offset
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*
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* Return:
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* The resulting offset on success. -1 on failure withi errno set properly:
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*
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* EBADF fildes is not an open file descriptor.
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* EINVAL whence is not one of SEEK_SET, SEEK_CUR, SEEK_END; or the
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* resulting file offset would be negative, or beyond the end of a
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* seekable device.
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* EOVERFLOW The resulting file offset cannot be represented in an off_t.
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* ESPIPE fildes is associated with a pipe, socket, or FIFO.
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*
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****************************************************************************/
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off_t lseek(int fd, off_t offset, int whence)
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{
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FAR struct filelist *list;
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FAR struct file *filep;
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FAR struct inode *inode;
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int err;
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/* Did we get a valid file descriptor? */
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if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
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{
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err = EBADF;
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goto errout;
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}
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/* Get the thread-specific file list */
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list = sched_getfiles();
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if (!list)
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{
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err = EMFILE;
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goto errout;
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}
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/* Is a driver registered? */
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filep = &list->fl_files[fd];
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inode = filep->f_inode;
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if (inode && inode->u.i_ops)
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{
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/* Does it support the seek method */
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if (inode->u.i_ops->seek)
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{
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/* Yes, then let it perform the seek */
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err = (int)inode->u.i_ops->seek(filep, offset, whence);
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if (err < 0)
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{
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err = -err;
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goto errout;
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}
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}
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else
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{
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/* No... there are a couple of default actions we can take */
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switch (whence)
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{
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case SEEK_CUR:
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offset += filep->f_pos;
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case SEEK_SET:
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if (offset >= 0)
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{
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filep->f_pos = offset; /* Might be beyond the end-of-file */
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break;
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}
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else
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{
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err = EINVAL;
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goto errout;
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}
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break;
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case SEEK_END:
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err = ENOSYS;
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goto errout;
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default:
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err = EINVAL;
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goto errout;
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}
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}
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}
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return filep->f_pos;
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errout:
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set_errno(err);
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return (off_t)ERROR;
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}
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#endif
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