diff options
Diffstat (limited to 'nuttx/fs/fs_lseek.c')
-rw-r--r-- | nuttx/fs/fs_lseek.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/nuttx/fs/fs_lseek.c b/nuttx/fs/fs_lseek.c new file mode 100644 index 000000000..c57658434 --- /dev/null +++ b/nuttx/fs/fs_lseek.c @@ -0,0 +1,176 @@ +/**************************************************************************** + * 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 |