Added lseek()

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@612 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 179 insertions, 0 deletions

diff --git a/nuttx/fs/fs_lseek.c b/nuttx/fs/fs_lseek.c
new file mode 100644
index 000000000..8131acf68
--- /dev/null
+++ b/nuttx/fs/fs_lseek.c
@@ -0,0 +1,179 @@
+/****************************************************************************
+ * fs/fs_lseek.c
+ *
+ *   Copyright (C) 2008 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Compilation Switches
+ ****************************************************************************/
+
+/****************************************************************************
+ * 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:
+  *get_errno_ptr() = err;
+  return (off_t)ERROR;
+}
+#endif
+