From 30d412469c930fe4150ad2b9a321eea2747ec6f4 Mon Sep 17 00:00:00 2001
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Mon, 7 May 2012 16:30:37 +0200
Subject: Filesystem: PR1398: Fix lseek() mechanic

According to POSIX the lseek() function shall not, by itself, extend the
size of a file.

Remove the size field of rtems_libio_t.  A file has only one size but
may have multiple open file descriptors.  Thus a file size field in the
file descriptor may lead to inconsistencies.

New default handlers rtems_filesystem_default_lseek_file() and
rtems_filesystem_default_lseek_directory().
---
 cpukit/libcsupport/include/rtems/libio.h | 50 ++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 5 deletions(-)

(limited to 'cpukit/libcsupport/include/rtems/libio.h')

diff --git a/cpukit/libcsupport/include/rtems/libio.h b/cpukit/libcsupport/include/rtems/libio.h
index 04ca52c4aa..a740a408f0 100644
--- a/cpukit/libcsupport/include/rtems/libio.h
+++ b/cpukit/libcsupport/include/rtems/libio.h
@@ -849,8 +849,9 @@ typedef int (*rtems_filesystem_ioctl_t)(
  * @retval non-negative The new offset from the beginning of the file.
  * @retval -1 An error occured.  The errno is set to indicate the error.
  *
- * @see rtems_filesystem_default_lseek() and
- * rtems_filesystem_default_lseek_success().
+ * @see rtems_filesystem_default_lseek(),
+ * rtems_filesystem_default_lseek_file(), and
+ * rtems_filesystem_default_lseek_directory().
  */
 typedef off_t (*rtems_filesystem_lseek_t)(
   rtems_libio_t *iop,
@@ -1025,12 +1026,52 @@ off_t rtems_filesystem_default_lseek(
   int            whence
 );
 
+/**
+ * @brief An offset 0 with a whence of SEEK_SET will perform a directory rewind
+ * operation.
+ *
+ * This function has no protection against concurrent access.
+ *
+ * @retval -1 The offset is not zero or the whence is not SEEK_SET.
+ * @retval 0 Successful rewind operation.
+ *
+ * @see rtems_filesystem_lseek_t.
+ */
+off_t rtems_filesystem_default_lseek_directory(
+  rtems_libio_t *iop,
+  off_t offset,
+  int whence
+);
+
+/**
+ * @brief Default lseek() handler for files.
+ *
+ * The fstat() handler will be used to obtain the file size in case whence is
+ * SEEK_END.
+ *
+ * This function has no protection against concurrent access.
+ *
+ * @retval -1 An error occured.  In case an integer overflow occured, then the
+ * errno will be set to EOVERFLOW.  In case the new offset is negative, then
+ * the errno will be set to EINVAL.  In case the whence is SEEK_END and the
+ * fstat() handler to obtain the current file size returned an error status,
+ * then the errno will be set by the fstat() handler.
+ * @retval offset The new offset.
+ *
+ * @see rtems_filesystem_lseek_t.
+ */
+off_t rtems_filesystem_default_lseek_file(
+  rtems_libio_t *iop,
+  off_t offset,
+  int whence
+);
+
 /**
  * @retval 0 Always.
  *
  * @see rtems_filesystem_lseek_t.
  */
-off_t rtems_filesystem_default_lseek_success(
+off_t rtems_filesystem_default_lseek_file(
   rtems_libio_t *iop,
   off_t          offset,
   int            whence
@@ -1157,11 +1198,10 @@ extern const rtems_filesystem_limits_and_options_t
  * It will be indexed by 'fd'.
  *
  * @todo Should really have a separate per/file data structure that this points
- * to (eg: size, offset, driver, pathname should be in that)
+ * to (eg: offset, driver, pathname should be in that)
  */
 struct rtems_libio_tt {
   rtems_driver_name_t                    *driver;
-  off_t                                   size;      /* size of file */
   off_t                                   offset;    /* current offset into file */
   uint32_t                                flags;
   rtems_filesystem_location_info_t        pathinfo;
-- 
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