add ftruncate() method

2 files changed, 28 insertions, 4 deletions

diff --git a/include/fuse.h b/include/fuse.h
index 290e9d3..6d7e54b 100644
--- a/include/fuse.h
+++ b/include/fuse.h
@@ -63,9 +63,9 @@ typedef int (*fuse_dirfil_t) (fuse_dirh_t h, const char *name, int type,
  *
  * All methods are optional, but some are essential for a useful
  * filesystem (e.g. getattr).  Open, flush, release, fsync, opendir,
- * releasedir, fsyncdir, access, create, init and destroy are special
- * purpose methods, without which a full featured filesystem can still
- * be implemented.
+ * releasedir, fsyncdir, access, create, ftruncate, init and destroy
+ * are special purpose methods, without which a full featured
+ * filesystem can still be implemented.
  */
 struct fuse_operations {
     /** Get file attributes.
@@ -324,6 +324,20 @@ struct fuse_operations {
      * Introduced in version 2.5
      */
     int (*create) (const char *, mode_t, struct fuse_file_info *);
+
+    /**
+     * Change the size of an open file
+     *
+     * This method is called instead of the truncate() method if the
+     * truncation was invoked from an ftruncate() system call.
+     *
+     * If this method is not implemented or under Linux kernel
+     * versions earlier than 2.6.15, the truncate() method will be
+     * called instead.
+     *
+     * Introduced in version 2.5
+     */
+    int (*ftruncate) (const char *, off_t, struct fuse_file_info *);
 };
 
 /** Extra context that may be needed by some filesystems
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index e9c64ce..a027163 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -198,6 +198,13 @@ struct fuse_lowlevel_ops {
      * bitmask contain valid values.  Other members contain undefined
      * values.
      *
+     * If the setattr was invoked from the ftruncate() system call
+     * under Linux kernel versions 2.6.15 or later, the fi->fh will
+     * contain the value set by the open method or will be undefined
+     * if the open method didn't set any value.  Otherwise (not
+     * ftruncate call, or kernel version earlier than 2.6.15) the fi
+     * parameter will be NULL.
+     *
      * Valid replies:
      *   fuse_reply_attr()
      *   fuse_reply_err()
@@ -206,7 +213,10 @@ struct fuse_lowlevel_ops {
      * @param ino the inode number
      * @param attr the attributes
      * @param to_set bit mask of attributes which should be set
-     * @param fi for future use, currently always NULL
+     * @param fi file information, or NULL
+     *
+     * Changed in version 2.5:
+     *     file information filled in for ftruncate
      */
     void (*setattr) (fuse_req_t req, fuse_ino_t ino, struct stat *attr,
                     int to_set, struct fuse_file_info *fi);