[Libsysio-commit] HEAD: libsysio/include file.h

[Lee W. <lw...@us...>]

Update of /cvsroot/libsysio/libsysio/include
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv6661/include

Modified Files:
	file.h 
Log Message:


Add a new macro, F_CHKRW, that given a pointer to an open file table entry
and one of 'r' or 'w' will return:

	0	if the access is permitted against the open file
	-EBADF	if not opened for the desired access
	-EROFS	if 'w' and the file system was mounted read-only

Then, using the new macro, implemented a check for the truncate/ftruncate
calls to assure the file and mount will permit the operation before
attempting it against the lower-level driver.


Index: file.h
===================================================================
RCS file: /cvsroot/libsysio/libsysio/include/file.h,v
retrieving revision 1.13
retrieving revision 1.14
diff -u -w -b -B -p -r1.13 -r1.14
--- file.h	31 Oct 2005 19:47:42 -0000	1.13
+++ file.h	10 Apr 2006 23:25:54 -0000	1.14
@@ -112,6 +112,22 @@ struct file {
 		(fil)->f_flags = (flags); \
 	} while (0)
 
+/*
+ * Determine if a file may be read/written.
+ *
+ * Give it the open file table ptr and a character indicating read, 'r', or
+ * write 'w'. It will return 0 if that access is permitted or -EBADF, if not.
+ */
+
+#define F_CHKRW(_fil, _c) \
+	((_c) == O_RDONLY \
+	   ? (((_fil)->f_flags & O_RDONLY || (_fil)->f_flags & O_RDWR) \
+	       ? 0 \
+	       : -EBADF) \
+	   : (((_fil)->f_flags & O_WRONLY || (_fil)->f_flags & O_RDWR) \
+	       ? (IS_RDONLY(NULL, (_fil)->f_ino) ? -EROFS : 0) \
+	       : -EBADF))
+
 struct ioctx;
 
 extern struct file *_sysio_fnew(struct inode *ino, int flags);