Add the methods to change and get a posix file permission to file_util.

base/file_util_posix.cc

Index: base/file_util_posix.cc
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index e3bab95dd8e32554c81d8b41466909e5406e0027..96760832b5b1f19f2de15987f2395be87d3b8eb7 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -457,6 +457,39 @@ bool ReadSymbolicLink(const FilePath& symlink_path,
   return true;
 }
 
+bool GetPosixFilePermissions(const FilePath& path, mode_t* mode) {
+  base::ThreadRestrictions::AssertIOAllowed();
+  DCHECK(mode);
+
+  stat_wrapper_t file_info;
+  if (CallStat(path.value().c_str(), &file_info) != 0)

[satorux1, 2012/07/03 06:16:55]

i think there is a reason not to use lstat here. please add some comment

per http://linux.die.net/man/2/lstat, permission bits in st_mode are invalid
with lstat(2):


According to POSIX.1-2001, lstat() on a symbolic link need return valid
information only in the st_size field and the file-type component of the st_mode
field of the stat structure. POSIX.-2008 tightens the specification, requiring
lstat() to return valid information in all fields except the permission bits in
st_mode.

[yoshiki, 2012/07/04 07:57:57]

Done.

+    return false;
+
+  *mode = file_info.st_mode;
+  return true;
+}
+
+bool ChangePosixFilePermissions(const FilePath& path,
+                                mode_t mode_bits_to_set,
+                                mode_t mode_bits_to_clear) {
+  base::ThreadRestrictions::AssertIOAllowed();
+  DCHECK(!(mode_bits_to_set & mode_bits_to_clear))
+      << "Can't set and clear the same bits.";
+
+  stat_wrapper_t stat_buf;
+  if (CallLstat(path.value().c_str(), &stat_buf) != 0)

[satorux1, 2012/07/03 06:16:55]

why lstat? it seems lstat on symbolic link is invalid

[satorux1, 2012/07/03 06:22:36]

invalid for permission bits

[yoshiki, 2012/07/04 07:57:57]

Sorry, I made a mistake.

On 2012/07/03 06:16:55, satorux1 wrote:

+    return false;
+
+  mode_t updated_mode_bits = stat_buf.st_mode;
+  updated_mode_bits |= mode_bits_to_set;
+  updated_mode_bits &= ~mode_bits_to_clear;
+
+  if (chmod(path.value().c_str(), updated_mode_bits) != 0)

[satorux1, 2012/07/03 06:23:29]

please use HANDLE_EINTR when you call a system call

[yoshiki, 2012/07/04 07:57:57]

Done.

+    return false;
+
+  return true;
+}
+
 // Creates and opens a temporary file in |directory|, returning the
 // file descriptor. |path| is set to the temporary file path.
 // This function does NOT unlink() the file.