Add support for bsdiff of file system metadata blocks

utils.h

Index: utils.h
diff --git a/utils.h b/utils.h
index 34b862e109195ec393e81fdbc9562679bb791a90..ad7946d75998ba45b458f29f863a2f7dbeb88d4a 100644
--- a/utils.h
+++ b/utils.h
@@ -14,6 +14,8 @@
 
 #include <glib.h>
 
+#include <ext2fs/ext2fs.h>
+
 #include "update_engine/action.h"
 #include "update_engine/action_processor.h"
 
@@ -271,6 +273,15 @@ class ScopedFdCloser {
   DISALLOW_COPY_AND_ASSIGN(ScopedFdCloser);
 };
 
+// Utility class to close a file system
+class ScopedExt2fsCloser {
+ public:
+  explicit ScopedExt2fsCloser(ext2_filsys filsys) : filsys_(filsys) {}
+  ~ScopedExt2fsCloser() { ext2fs_close(filsys_); }
+ private:
+  ext2_filsys filsys_;
+};
+
 // Utility class to delete a file when it goes out of scope.
 class ScopedPathUnlinker {
  public:
@@ -389,6 +400,16 @@ class ScopedActionCompleter {
     }                                                                          \
   } while (0)
 
+#define TEST_AND_RETURN_FALSE_ERRCODE(_x)                                      \
+  do {                                                                         \
+    errcode_t _error = (_x);                                                   \
+    if (_error) {                                                              \
+      errno = _error;                                                          \
+      LOG(ERROR) << #_x " failed: " << _error;                                 \
+      return false;                                                            \
+    }                                                                          \
+  } while (0)
+
 
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__