Add support for bsdiff of file system metadata blocks

utils.h

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__
 
 #include <errno.h>
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
 
 #include <glib.h>
 
+#include <ext2fs/ext2fs.h>
+
 #include "update_engine/action.h"
 #include "update_engine/action_processor.h"
 
 namespace chromeos_update_engine {
 
 namespace utils {
 
 // Returns true if this is an official Chrome OS build, false otherwise.
 bool IsOfficialBuild();
 
@@ skipping 237 matching lines @@
       *fd_ = -1;
     }
   }
   void set_should_close(bool should_close) { should_close_ = should_close; }
  private:
   int* fd_;
   bool should_close_;
   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:
   explicit ScopedPathUnlinker(const std::string& path) : path_(path) {}
   ~ScopedPathUnlinker() {
     if (unlink(path_.c_str()) < 0) {
       std::string err_message = strerror(errno);
       LOG(ERROR) << "Unable to unlink path " << path_ << ": " << err_message;
     }
   }
@@ skipping 98 matching lines @@
 
 #define TEST_AND_RETURN(_x)                                                    \
   do {                                                                         \
     bool _success = (_x);                                                      \
     if (!_success) {                                                           \
       LOG(ERROR) << #_x " failed.";                                            \
       return;                                                                  \
     }                                                                          \
   } 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__