AU: Add a utility routine to get the filesystem size from a device.

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>
@@ skipping 97 matching lines @@
 // Returns true if the root |device| (e.g., "/dev/sdb") is known to be
 // removable, false otherwise.
 bool IsRemovableDevice(const std::string& device);
 
 // Synchronously mount or unmount a filesystem. Return true on success.
 // Mounts as ext3 with default options.
 bool MountFilesystem(const std::string& device, const std::string& mountpoint,
                      unsigned long flags);
 bool UnmountFilesystem(const std::string& mountpoint);
 
+// Returns the block count and the block byte size of the ext3 file system on
+// |device| (which may be a real device or a path to a filesystem image) or on
+// an opened file descriptor |fd|. The actual file-system size is |block_count|
+// * |block_size| bytes. Returns true on success, false otherwise.
+bool GetFilesystemSize(const std::string& device,
+                       int* out_block_count,
+                       int* out_block_size);
+bool GetFilesystemSizeFromFD(int fd,
+                             int* out_block_count,
+                             int* out_block_size);
+
 enum BootLoader {
   BootLoader_SYSLINUX = 0,
   BootLoader_CHROME_FIRMWARE = 1
 };
 // Detects which bootloader this system uses and returns it via the out
 // param. Returns true on success.
 bool GetBootloader(BootLoader* out_bootloader);
 
 // Returns the error message, if any, from a GError pointer.
 const char* GetGErrorMessage(const GError* error);
@@ skipping 222 matching lines @@
     bool _success = (_x);                                                      \
     if (!_success) {                                                           \
       LOG(ERROR) << #_x " failed.";                                            \
       return;                                                                  \
     }                                                                          \
   } while (0)
 
 
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__