diff --git a/common/utils.cc b/common/utils.cc
index f651823..68cad51 100644
--- a/common/utils.cc
+++ b/common/utils.cc
@@ -291,7 +291,10 @@
   return true;
 }
 
-bool PReadAll(const FileDescriptorPtr& fd, void* buf, size_t count, off_t offset,
+bool PReadAll(const FileDescriptorPtr& fd,
+              void* buf,
+              size_t count,
+              off_t offset,
               ssize_t* out_bytes_read) {
   TEST_AND_RETURN_FALSE_ERRNO(fd->Seek(offset, SEEK_SET) !=
                               static_cast<off_t>(-1));
@@ -1067,6 +1070,18 @@
   return true;
 }
 
+int VersionPrefix(const std::string& version) {
+  if (version.empty()) {
+    return 0;
+  }
+  vector<string> tokens = base::SplitString(
+      version, ".", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL);
+  int value;
+  if (tokens.empty() || !base::StringToInt(tokens[0], &value))
+    return -1;  // Target version is invalid.
+  return value;
+}
+
 }  // namespace utils
 
 }  // namespace chromeos_update_engine