diff -r 000000000000 -r 6474c204b198 xpcom/glue/nsVersionComparator.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/glue/nsVersionComparator.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,149 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsVersionComparator_h__
+#define nsVersionComparator_h__
+
+#include "nscore.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#if defined(XP_WIN) && !defined(UPDATER_NO_STRING_GLUE_STL)
+#include <wchar.h>
+#include "nsStringGlue.h"
+#endif
+
+/**
+ * In order to compare version numbers in Mozilla, you need to use the
+ * mozilla::Version class.  You can construct an object of this type by passing
+ * in a string version number to the constructor.  Objects of this type can be
+ * compared using the standard comparison operators.
+ *
+ * For example, let's say that you want to make sure that a given version
+ * number is not older than 15.a2.  Here's how you would write a function to
+ * do that.
+ *
+ * bool IsVersionValid(const char* version) {
+ *   return mozilla::Version("15.a2") <= mozilla::Version(version);
+ * }
+ *
+ * Or, since Version's constructor is implicit, you can simplify this code:
+ *
+ * bool IsVersionValid(const char* version) {
+ *   return mozilla::Version("15.a2") <= version;
+ * }
+ *
+ * On Windows, if your version strings are wide characters, you should use the
+ * mozilla::VersionW variant instead.  The semantics of that class is the same
+ * as Version.
+ */
+
+namespace mozilla {
+
+int32_t NS_COM_GLUE
+CompareVersions(const char *A, const char *B);
+
+#ifdef XP_WIN
+int32_t NS_COM_GLUE
+CompareVersions(const char16_t *A, const char16_t *B);
+#endif
+
+struct NS_COM_GLUE Version
+{
+  Version(const char* versionString)
+  {
+    versionContent = strdup(versionString);
+  }
+
+  const char* ReadContent() const
+  {
+    return versionContent;
+  }
+
+  ~Version()
+  {
+    free(versionContent);
+  }
+
+  bool operator< (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) == -1;
+  }
+  bool operator<= (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) < 1;
+  }
+  bool operator> (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) == 1;
+  }
+  bool operator>= (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) > -1;
+  }
+  bool operator== (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) == 0;
+  }
+  bool operator!= (const Version& rhs) const
+  {
+    return CompareVersions(versionContent, rhs.ReadContent()) != 0;
+  }
+
+ private:
+  char* versionContent;
+};
+
+#ifdef XP_WIN
+struct NS_COM_GLUE VersionW
+{
+  VersionW(const char16_t *versionStringW)
+  {
+    versionContentW = reinterpret_cast<char16_t*>(wcsdup(char16ptr_t(versionStringW)));
+  }
+
+  const char16_t* ReadContentW() const
+  {
+    return versionContentW;
+  }
+
+  ~VersionW()
+  {
+    free(versionContentW);
+  }
+
+  bool operator< (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) == -1;
+  }
+  bool operator<= (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) < 1;
+  }
+  bool operator> (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) == 1;
+  }
+  bool operator>= (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) > -1;
+  }
+  bool operator== (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) == 0;
+  }
+  bool operator!= (const VersionW& rhs) const
+  {
+    return CompareVersions(versionContentW, rhs.ReadContentW()) != 0;
+  }
+
+ private:
+  char16_t* versionContentW;
+};
+#endif
+
+} // namespace mozilla
+
+#endif // nsVersionComparator_h__
+