Issue #41 - Bring method of determining IE version up to date

src/shared/IE_version.cpp

+#include "IE_version.h"
+#include "Registry.h"
+#include <cstdlib>
+
+using namespace AdblockPlus;
+
+/**
+ * Internal implementation of the IE version string.
+ *
+ * This version throws exceptions for its errors, relying on its caller to handle them.
+ *
+ * Quoting http://support.microsoft.com/kb/969393:
+ *   "Note The version string value for Internet Explorer 10 is 9.10.9200.16384, and the svcVersion string value is 10.0.9200.16384."
+ * [EH 2014-06-20] My current version of IE 11 is reporting these values:
+ *   Version 9.11.9600.17041
+ *   svcVersion 11.0.9600.17041
+ *
+ * Warning: IE version 12 and later might not behave the same, so this function should be reviewed with each new release.
+ *
+ * \par postcondition
+ *   Return value matches regex `^[0-9]{1,2}\.$`; this is a sanity check on the format.
+ */
+std::wstring IE_version_string()
+{
+  Registry_Key IE_key(HKEY_LOCAL_MACHINE, L"Software\\Microsoft\\Internet Explorer");
+  std::wstring version(IE_key.value_wstring(L"Version"));
+  /*
+   * We're expecting a version string that matches the regex "^[1-9]\.".
+   * Since IE versions 10 and 11 use a version string that begins with "9.", this simplistic parsing method works adequately.
+   */
+  if (version.length() < 2 || version[1] != '.' || version[0] < L'0' || version[0] > L'9')
+  {
+    throw std::runtime_error("IE version string has unexpected format");
+  }
+  if (version[0] != L'9')
+  {
+    return version;
+  }
+  // Assert the major version in the "Version" value is 9.
+  /*
+   * Version 9 might either be an actual version 9 or it might represent a version >= 10
+   * If the value named "svcVersion" exists, we'll report that instead.
+   */
+  try
+  {
+    version = IE_key.value_wstring(L"svcVersion"); // throws if value not found
+  }
+  catch (...)
+  {
+    // Assert svcVersion value not found
+    // Thus the major version is 9
+    return version;
+  } 
+  // Assert major version is >= 10
+  if (version.length() < 3 || version[0] < L'0' || version[0] > L'9' || version[1] < L'0' || version[1] > L'9' || version[2] != L'.')
+  {
+    throw std::runtime_error("IE version string has unexpected format");
+  }
+  return version;
+}
+
+std::wstring AdblockPlus::IE::InstalledVersionString()
+{
+  try
+  {
+    return IE_version_string();
+  }
+  catch (...)
+  {
+    return L"";
+  }
+}
+
+int AdblockPlus::IE::InstalledMajorVersion()
+{
+  try
+  {
+    std::wstring version = IE_version_string();
+    /*
+     * The version number is either one or two digits,
+     *   and thus either the second or third character is a period,
+     */
+    if (version[1] == L'.')
+    {
+      return version[0] - L'0';
+    } 
+    else if (version[2] == L'.')
+    {
+      return 10 * (version[0] - L'0') + (version[1] - L'0');
+    }
+  }
+  catch (...)
+  {
+  }
+  return 0;
+}