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

src/shared/Utils.cpp

Index: src/shared/Utils.cpp
===================================================================
--- a/src/shared/Utils.cpp
+++ b/src/shared/Utils.cpp
@@ -128,3 +128,227 @@
     input.replace(replaceStart, placeholder.length(), replacement);
   }
 }
+
+namespace
+{

[Eric, 2014/06/21 20:45:36]

Registry_Key should be used to refactor use of the registry to manipulate the
status bar. It would need to support assignment (write to registry) in order to
do that.

That's a task for later.

+  /**
+   * An open key in the system registry.
+   */
+  class Registry_Key
+  {
+    /**
+     * Handle to an open registry key.
+     */
+    HKEY _key;

[Oleksandr, 2014/06/22 21:53:17]

Nit: Either m_key, as have in other parts of code, or just key without
underline, since we're not using Hungarian notation

[Eric, 2014/06/25 18:52:02]

Done.

+
+    /**
+     * Flag whether the registry key is predefined or not.
+     *
+     * Predefined key values are considered "always open" and should not be closed in the destructor.
+     */
+    bool _is_predefined;
+
+  public:
+    /**
+     * Enumeration for predefined root keys.
+     */
+    enum class Predefined
+      : unsigned int
+    {
+      HKCR = 0,   // HKEY_CLASSES_ROOT
+      HKCC,       // HKEY_CURRENT_CONFIG
+      HKCU,       // HKEY_CURRENT_USER
+      HKLM,       // HKEY_LOCAL_MACHINE
+      HKU         // HKEY_USERS
+    };
+
+    /**
+     * Constructor to open a key starting an one of the predefined roots.
+     * Opens the key with read-only access.
+     */
+    Registry_Key( Predefined root, std::wstring key_name );

[Oleksandr, 2014/06/22 21:53:17]

Nit: no spaces after and before the parentheses here and further in this file

+
+    /**
+     * Destructor closes the key if it's not a predefined one.
+     */
+    ~Registry_Key();
+
+    /**
+     * Retrieve a value from a name-value pair within the present key.
+     *
+     * Throws if the name is not found within the dictionary.
+     * Throws if the name is found but is not a string.
+     */
+    std::wstring value_wstring( std::wstring name ) const;
+
+  private:
+    /**
+     */
+    inline HKEY hkey_of_prefined( Predefined root )

[Oleksandr, 2014/06/22 21:53:17]

I guess should've been hkey_of_predefined?

[Eric, 2014/06/25 18:52:02]

Yes. Derp.

Done.

+    {
+      static HKEY predefined_hkeys[ 5 ] = 

[Oleksandr, 2014/06/22 21:53:17]

Nit: no spaces before and after brackets here and further in this file

[Oleksandr, 2014/07/15 18:25:11]

It's fixed here, but not everywhere else :)
On 2014/06/22 21:53:17, Oleksandr wrote:

+      {
+        HKEY_CLASSES_ROOT,
+        HKEY_CURRENT_CONFIG,
+        HKEY_CURRENT_USER,
+        HKEY_LOCAL_MACHINE,
+        HKEY_USERS
+      };
+      return predefined_hkeys[ (unsigned int) root ];
+    }
+
+  };
+
+  Registry_Key::Registry_Key( Predefined root, std::wstring key_name )
+    : _is_predefined( key_name.empty() )
+  {
+    HRESULT hr = RegOpenKeyExW( hkey_of_prefined( root ), key_name.c_str(), 0, KEY_QUERY_VALUE, &_key );
+    if ( hr != ERROR_SUCCESS || !_key )
+    {
+      throw std::runtime_error( "Failure in RegOpenKeyExW" );
+    }
+  }
+
+  Registry_Key::~Registry_Key()
+  {
+    if ( ! _is_predefined )
+    {
+      RegCloseKey( _key );
+    }
+  }
+
+  std::wstring Registry_Key::value_wstring( std::wstring name ) const
+  {
+    /*
+     * Step one is to determine the presence of the value, along with its type and byte size. 
+     */
+    DWORD type;
+    DWORD size = 0;
+    HRESULT hr = ::RegQueryValueExW( _key, name.c_str(), 0, &type, 0, &size );
+    if ( hr != ERROR_SUCCESS )
+    {
+      throw std::runtime_error( "Failure in RegQueryValueEx to query name" );
+    }
+    if ( type != REG_SZ )
+    {
+      throw std::runtime_error( "Value is not string type" );
+    }
+
+    /*
+     * Step two is to allocate a buffer for the string and query for its value.
+     * Note that 'size' is the size in bytes, which we need for the system call,
+     *   but that 'psize' is the size in words, which we need to manipulate the wchar_t array 'p'.
+     */
+    // Round the byte size up to the nearest multiple of two.
+    size = ( size + 1 ) & ~ DWORD(1);
+    size_t psize = size >> 1;
+    // We need to allocate a temporary buffer to receive the value, because there's no interface to write directly into the buffer of std::basic_string.
+    std::unique_ptr< wchar_t[] > p( new wchar_t[ psize ] );
+    hr = RegQueryValueExW( _key, name.c_str(), 0, 0, reinterpret_cast<BYTE *>( p.get() ), &size );
+    if ( hr != ERROR_SUCCESS )
+    {
+      throw std::runtime_error( "Failure in RegQueryValueExW to retrieve value" );
+    }
+
+    /*
+     * Step three is to construct a return string.
+     *
+     * There's the possibility of an extra terminating null character in the return value of the query.
+     * If so, we have to decrement the length of the return value to eliminate it.
+     * If it persists, it will interfere with later string operations such as concatenation.
+     */
+    if ( p[ psize - 1 ] == L'\0' )
+    {
+      --psize;
+    }
+    return std::wstring( p.get(), psize );  
+  }
+
+  /**
+   * 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
+   */
+
+  std::wstring IE_version_string()
+  {
+    Registry_Key IE_key( Registry_Key::Predefined::HKLM, 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.
+     * Warning: IE version 12 and later might not behave the same, so this function should be reviewed with each new release.
+     */
+    if ( version[1] != '.' || version[0] < L'0' || version[0] > L'9' )
+    {
+      throw std::runtime_error( "IE version string has unexpected format" );

[Wladimir Palant, 2014/06/23 06:54:49]

So, we crash and burn if the we see an unexpected version format? I don't think
the callers are handling this exception, meaning that it will actually terminate
the application. If catching this exception in the callers is too complicated,
maybe we should just return some default value like 0 or -1 here?

[Eric, 2014/06/25 18:52:02]

IE_version_string() is only called (at present) by the two functions immediately
below, which do exactly as you suggest, returning default values of L"" and 0
respectively if they catch an exception.

+    }
+    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
+    {
+      return IE_key.value_wstring( L"svcVersion" );
+    }
+    catch ( ... )
+    {
+      return version;
+    }
+  }
+}
+
+
+std::wstring ABP::IE::installed_version_string()
+{
+  try
+  {
+    return IE_version_string();
+  }
+  catch ( ... )
+  {
+    return L"";
+  }
+}
+
+int ABP::IE::installed_major_version()
+{
+  try
+  {
+    std::wstring version = IE_version_string();
+    /*
+     * If the second character is a period, we assume that the major version is a single digit.
+     */
+    if ( version[ 1 ] == L'.' )
+    {
+      return version[ 0 ] - L'0';
+    }
+    // Assert IE_version_string() did not verify the syntax of the version string.
+    /*
+     * In this case, we'll assume that the version returned is two digits followed by a period.
+     * If not, we'll assume an error.
+     */
+    if ( version[ 0 ] < L'0' || version[ 0 ] > L'9' || version[ 1 ] < L'0' || version[ 1 ] > L'9' || version[ 2 ] != L'.' )
+    {
+      return 0;
+    }
+    return 10 * ( version[ 0 ] - L'0' ) + ( version[ 1 ] - L'0' );
+  }
+  catch ( ... )
+  {
+    return 0;
+  }
+}
+
+