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

src/shared/Registry.cpp

Index: src/shared/Registry.cpp
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/shared/Registry.cpp
@@ -0,0 +1,91 @@
+#include "Registry.h"
+#include <memory>
+
+using namespace AdblockPlus;
+
+static HKEY predefined_hkeys[5] = 
+{
+  HKEY_CLASSES_ROOT,
+  HKEY_CURRENT_CONFIG,
+  HKEY_CURRENT_USER,
+  HKEY_LOCAL_MACHINE,
+  HKEY_USERS
+};
+
+Registry_Key::Registry_Key( Predefined root, std::wstring key_name )

[Oleksandr, 2014/07/25 22:23:46]

Formatting in this file is too spacious as well

+  : is_predefined( key_name.empty() )
+{
+  auto predefined_key( predefined_hkeys[ (unsigned int) root ] );
+  if ( is_predefined )
+  {
+    key = predefined_key;
+    return;
+  }
+  HRESULT hr = RegOpenKeyExW( predefined_key, 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( Predefined root )
+  : key( predefined_hkeys[ (unsigned int) root ] ), is_predefined( true )
+{
+}
+
+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( static_cast<HKEY>( 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 );  
+}
+
+