Issues #276, #1163 - introduce class IncomingParam

src/plugin/COM_Value.cpp

 /**
  * \file COM_Value.cpp Support for the values used in COM and Automation.
  */
 #include "COM_Value.h"
 #include <stdexcept>
 
 using namespace AdblockPlus::COM;
 
 /*
  * MSDN SysAllocStringLen function http://msdn.microsoft.com/en-us/library/windows/desktop/ms221639%28v=vs.85%29.aspx
  */
-BSTR_Argument::BSTR_Argument( const std::wstring& s )
+BSTR_Argument::BSTR_Argument(const std::wstring& s)
 {
   auto length = s.length();
-  if ( length == 0 )
+  if (length == 0)
   {
     /*
      * BSTR makes no distinction between null pointers and non-null pointers to the empty string.
      * In order to detect allocation failure reliably, we simply don't allocate empty strings.
      * Compare with the default constructor.
      */
     bstr = nullptr;
     return;
   }
   // Assert length >= 1
-  bstr = SysAllocStringLen( s.c_str(), length );
+  bstr = SysAllocStringLen(s.c_str(), length);
   /*
    * Since the string is non-empty,
    *   if the return value of SysAllocStringLen is null it means that it had an allocation failure.
    */
-  if ( !bstr )
+  if (!bstr)
   {
     throw std::bad_alloc();
   }
 }
 
 /*
  * MSDN SysFreeString function http://msdn.microsoft.com/en-us/library/windows/desktop/ms221481%28v=vs.85%29.aspx
  */
 BSTR_Argument::~BSTR_Argument()
 {
   // There's no need to check for null; SysFreeString already handles that case.
-  SysFreeString( bstr );
+  SysFreeString(bstr);
 }
 
 BSTR* BSTR_Argument::operator&()
 {
   // Assign the empty string, if not already empty.
-  if ( bstr )
+  if (bstr)
   {
-    SysFreeString( bstr );
+    SysFreeString(bstr);
     bstr = nullptr;
   }
   return &bstr;
 }
 
 BSTR_Argument::operator std::wstring() const
 {
-  if ( !bstr )
+  if (!bstr)
   {
     return std::wstring();
   }
-  return std::wstring( bstr, SysStringLen( bstr ) );
+  return std::wstring(bstr, SysStringLen(bstr));
 }
 
 
-namespace
+bool IncomingParam::wstringConvertible() const
 {
-  /**
-   * Pre-construction assistant for wstring_Incoming_Param.
-   *
-   * Because wstring_Incoming_Param is a derived class,
-   *   we need to have a wstring value to initialize the base class.
+  /*
+   * Initial support is for BSTR only.
+   * We've got one case later where we'll need to support VT_I4.
    */
-  std::wstring construct_Incoming_Param( BSTR b )
-  {
-    if ( !b )
-    {
-      return std::wstring();
-    }
-    return std::wstring( b, SysStringLen( b ) );
-  }
+  return var.vt == VT_BSTR;
 }
 
-Incoming_Param::Incoming_Param( BSTR b )
-  : std::wstring( construct_Incoming_Param( b ) )
+std::wstring IncomingParam::wstringValueNoexcept() const
 {
+  return L"";
 }