sl@0: // Copyright (c) 2004-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of the License "ARM EABI LICENCE.txt"
sl@0: // which accompanies this distribution, and is available
sl@0: // in kernel/eka/compsupp.
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: // e32/compsupp/symaehabi/symbian_rtti.cpp
sl@0: // 
sl@0: //
sl@0: 
sl@0: #include "cxxabi.h"
sl@0: #include "unwind_env.h"
sl@0: #include "unwinder.h"
sl@0: #include "symbian_support.h"
sl@0: 
sl@0: // For information about these classes, se
sl@0: // www.codesourcery.com/public/cxx-abi/abi.html#rtti. 
sl@0: using abi::__class_type_info;
sl@0: using abi::__si_class_type_info;
sl@0: using abi::__vmi_class_type_info;
sl@0: using abi::__base_class_type_info;
sl@0: 
sl@0: 
sl@0: // Given base class info (aBaseInfo) and a derived object pointer (aDerivedObj),
sl@0: // this function implements "cast to base" and stores result in aBaseObj. This
sl@0: // essentially sets aBaseObj to point to a memory location that represents
sl@0: // aDerivedObj as the given base class. This function requires that aBaseInfo
sl@0: // describes a base class of the aDerivedObj's class.
sl@0: static void _CastUp(const __base_class_type_info& aBaseInfo, TAny** aDerivedObj, TAny** aBaseObj)
sl@0: 	{
sl@0: 	// Guard against a null pointer for aDerivedObj
sl@0: 	if ( ! (*aDerivedObj) ) 
sl@0: 		{
sl@0: 		*aBaseObj = NULL;
sl@0: 		return;
sl@0: 		}
sl@0: 
sl@0: 	TInt offset = aBaseInfo.__offset_flags >> aBaseInfo.__offset_shift;
sl@0: 
sl@0: 	if (aBaseInfo.__offset_flags & aBaseInfo.__virtual_mask)
sl@0: 		{
sl@0: 		// For virtual bases, look up offset in vtable + offset.
sl@0: 
sl@0: 		// Get vtbl pointer as the first 4 bytes of **aDerivedObj
sl@0: 		TUint32* vptr = (TUint32*) ( *( (TUint32*) (*aDerivedObj) ) );
sl@0: 
sl@0: 		offset = *( vptr + offset / sizeof(TUint32) );
sl@0: 		}
sl@0: 
sl@0: 	// Apply the offset.
sl@0: 	*aBaseObj = (TAny*) ( ( (TUint8*) *aDerivedObj ) + offset );
sl@0: 	}
sl@0: 
sl@0: 
sl@0: // For a description of this function, see comments in unwind_env.h.
sl@0: extern "C" TBool _DoDerivedToBaseConversion(const std::type_info* aDerivedType,
sl@0: 		                                    const std::type_info* aBaseType,
sl@0: 		                                    TAny**                aDerivedObj,
sl@0: 		                                    TAny**                aBaseObj)
sl@0: 	{
sl@0: 
sl@0: 	const std::type_info& type_base_type = typeid(*aBaseType);
sl@0: 	const std::type_info& type_derived_type = typeid(*aDerivedType);
sl@0: 
sl@0: 	// We must proceed depending on the type of the type_info objects for derived
sl@0: 	// class.  
sl@0: 	if ( type_derived_type == typeid(__si_class_type_info) )
sl@0: 		{
sl@0: 		// The __si_class_type_info means that the derived type has a single,
sl@0: 		// public, non-virtual base, and that the base is at offset zero. We should
sl@0: 		// be able to simply compare the base type from __si_class_type_info with
sl@0: 		// aBaseType
sl@0: 
sl@0: 		const __si_class_type_info* derived = (const __si_class_type_info*) aDerivedType;
sl@0: 
sl@0: 		if ( *(derived->__base_type) == *aBaseType ) 
sl@0: 			{
sl@0: 			// The types match, work done.
sl@0: 			*aBaseObj = *aDerivedObj;
sl@0: 			return true;
sl@0: 			} 
sl@0: 		else 
sl@0: 			{
sl@0: 			// The types don't match. We should proceed to comparison with the any
sl@0: 			// classes. In this case there is a single base as follows:
sl@0: 			const __class_type_info* bType = derived->__base_type;
sl@0: 
sl@0: 			// No pointer adjustment required for __si_class_type_info. 
sl@0: 			return _DoDerivedToBaseConversion(bType, aBaseType, aDerivedObj, aBaseObj);
sl@0: 			}
sl@0: 		}
sl@0: 	else if ( type_derived_type == typeid(__vmi_class_type_info) ) 
sl@0: 		{
sl@0: 		// The __vmi_class_type_info is for all other scenarios. We get an array of
sl@0: 		// bases which we need to traverse and do comparison on.
sl@0: 
sl@0: 		const __vmi_class_type_info* derived = (const __vmi_class_type_info*)aDerivedType;
sl@0: 
sl@0: 		const unsigned count = derived->__base_count;
sl@0: 
sl@0: 		for ( unsigned i = 0; i < count; i++ ) 
sl@0: 			{
sl@0: 			// Get the base info for this base class
sl@0: 			const __base_class_type_info bInfo = derived->__base_info[i];
sl@0: 
sl@0: 			if ( ! ( bInfo.__offset_flags & bInfo.__public_mask) )
sl@0: 				{
sl@0: 				// The base is non-public base, so the remainder of the hierarchy
sl@0: 				// above this base is of no interest
sl@0: 				continue;
sl@0: 				} 
sl@0: 
sl@0: 			// Get the class type info for this base
sl@0: 			const __class_type_info* bType = bInfo.__base_type;
sl@0: 
sl@0: 			// First check if the type from the list corresponds to requested base
sl@0: 			// type.  
sl@0: 			if ( (*bType) == (*aBaseType) ) 
sl@0: 				{
sl@0: 				// Match! Convert the pointer to point to the base.
sl@0: 				_CastUp(bInfo, aDerivedObj, aBaseObj);
sl@0: 				return true;
sl@0: 				}
sl@0: 
sl@0: 			// No match, we must now recursively delve into superclasses of bType.
sl@0: 			// To do that, we need to advance the derived class pointer to point to
sl@0: 			// the current base class as in bInfo.
sl@0: 			TAny* newDerivedPtr;
sl@0: 			_CastUp(bInfo, aDerivedObj, &newDerivedPtr);
sl@0: 
sl@0: 			// Now go recursive, substituting aDerivedObj with adjusted pointer and bType instead of aDerivedType 
sl@0: 			TBool result = _DoDerivedToBaseConversion(bType, aBaseType, (TAny**)(&newDerivedPtr), aBaseObj);
sl@0: 
sl@0: 			// Return only if the match is found, otherwise continue with the loop
sl@0: 			if ( result ) 
sl@0: 				{
sl@0: 				// Match came back from recursion, pass up.
sl@0: 				return true;
sl@0: 				}
sl@0: 
sl@0: 			// No match from recursion, advance to next base.
sl@0: 			}
sl@0: 		}
sl@0: 	else
sl@0: 		{
sl@0: 		// assert(0);
sl@0: 		}
sl@0: 
sl@0: 	// No match was found for aBaseType in the aDerivedType's ancestry.
sl@0: 	return false;
sl@0: 	}
sl@0: