#include "cxxabi.h"

#include "unwind_env.h"

#include "unwinder.h"

#include "symbian_support.h"

// For information about these classes, se

// www.codesourcery.com/public/cxx-abi/abi.html#rtti. 

using abi::__class_type_info;

using abi::__si_class_type_info;

using abi::__vmi_class_type_info;

using abi::__base_class_type_info;

// Given base class info (aBaseInfo) and a derived object pointer (aDerivedObj),

// this function implements "cast to base" and stores result in aBaseObj. This

// essentially sets aBaseObj to point to a memory location that represents

// aDerivedObj as the given base class. This function requires that aBaseInfo

// describes a base class of the aDerivedObj's class.

static void _CastUp(const __base_class_type_info& aBaseInfo, TAny** aDerivedObj, TAny** aBaseObj)

	{

	// Guard against a null pointer for aDerivedObj

	if ( ! (*aDerivedObj) ) 

		{

		*aBaseObj = NULL;

		return;

		}

	TInt offset = aBaseInfo.__offset_flags >> aBaseInfo.__offset_shift;

	if (aBaseInfo.__offset_flags & aBaseInfo.__virtual_mask)

		{

		// For virtual bases, look up offset in vtable + offset.

		// Get vtbl pointer as the first 4 bytes of **aDerivedObj

		TUint32* vptr = (TUint32*) ( *( (TUint32*) (*aDerivedObj) ) );

		offset = *( vptr + offset / sizeof(TUint32) );

		}

	// Apply the offset.

	*aBaseObj = (TAny*) ( ( (TUint8*) *aDerivedObj ) + offset );

	}

// For a description of this function, see comments in unwind_env.h.

extern "C" TBool _DoDerivedToBaseConversion(const std::type_info* aDerivedType,

		                                    const std::type_info* aBaseType,

		                                    TAny**                aDerivedObj,

		                                    TAny**                aBaseObj)

	{

	const std::type_info& type_base_type = typeid(*aBaseType);

	const std::type_info& type_derived_type = typeid(*aDerivedType);

	// We must proceed depending on the type of the type_info objects for derived

	// class.  

	if ( type_derived_type == typeid(__si_class_type_info) )

		{

		// The __si_class_type_info means that the derived type has a single,

		// public, non-virtual base, and that the base is at offset zero. We should

		// be able to simply compare the base type from __si_class_type_info with

		// aBaseType

		const __si_class_type_info* derived = (const __si_class_type_info*) aDerivedType;

		if ( *(derived->__base_type) == *aBaseType ) 

			{

			// The types match, work done.

			*aBaseObj = *aDerivedObj;

			return true;

			} 

		else 

			{

			// The types don't match. We should proceed to comparison with the any

			// classes. In this case there is a single base as follows:

			const __class_type_info* bType = derived->__base_type;

			// No pointer adjustment required for __si_class_type_info. 

			return _DoDerivedToBaseConversion(bType, aBaseType, aDerivedObj, aBaseObj);

			}

		}

	else if ( type_derived_type == typeid(__vmi_class_type_info) ) 

		{

		// The __vmi_class_type_info is for all other scenarios. We get an array of

		// bases which we need to traverse and do comparison on.

		const __vmi_class_type_info* derived = (const __vmi_class_type_info*)aDerivedType;

		const unsigned count = derived->__base_count;

		for ( unsigned i = 0; i < count; i++ ) 

			{

			// Get the base info for this base class

			const __base_class_type_info bInfo = derived->__base_info[i];

			if ( ! ( bInfo.__offset_flags & bInfo.__public_mask) )

				{

				// The base is non-public base, so the remainder of the hierarchy

				// above this base is of no interest

				continue;

				} 

			// Get the class type info for this base

			const __class_type_info* bType = bInfo.__base_type;

			// First check if the type from the list corresponds to requested base

			// type.  

			if ( (*bType) == (*aBaseType) ) 

				{

				// Match! Convert the pointer to point to the base.

				_CastUp(bInfo, aDerivedObj, aBaseObj);

				return true;

				}

			// No match, we must now recursively delve into superclasses of bType.

			// To do that, we need to advance the derived class pointer to point to

			// the current base class as in bInfo.

			TAny* newDerivedPtr;

			_CastUp(bInfo, aDerivedObj, &newDerivedPtr);

			// Now go recursive, substituting aDerivedObj with adjusted pointer and bType instead of aDerivedType 

			TBool result = _DoDerivedToBaseConversion(bType, aBaseType, (TAny**)(&newDerivedPtr), aBaseObj);

			// Return only if the match is found, otherwise continue with the loop

			if ( result ) 

				{

				// Match came back from recursion, pass up.

				return true;

				}

			// No match from recursion, advance to next base.

			}

		}

	else

		{

		// assert(0);

		}

	// No match was found for aBaseType in the aDerivedType's ancestry.

	return false;

	}