protected override RuntimeInterfacesAlgorithm GetRuntimeInterfacesAlgorithmForDefType(DefType type)
{
if (type.RetrieveRuntimeTypeHandleIfPossible() && !type.IsGenericDefinition)
{
// If the type is already constructed, use the NoMetadataRuntimeInterfacesAlgorithm.
// its more efficient than loading from native layout or metadata.
return s_noMetadataRuntimeInterfacesAlgorithm;
}
else if (type.HasNativeLayout)
{
return s_nativeLayoutInterfacesAlgorithm;
}
else if (type is NoMetadataType)
{
return s_noMetadataRuntimeInterfacesAlgorithm;
}
else if (type is MetadataType)
{
return s_metadataRuntimeInterfacesAlgorithm;
}
else
{
Debug.Assert(false);
return null;
}
}
public unsafe override bool ComputeContainsGCPointers(DefType type)
{
if (type.IsTemplateCanonical())
{
return type.ComputeTemplate().RuntimeTypeHandle.ToEETypePtr()->HasGCPointers;
}
else
{
if (type.RetrieveRuntimeTypeHandleIfPossible())
{
return type.RuntimeTypeHandle.ToEETypePtr()->HasGCPointers;
}
return type.GetOrCreateTypeBuilderState().InstanceGCLayout != null;
}
}
public override FieldLayoutAlgorithm GetLayoutAlgorithmForType(DefType type)
{
if (type.RetrieveRuntimeTypeHandleIfPossible())
{
// If the type is already constructed, use the NoMetadataFieldLayoutAlgorithm.
// its more efficient than loading from native layout or metadata.
return s_noMetadataFieldLayoutAlgorithm;
}
if (type.HasNativeLayout)
{
return s_nativeLayoutFieldAlgorithm;
}
else if (type is NoMetadataType)
{
return s_noMetadataFieldLayoutAlgorithm;
}
else
{
return s_metadataFieldLayoutAlgorithm;
}
}
/// <summary>
/// Given a type, and vtable slot index, compute either the NativeFormatMethod that defines that vtable slot,
/// OR the implementation function pointer if the method doesn't have sufficient metadata to be interesting
/// to use the virtual function resolution algorithm on.
/// </summary>
/// <param name="type">Type on which virtual resolution is to be completed</param>
/// <param name="vtableSlotIndex">Virtual slot index which is to be examined</param>
/// <param name="functionPointer">If there is no corresponding method defined in metadata, this is
/// the function pointer that should be used for calls to this vtable slot</param>
/// <returns>MethodDesc of function that defined the slot if possible.</returns>
private unsafe static MethodDesc ResolveVTableSlotIndexToMethodDescOrFunctionPointer(DefType type, int vtableSlotIndex, out IntPtr functionPointer)
{
Debug.Assert(type.RetrieveRuntimeTypeHandleIfPossible());
Debug.Assert(type.RuntimeTypeHandle.ToEETypePtr()->NumVtableSlots > vtableSlotIndex);
DefType definingTypeScan = type;
DefType previousDefiningType = null;
EEType* typePtr = null;
DefType definingType = null;
functionPointer = IntPtr.Zero;
while (true)
{
definingTypeScan.RetrieveRuntimeTypeHandleIfPossible();
Debug.Assert(!definingTypeScan.RuntimeTypeHandle.IsNull());
typePtr = definingTypeScan.RuntimeTypeHandle.ToEETypePtr();
if (typePtr->NumVtableSlots > vtableSlotIndex)
{
previousDefiningType = definingTypeScan;
definingTypeScan = definingTypeScan.BaseType;
// We found a slot on System.Object
if (definingTypeScan == null)
{
definingType = previousDefiningType;
break;
}
}
else
{
// We've gone past the type in the type hierarchy that declared this vtable slot
// the defining type is the one we looked at previously
definingType = previousDefiningType;
break;
}
}
// At this point, we know the type that definined the virtual slot
// There are 4 possibilities here
// 1. The definingType is a R2R type with full metadata. Compute the MethodDesc, by scanning the list of virtuals present in metadata
// 2. The definingType is pregenerated, but we can go from the slot index to metadata via the runtime mapping tables. Do so, then run
// normal algorithm
// 3. The definingType is pregenerated, but we cannot go from the slot index to metadata via the runtime mapping tables. There is
// only 1 pointer in the vtable of the most derived pregenerated type that has the same value. That's the valuable pointer.
// 4. The definingType is pregenerated, but we cannot go from the slot index to metadata via the runtime mapping tables. There are
// multiple pointers in the vtable of the most derived pregenerated types which have this same value.
// - Take that pointer value, and attempt to resolve back to a method from the implementation. If that succeeds, then
// treat that as the correct vtable slot. Otherwise, return that function pointer. (This is a very rare scenario.)
MethodDesc slotDefiningMethod = null;
if (!IsPregeneratedOrTemplateTypeLoaded(definingType))
{
// Case 1
MetadataType definingMetadataType = (MetadataType)definingType;
int baseTypeSlotCount = 0;
if (definingMetadataType.BaseType != null)
baseTypeSlotCount = definingMetadataType.BaseType.GetRuntimeTypeHandle().ToEETypePtr()->NumVtableSlots;
int slotOnType = vtableSlotIndex - baseTypeSlotCount;
Debug.Assert(slotOnType >= 0);
// R2R types create new slots only for methods that are marked as NewSlot
if (definingMetadataType.ConvertToCanonForm(CanonicalFormKind.Specific) != definingType)
{
// Deal with the space reserved for the canonical dictionary
slotOnType--;
}
Debug.Assert(slotOnType >= 0);
int currentSlot = 0;
foreach (MethodDesc method in definingMetadataType.GetMethods())
{
if (!MethodDefinesVTableSlot(method))
continue;
if (currentSlot == slotOnType)
{
Debug.Assert(VirtualMethodToSlotIndex(method) == vtableSlotIndex);
return method;
}
else
currentSlot++;
}
Environment.FailFast("Unexpected failure to find virtual function that defined slot");
return null;
}
else if (TryGetVirtualMethodFromSlot(definingType, vtableSlotIndex, out slotDefiningMethod))
{
// Case 2
Debug.Assert(VirtualMethodToSlotIndex(slotDefiningMethod) == vtableSlotIndex);
return slotDefiningMethod;
}
else
{
TypeDesc mostDerivedPregeneratedType = GetMostDerivedPregeneratedOrTemplateLoadedType(type);
EEType* mostDerivedTypeEEType = mostDerivedPregeneratedType.GetRuntimeTypeHandle().ToEETypePtr();
IntPtr* vtableStart = (IntPtr*)(((byte*)mostDerivedTypeEEType) + sizeof(EEType));
IntPtr possibleFunctionPointerReturn = vtableStart[vtableSlotIndex];
int functionPointerMatches = 0;
for (int i = 0; i < mostDerivedTypeEEType->NumVtableSlots; i++)
{
if (vtableStart[i] == possibleFunctionPointerReturn)
functionPointerMatches++;
}
if (functionPointerMatches == 1)
{
// Case 3
functionPointer = possibleFunctionPointerReturn;
return null;
}
else
{
// Case 4
// While this case is theoretically possible, it requires MethodImpl to MethodImpl overloading for virtual functions
// in the non-ready to run portions of the binary. Given our current shipping plans, as this does not occur in non-obfuscated
// code, we will throw NotImplementedException here.
// The real implementation would look something like
// if (!TryGetNativeFormatMethodFromFunctionPointer(possibleFunctionPointerReturn, out method))
// {
// // this method could not have been overriden in dynamically loaded code
// functionPointer = possibleFunctionPointerReturn;
// return null;
// }
// else
// {
// return VirtualFunctionAlgorithm.GetDefiningMethod(method)
// }
//
throw NotImplemented.ByDesign;
}
}
}