/// <summary>
/// Interprets a pointer within the current segment as capability pointer and returns the according low-level capability object from
/// the capability table. Does not mutate this state.
/// </summary>
/// <param name="offset">Offset relative to this.Offset within current segment</param>
/// <returns>the low-level capability object</returns>
/// <exception cref="IndexOutOfRangeException">offset negative or out of range</exception>
/// <exception cref="InvalidOperationException">capability table not set</exception>
/// <exception cref="Rpc.RpcException">not a capability pointer or invalid capability index</exception>
internal Rpc.ConsumedCapability DecodeCapPointer(int offset)
{
if (offset < 0)
{
throw new IndexOutOfRangeException(nameof(offset));
}
if (Caps == null)
{
throw new InvalidOperationException("Capbility table not set");
}
WirePointer pointer = CurrentSegment[Offset + offset];
if (pointer.IsNull)
{
// Despite this behavior is not officially specified,
// the official C++ implementation seems to send null pointers for null caps.
return(null);
}
if (pointer.Kind != PointerKind.Other)
{
throw new Rpc.RpcException("Expected a capability pointer, but got something different");
}
if (pointer.CapabilityIndex >= Caps.Count)
{
throw new Rpc.RpcException("Capability index out of range");
}
return(Caps[(int)pointer.CapabilityIndex]);
}
/// <summary>
/// Interprets a pointer within the current segment and mutates this state to represent the pointer's target.
/// </summary>
/// <param name="offset">word offset relative to this.Offset within current segment</param>
/// <exception cref="IndexOutOfRangeException">offset negative or out of range</exception>
/// <exception cref="DeserializationException">invalid pointer data or traversal limit exceeded</exception>
internal void DecodePointer(int offset)
{
if (offset < 0)
{
throw new IndexOutOfRangeException(nameof(offset));
}
WirePointer pointer = CurrentSegment[Offset + offset];
int derefCount = 0;
do
{
if (pointer.IsNull)
{
this = default;
return;
}
switch (pointer.Kind)
{
case PointerKind.Struct:
Offset = checked (pointer.Offset + Offset + offset + 1);
IncrementBytesTraversed(checked (8u * pointer.StructSize));
StructDataCount = pointer.StructDataCount;
StructPtrCount = pointer.StructPtrCount;
Kind = ObjectKind.Struct;
Validate();
return;
case PointerKind.List:
Offset = checked (pointer.Offset + Offset + offset + 1);
ListElementCount = pointer.ListElementCount;
StructDataCount = 0;
StructPtrCount = 0;
switch (pointer.ListKind)
{
case ListKind.ListOfEmpty: // e.g. List(void)
// the “traversal limit” should count a list of zero-sized elements as if each element were one word instead.
IncrementBytesTraversed(checked (8u * (uint)ListElementCount));
Kind = ObjectKind.ListOfEmpty;
break;
case ListKind.ListOfBits:
IncrementBytesTraversed(checked ((uint)ListElementCount + 7) / 8);
Kind = ObjectKind.ListOfBits;
break;
case ListKind.ListOfBytes:
IncrementBytesTraversed((uint)ListElementCount);
Kind = ObjectKind.ListOfBytes;
break;
case ListKind.ListOfShorts:
IncrementBytesTraversed(checked (2u * (uint)ListElementCount));
Kind = ObjectKind.ListOfShorts;
break;
case ListKind.ListOfInts:
IncrementBytesTraversed(checked (4u * (uint)ListElementCount));
Kind = ObjectKind.ListOfInts;
break;
case ListKind.ListOfLongs:
IncrementBytesTraversed(checked (8u * (uint)ListElementCount));
Kind = ObjectKind.ListOfLongs;
break;
case ListKind.ListOfPointers:
IncrementBytesTraversed(checked (8u * (uint)ListElementCount));
Kind = ObjectKind.ListOfPointers;
break;
case ListKind.ListOfStructs:
{
WirePointer tag = CurrentSegment[Offset];
if (tag.Kind != PointerKind.Struct)
{
throw new DeserializationException("Unexpected: List of composites with non-struct type tag");
}
IncrementBytesTraversed(checked (8u * (uint)pointer.ListElementCount + 8u));
ListElementCount = tag.ListOfStructsElementCount;
StructDataCount = tag.StructDataCount;
StructPtrCount = tag.StructPtrCount;
Kind = ObjectKind.ListOfStructs;
}
break;
default:
throw new InvalidProgramException();
}
Validate();
return;
case PointerKind.Far:
if (pointer.IsDoubleFar)
{
CurrentSegmentIndex = pointer.TargetSegmentIndex;
Offset = 0;
WirePointer pointer1 = CurrentSegment[pointer.LandingPadOffset];
if (pointer1.Kind != PointerKind.Far || pointer1.IsDoubleFar)
{
throw new DeserializationException("Error decoding double-far pointer: convention broken");
}
WirePointer pointer2 = CurrentSegment[pointer.LandingPadOffset + 1];
if (pointer2.Kind == PointerKind.Far)
{
throw new DeserializationException("Error decoding double-far pointer: not followed by intra-segment pointer");
}
CurrentSegmentIndex = pointer1.TargetSegmentIndex;
Offset = 0;
pointer = pointer2;
offset = -1;
}
else
{
CurrentSegmentIndex = pointer.TargetSegmentIndex;
Offset = 0;
offset = pointer.LandingPadOffset;
pointer = CurrentSegment[pointer.LandingPadOffset];
}
continue;
case PointerKind.Other:
var tmp = Caps;
this = default;
Caps = tmp;
Kind = ObjectKind.Capability;
BytesTraversedOrData = pointer.CapabilityIndex;
return;
default:
throw new InvalidProgramException();
}
} while (++derefCount < SecurityOptions.RecursionLimit);
throw new DeserializationException("Recursion limit reached while decoding a pointer");
}
