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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Diagnostics;
using System.Runtime.InteropServices;
namespace System.Runtime.CompilerServices
{
[StackTraceHidden]
[DebuggerStepThrough]
internal static unsafe class CastHelpers
{
// In coreclr the table is allocated and written to on the native side.
internal static int[]? s_table;
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern object IsInstanceOfAny_NoCacheLookup(void* toTypeHnd, object obj);
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern object ChkCastAny_NoCacheLookup(void* toTypeHnd, object obj);
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern ref byte Unbox_Helper(void* toTypeHnd, object obj);
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern void WriteBarrier(ref object? dst, object? obj);
// IsInstanceOf test used for unusual cases (naked type parameters, variant generic types)
// Unlike the IsInstanceOfInterface and IsInstanceOfClass functions,
// this test must deal with all kinds of type tests
[DebuggerHidden]
private static object? IsInstanceOfAny(void* toTypeHnd, object? obj)
{
if (obj != null)
{
void* mt = RuntimeHelpers.GetMethodTable(obj);
if (mt != toTypeHnd)
{
CastResult result = CastCache.TryGet(s_table!, (nuint)mt, (nuint)toTypeHnd);
if (result == CastResult.CanCast)
{
// do nothing
}
else if (result == CastResult.CannotCast)
{
obj = null;
}
else
{
goto slowPath;
}
}
}
return obj;
slowPath:
// fall through to the slow helper
return IsInstanceOfAny_NoCacheLookup(toTypeHnd, obj);
}
[DebuggerHidden]
private static object? IsInstanceOfInterface(void* toTypeHnd, object? obj)
{
const int unrollSize = 4;
if (obj != null)
{
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj);
nint interfaceCount = mt->InterfaceCount;
if (interfaceCount != 0)
{
MethodTable** interfaceMap = mt->InterfaceMap;
if (interfaceCount < unrollSize)
{
// If not enough for unrolled, jmp straight to small loop
// as we already know there is one or more interfaces so don't need to check again.
goto few;
}
do
{
if (interfaceMap[0] == toTypeHnd ||
interfaceMap[1] == toTypeHnd ||
interfaceMap[2] == toTypeHnd ||
interfaceMap[3] == toTypeHnd)
{
goto done;
}
interfaceMap += unrollSize;
interfaceCount -= unrollSize;
} while (interfaceCount >= unrollSize);
if (interfaceCount == 0)
{
// If none remaining, skip the short loop
goto extra;
}
few:
do
{
if (interfaceMap[0] == toTypeHnd)
{
goto done;
}
// Assign next offset
interfaceMap++;
interfaceCount--;
} while (interfaceCount > 0);
}
extra:
if (mt->NonTrivialInterfaceCast)
{
goto slowPath;
}
obj = null;
}
done:
return obj;
slowPath:
return IsInstance_Helper(toTypeHnd, obj);
}
[DebuggerHidden]
private static object? IsInstanceOfClass(void* toTypeHnd, object? obj)
{
if (obj == null || RuntimeHelpers.GetMethodTable(obj) == toTypeHnd)
return obj;
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj)->ParentMethodTable;
for (; ; )
{
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
}
// this helper is not supposed to be used with type-equivalent "to" type.
Debug.Assert(!((MethodTable*)toTypeHnd)->HasTypeEquivalence);
obj = null;
done:
return obj;
}
[DebuggerHidden]
[MethodImpl(MethodImplOptions.NoInlining)]
private static object? IsInstance_Helper(void* toTypeHnd, object obj)
{
CastResult result = CastCache.TryGet(s_table!, (nuint)RuntimeHelpers.GetMethodTable(obj), (nuint)toTypeHnd);
if (result == CastResult.CanCast)
{
return obj;
}
else if (result == CastResult.CannotCast)
{
return null;
}
// fall through to the slow helper
return IsInstanceOfAny_NoCacheLookup(toTypeHnd, obj);
}
// ChkCast test used for unusual cases (naked type parameters, variant generic types)
// Unlike the ChkCastInterface and ChkCastClass functions,
// this test must deal with all kinds of type tests
[DebuggerHidden]
internal static object? ChkCastAny(void* toTypeHnd, object? obj)
{
CastResult result;
if (obj != null)
{
void* mt = RuntimeHelpers.GetMethodTable(obj);
if (mt != toTypeHnd)
{
result = CastCache.TryGet(s_table!, (nuint)mt, (nuint)toTypeHnd);
if (result != CastResult.CanCast)
{
goto slowPath;
}
}
}
return obj;
slowPath:
// fall through to the slow helper
object objRet = ChkCastAny_NoCacheLookup(toTypeHnd, obj);
// Make sure that the fast helper have not lied
Debug.Assert(result != CastResult.CannotCast);
return objRet;
}
[DebuggerHidden]
[MethodImpl(MethodImplOptions.NoInlining)]
private static object? ChkCast_Helper(void* toTypeHnd, object obj)
{
CastResult result = CastCache.TryGet(s_table!, (nuint)RuntimeHelpers.GetMethodTable(obj), (nuint)toTypeHnd);
if (result == CastResult.CanCast)
{
return obj;
}
// fall through to the slow helper
return ChkCastAny_NoCacheLookup(toTypeHnd, obj);
}
[DebuggerHidden]
private static object? ChkCastInterface(void* toTypeHnd, object? obj)
{
const int unrollSize = 4;
if (obj != null)
{
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj);
nint interfaceCount = mt->InterfaceCount;
if (interfaceCount == 0)
{
goto slowPath;
}
MethodTable** interfaceMap = mt->InterfaceMap;
if (interfaceCount < unrollSize)
{
// If not enough for unrolled, jmp straight to small loop
// as we already know there is one or more interfaces so don't need to check again.
goto few;
}
do
{
if (interfaceMap[0] == toTypeHnd ||
interfaceMap[1] == toTypeHnd ||
interfaceMap[2] == toTypeHnd ||
interfaceMap[3] == toTypeHnd)
{
goto done;
}
// Assign next offset
interfaceMap += unrollSize;
interfaceCount -= unrollSize;
} while (interfaceCount >= unrollSize);
if (interfaceCount == 0)
{
// If none remaining, skip the short loop
goto slowPath;
}
few:
do
{
if (interfaceMap[0] == toTypeHnd)
{
goto done;
}
// Assign next offset
interfaceMap++;
interfaceCount--;
} while (interfaceCount > 0);
goto slowPath;
}
done:
return obj;
slowPath:
return ChkCast_Helper(toTypeHnd, obj);
}
[DebuggerHidden]
private static object? ChkCastClass(void* toTypeHnd, object? obj)
{
if (obj == null || RuntimeHelpers.GetMethodTable(obj) == toTypeHnd)
{
return obj;
}
return ChkCastClassSpecial(toTypeHnd, obj);
}
// Optimized helper for classes. Assumes that the trivial cases
// has been taken care of by the inlined check
[DebuggerHidden]
private static object? ChkCastClassSpecial(void* toTypeHnd, object obj)
{
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj);
Debug.Assert(mt != toTypeHnd, "The check for the trivial cases should be inlined by the JIT");
for (; ; )
{
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
mt = mt->ParentMethodTable;
if (mt == toTypeHnd)
goto done;
if (mt == null)
break;
}
goto slowPath;
done:
return obj;
slowPath:
return ChkCast_Helper(toTypeHnd, obj);
}
[DebuggerHidden]
private static ref byte Unbox(void* toTypeHnd, object obj)
{
// This will throw NullReferenceException if obj is null.
if (RuntimeHelpers.GetMethodTable(obj) == toTypeHnd)
return ref obj.GetRawData();
return ref Unbox_Helper(toTypeHnd, obj);
}
[DebuggerHidden]
private static void ThrowIndexOutOfRangeException()
{
throw new IndexOutOfRangeException();
}
[DebuggerHidden]
private static void ThrowArrayMismatchException()
{
throw new ArrayTypeMismatchException();
}
[DebuggerHidden]
private static ref object? LdelemaRef(object?[] array, nint index, void* type)
{
// This will throw NullReferenceException if array is null.
if ((nuint)index >= (uint)array.Length)
ThrowIndexOutOfRangeException();
Debug.Assert(index >= 0);
ref object? element = ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(array), index);
void* elementType = RuntimeHelpers.GetMethodTable(array)->ElementType;
if (elementType != type)
ThrowArrayMismatchException();
return ref element;
}
[DebuggerHidden]
private static void StelemRef(object?[] array, nint index, object? obj)
{
// This will throw NullReferenceException if array is null.
if ((nuint)index >= (uint)array.Length)
ThrowIndexOutOfRangeException();
Debug.Assert(index >= 0);
ref object? element = ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(array), index);
void* elementType = RuntimeHelpers.GetMethodTable(array)->ElementType;
if (obj == null)
goto assigningNull;
if (elementType != RuntimeHelpers.GetMethodTable(obj))
goto notExactMatch;
doWrite:
WriteBarrier(ref element, obj);
return;
assigningNull:
element = null;
return;
notExactMatch:
if (array.GetType() == typeof(object[]))
goto doWrite;
StelemRef_Helper(ref element, elementType, obj);
}
[DebuggerHidden]
[MethodImpl(MethodImplOptions.NoInlining)]
private static void StelemRef_Helper(ref object? element, void* elementType, object obj)
{
CastResult result = CastCache.TryGet(s_table!, (nuint)RuntimeHelpers.GetMethodTable(obj), (nuint)elementType);
if (result == CastResult.CanCast)
{
WriteBarrier(ref element, obj);
return;
}
StelemRef_Helper_NoCacheLookup(ref element, elementType, obj);
}
[DebuggerHidden]
private static void StelemRef_Helper_NoCacheLookup(ref object? element, void* elementType, object obj)
{
Debug.Assert(obj != null);
obj = IsInstanceOfAny_NoCacheLookup(elementType, obj);
if (obj == null)
{
ThrowArrayMismatchException();
}
WriteBarrier(ref element, obj);
}
}
}
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