/// <summary>
/// Creates a new garbage collector
/// </summary>
/// <param name="virtualMachine">The virtual machine</param>
public GarbageCollector(VirtualMachine virtualMachine)
{
this.virtualMachine = virtualMachine;
this.youngGeneration = new CollectorGeneration(
virtualMachine.MemoryManager,
virtualMachine.ManagedObjectReferences,
4 * 1024 * 1024);
}
/// <summary>
/// Marks the given value
/// </summary>
/// <param name="generation">The generation</param>
/// <param name="value">The value</param>
/// <param name="type">The type of the value</param>
private void MarkValue(CollectorGeneration generation, long value, BaseType type)
{
if (type.IsReference)
{
//Don't mark nulls
if (value == 0)
{
return;
}
this.MarkObject(generation, this.GetObjectReference(new IntPtr(value)));
}
}
/// <summary>
/// Sweeps the objects in the given generation
/// </summary>
/// <param name="generation">The generation</param>
private void SweepObjects(CollectorGeneration generation)
{
generation.Heap.VisitObjects(objectReference =>
{
if (objectReference.IsMarked)
{
objectReference.Unmark();
objectReference.IncreaseSurvivalCount();
}
else
{
if (this.virtualMachine.Config.EnableDebug && this.virtualMachine.Config.PrintDeallocation)
{
RuntimeInterface.DebugLog($"Deleted object {objectReference}");
}
this.DeleteObject(objectReference);
}
});
}
/// <summary>
/// Marks all the objects starting at the given frame
/// </summary>
/// <param name="generation">The generation</param>
/// <param name="stackFrame">The stack frame</param>
private void MarkAllObjects(CollectorGeneration generation, StackFrame stackFrame)
{
var stalkWalker = new StackWalker(this.virtualMachine.CallStack);
stalkWalker.VisitObjectReferences(
stackFrame,
frameEntry =>
{
var objectPointer = new IntPtr(frameEntry.Value);
this.MarkObject(generation, this.GetObjectReference(objectPointer));
},
frame =>
{
if (this.virtualMachine.Config.EnableDebug && this.virtualMachine.Config.PrintStackFrameWhenGC)
{
RuntimeInterface.DebugLog($"{frame.Function.Definition.Name} ({frame.InstructionIndex})");
RuntimeInterface.PrintStackFrame(frame, false);
}
});
}
/// <summary>
/// Allocates an object of the given size
/// </summary>
/// <param name="generation">The generation to allocate in</param>
/// <param name="type">The type of the object</param>
/// <param name="size">The size of the object</param>
private IntPtr AllocateObject(CollectorGeneration generation, BaseType type, int size)
{
var fullSize = Constants.ObjectHeaderSize + size;
var objectPointer = generation.Allocate(fullSize);
NativeHelpers.SetBlock(objectPointer, fullSize, 0);
//Set the header
var typeObjectRef = this.virtualMachine.GetManagedReference(type);
NativeHelpers.SetInt(objectPointer, 0, typeObjectRef); //Type
NativeHelpers.SetByte(objectPointer, Constants.ManagedObjectReferenceSize, 0); //GC info
var dataPointer = objectPointer + Constants.ObjectHeaderSize;
if (this.virtualMachine.Config.LogAllocation)
{
this.Allocations.Add(dataPointer);
}
//The returned ptr is to the data
return(dataPointer);
}
/// <summary>
/// Marks the given object
/// </summary>
/// <param name="generation">The generation</param>
/// <param name="objectReference">A reference to the object</param>
private void MarkObject(CollectorGeneration generation, ObjectReference objectReference)
{
if (!objectReference.IsMarked)
{
objectReference.Mark();
if (objectReference.Type.IsArray)
{
//Mark ref elements
var arrayType = (ArrayType)objectReference.Type;
if (arrayType.ElementType.IsReference)
{
var arrayReference = new ArrayReference(objectReference);
for (int i = 0; i < arrayReference.Length; i++)
{
var elementPtr = arrayReference.GetElement(i);
this.MarkValue(generation, NativeHelpers.ReadLong(elementPtr), arrayType.ElementType);
}
}
}
else if (objectReference.Type.IsClass)
{
//Mark ref fields
var classType = (ClassType)objectReference.Type;
foreach (var field in classType.Metadata.Fields)
{
if (field.Type.IsReference)
{
var fieldValue = NativeHelpers.ReadLong(objectReference.DataPointer + field.LayoutOffset);
this.MarkValue(generation, fieldValue, field.Type);
}
}
}
}
}
