public D DoStep()
{
if (State.Equals(EndState))
{
return(State);
}
var instruction = Instructions[State][Current.Value];
if (instruction.IsEmpty())
{
throw new DataException("Empty instruction");
}
if (instruction.ChangeValue)
{
Current.Value = instruction.NewValue;
}
if (instruction.ChangeState)
{
State = instruction.NewState;
}
if (instruction.ReaderStep > 0)
{
if (Current.Next == null)
{
Data.AddAfter(Current, DefaultValue);
}
Current = Current.Next;
}
else if (instruction.ReaderStep < 0)
{
if (Current.Previous == null)
{
Data.AddBefore(Current, DefaultValue);
}
Current = Current.Previous;
}
return(State);
}
public HeapData Malloc(int size)
{
if (size == 0)
{
throw new XiVMError("Malloc space of size 0 is not supported");
}
if (Size + size > SizeLimit)
{
GarbageCollector.CollectGarbage();
if (Size + size > SizeLimit)
{
throw new XiVMError("Heap overflow");
}
}
// Best Fit
LinkedListNode <HeapData> best = null;
int bestFragmentSize = 0;
LinkedListNode <HeapData> cur = Data.First;
while (cur != null)
{
if (cur.Next != null)
{
int fragmentSize = (int)(cur.Next.Value.Offset - (cur.Value.Offset + cur.Value.Data.Length));
if (fragmentSize >= size)
{
// 可以填入
if (best == null || bestFragmentSize > fragmentSize)
{
// best fit
best = cur;
bestFragmentSize = fragmentSize;
}
}
}
cur = cur.Next;
}
HeapData ret = null;
if (best == null)
{
// 未找到内碎片，在末尾添加
ret = new HeapData(
Data.Count == 0 ? 0 : Data.Last.Value.Offset + (uint)Data.Last.Value.Data.Length,
new byte[size]);
Data.AddLast(ret);
}
else
{
// fit
ret = new HeapData(best.Value.Offset + (uint)best.Value.Data.Length,
new byte[size]);
Data.AddAfter(best, ret);
}
DataMap.Add(ret.Offset, ret);
Size += size;
if (Size > MaxSize)
{
MaxSize = size;
}
return(ret);
}
