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Assets/Cryville/Common/Pdt/PdtOperator.cs

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+using System;
+
+namespace Cryville.Common.Pdt {
+	/// <summary>
+	/// PDT operator.
+	/// </summary>
+	public unsafe abstract class PdtOperator {
+		byte* _prmem;
+		int _loadindex;
+		readonly PdtVariableMemory[] _operands;
+		/// <summary>
+		/// The count of the operands loaded.
+		/// </summary>
+		protected int LoadedOperandCount { get { return ParamCount - _loadindex; } }
+		/// <summary>
+		/// Gets the operand at the specified index.
+		/// </summary>
+		/// <param name="index">The index.</param>
+		/// <returns>The operand at the specified index.</returns>
+		/// <exception cref="IndexOutOfRangeException"><paramref name="index" /> is not less than <see cref="LoadedOperandCount" /> or less than 0.</exception>
+		protected PdtVariableMemory GetOperand(int index) {
+			if (index >= LoadedOperandCount || index < 0) throw new IndexOutOfRangeException();
+			int i = index + _loadindex;
+			return _operands[i];
+		}
+		internal int ParamCount { get; private set; }
+		/// <summary>
+		/// Creates an instance of the <see cref="PdtOperator" /> class.
+		/// </summary>
+		/// <param name="pc">The suggested parameter count.</param>
+		protected PdtOperator(int pc) {
+			ParamCount = pc;
+			_operands = new PdtVariableMemory[pc];
+		}
+		PdtEvaluatorBase _etor;
+		bool _failure = false;
+		bool _rfreq = true;
+		internal void Begin(PdtEvaluatorBase etor) {
+			_etor = etor;
+			_failure = false;
+			_loadindex = ParamCount;
+		}
+		internal void LoadOperand(PdtVariableMemory mem) {
+			if (_loadindex == 0) return;
+			_operands[--_loadindex] = mem;
+		}
+		internal void Call(byte* prmem, bool noset) {
+			_prmem = prmem;
+			_rfreq = false;
+			Execute();
+			if (!_rfreq && !noset) throw new InvalidOperationException("Return frame not set");
+			if (_failure) {
+				if (_rfreq) _etor.DiscardStack();
+				throw new InvalidOperationException("Evaluation failed");
+			}
+		}
+		/// <summary>
+		/// Executes the operator.
+		/// </summary>
+		protected abstract void Execute();
+		/// <summary>
+		/// Gets a return frame.
+		/// </summary>
+		/// <param name="type">The type of the frame.</param>
+		/// <param name="len">The length of the frame.</param>
+		/// <returns>The return frame.</returns>
+		/// <exception cref="InvalidOperationException">The return frame has already been requested.</exception>
+		protected PdtVariableMemory GetReturnFrame(int type, int len) {
+			if (_rfreq) {
+				_failure = true;
+				throw new InvalidOperationException("Return frame already requested");
+			}
+			_rfreq = true;
+			return _etor.StackAlloc(type, _prmem, len);
+		}
+	}
+}