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1 using Implab;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Diagnostics;
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5 using System.Linq;
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6 using System.Text;
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7 using System.Threading.Tasks;
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8
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9 namespace Implab.Parsing {
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10 public abstract class DFAutomaton<T> {
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11 protected struct ContextFrame {
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12 public DFAStateDescriptior[] states;
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13 public int current;
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14 public T info;
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15 }
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16
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17 public const int INITIAL_STATE = DFADefinitionBase.INITIAL_STATE;
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18 public const int UNREACHEBLE_STATE = DFADefinitionBase.UNREACHEBLE_STATE;
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19
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20 protected ContextFrame m_context;
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21 Stack<ContextFrame> m_contextStack = new Stack<ContextFrame>();
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22
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23 public int Level {
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24 get { return m_contextStack.Count; }
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25 }
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26
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27 protected DFAutomaton(DFAStateDescriptior[] states, int startState, T info) {
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28 Safe.ArgumentNotNull(states, "states");
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29 Safe.ArgumentInRange(startState, 0, states.Length - 1, "startState");
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30
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31 m_context.states = states;
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32 m_context.current = startState;
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33 m_context.info = info;
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34 }
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35
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36 protected void Switch(DFAStateDescriptior[] states, int current, T info) {
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37 Debug.Assert(states != null);
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38 Debug.Assert(current >= 0 && current < states.Length);
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39 m_contextStack.Push(m_context);
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40 m_context. states = states;
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41 m_context.current = current;
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42 m_context.info = info;
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43 }
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44
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45 protected void Restore() {
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46 Debug.Assert(m_contextStack.Count > 0);
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47
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48 m_context = m_contextStack.Pop();
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49 }
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50
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51 protected void Move(int input) {
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52 Debug.Assert(input > 0 && input < m_context.states[m_context.current].transitions.Length);
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53 m_context.current = m_context.states[m_context.current].transitions[input];
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54 }
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55 }
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56 }
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