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1 using Implab.Automaton;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Linq;
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5 using System.Text;
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6 using System.Threading.Tasks;
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7
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8 namespace Implab.Formats {
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9 public class InputScanner<TTag> {
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10 readonly TTag[] m_tags;
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11 readonly int m_initialState;
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12 readonly int[,] m_dfa;
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13 readonly CharMap m_alphabet;
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14 readonly bool[] m_final;
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15
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16 int m_position;
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17 int m_state;
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18
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19 public InputScanner(int[,] dfaTable, bool[] finalStates, TTag[] tags, int initialState, CharMap alphabet) {
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20 Safe.ArgumentNotNull(dfaTable, nameof(dfaTable));
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21 Safe.ArgumentNotNull(finalStates, nameof(finalStates));
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22 Safe.ArgumentNotNull(tags, nameof(tags));
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23 Safe.ArgumentNotNull(alphabet, nameof(alphabet));
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24
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25 m_dfa = dfaTable;
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26 m_final = finalStates;
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27 m_tags = tags;
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28 m_initialState = initialState;
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29 m_alphabet = alphabet;
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30 }
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31
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32 public TTag Tag {
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33 get {
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34 return m_tags[m_state];
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35 }
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36 }
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37
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38 public int Position {
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39 get {
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40 return m_position;
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41 }
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42 }
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43
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44 public bool IsFinal {
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45 get {
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46 return m_final[m_state];
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47 }
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48 }
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49
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50 public void Reset() {
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51 m_state = m_initialState;
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52 }
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53
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54 public InputScanner<TTag> Clone() {
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55 var clone = new InputScanner<TTag>(m_dfa, m_final, m_tags, m_initialState, m_alphabet);
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56 clone.m_state = m_state;
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57 clone.m_position = m_position;
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58 return clone;
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59 }
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60
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61 public bool Scan(char[] data, int offset, int length) {
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62 if (length <= 0) {
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63 m_position = offset;
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64 return false; // EOF
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65 }
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66
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67 var max = offset + length;
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68 var next = m_state;
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69
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70 while(offset < max) {
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71 next = m_dfa[next, m_alphabet.Translate(data[offset])];
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72 if (next == AutomatonConst.UNREACHABLE_STATE) {
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73 // scanner stops on the next position after last recognized symbol
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74 m_position = offset;
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75 return false;
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76 }
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77 m_state = next;
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78 offset++;
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79 }
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80 m_position = offset;
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81 return true;
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82 }
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83 }
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84 }
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