src/main/java/eu/svjatoslav/commons/string/tokenizer/Tokenizer.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2017, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 3 of the GNU Lesser General Public License
   7  * or later as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.commons.string.tokenizer;
  11
  12 import java.util.ArrayList;
  13 import java.util.List;
  14 import java.util.Stack;
  15
  16 import static eu.svjatoslav.commons.string.tokenizer.Terminator.TerminationStrategy.DROP;
  17
  18 public class Tokenizer {
  19
  20     final Stack<Integer> tokenIndexes = new Stack<>();
  21     private final List<Terminator> terminators = new ArrayList<>();
  22     private String source;
  23     private int currentIndex = 0;
  24
  25     public Tokenizer(final String source) {
  26         this.source = source;
  27     }
  28
  29     public Tokenizer(){}
  30
  31     public Tokenizer setSource(String source){
  32         this.source = source;
  33         currentIndex = 0;
  34         return this;
  35     }
  36
  37     public Tokenizer addTerminator(final String startSequence,
  38                                    final Terminator.TerminationStrategy terminationStrategy) {
  39         terminators.add(new Terminator(startSequence, terminationStrategy));
  40         return this;
  41     }
  42
  43     public Tokenizer addTerminator(final String startSequence,
  44                                    final String endSequence, final Terminator.TerminationStrategy terminationStrategy) {
  45         terminators.add(new Terminator(startSequence, endSequence, terminationStrategy));
  46         return this;
  47     }
  48
  49     public void expectNextToken(final String value)
  50             throws InvalidSyntaxException {
  51         final TokenizerMatch match = getNextToken();
  52         if (!value.equals(match.token))
  53             throw new InvalidSyntaxException("Expected \"" + value
  54                     + "\" but got \"" + match.token + "\" instead.");
  55     }
  56
  57     public TokenizerMatch getNextToken() {
  58         tokenIndexes.push(currentIndex);
  59         final StringBuilder result = new StringBuilder();
  60
  61         while (true) {
  62             if (currentIndex >= source.length())
  63                 return null;
  64
  65             boolean accumulateCurrentChar = true;
  66
  67             for (final Terminator terminator : terminators)
  68                 if (sequenceMatches(terminator.startSequence))
  69
  70                     if (terminator.termination == DROP) {
  71                         currentIndex += terminator.startSequence.length();
  72
  73                         if (terminator.endSequence != null)
  74                             skipUntilSequence(terminator.endSequence);
  75
  76                         if (result.length() > 0)
  77                             return new TokenizerMatch(result.toString(),
  78                                     terminator);
  79                         else {
  80                             accumulateCurrentChar = false;
  81                             break;
  82                         }
  83                     } else if (result.length() > 0)
  84                         return new TokenizerMatch(result.toString(), terminator);
  85                     else {
  86                         currentIndex += terminator.startSequence.length();
  87                         return new TokenizerMatch(terminator.startSequence,
  88                                 terminator);
  89                     }
  90
  91             if (accumulateCurrentChar) {
  92                 result.append(source.charAt(currentIndex));
  93                 currentIndex++;
  94             }
  95         }
  96
  97     }
  98
  99     public boolean consumeIfNextToken(final String token) {
 100         if (token.equals(getNextToken().token))
 101             return true;
 102
 103         unreadToken();
 104         return false;
 105     }
 106
 107     public boolean sequenceMatches(final String sequence) {
 108         if ((currentIndex + sequence.length()) > source.length())
 109             return false;
 110
 111         for (int i = 0; i < sequence.length(); i++)
 112             if (sequence.charAt(i) != source.charAt(i + currentIndex))
 113                 return false;
 114
 115         return true;
 116     }
 117
 118     public void skipUntilDataEnd() {
 119         tokenIndexes.push(currentIndex);
 120         currentIndex = source.length();
 121     }
 122
 123     public void skipUntilSequence(final String sequence) {
 124         while (currentIndex < source.length()) {
 125             if (sequenceMatches(sequence)) {
 126                 currentIndex += sequence.length();
 127                 return;
 128             }
 129
 130             currentIndex++;
 131         }
 132     }
 133
 134     public void unreadToken() {
 135         currentIndex = tokenIndexes.pop();
 136     }
 137
 138 }