|
1
22
23 package org.javacc.parser;
24
25 import java.util.Vector  ;
26
27 public class LookaheadWalk {
28
29 public static boolean considerSemanticLA;
30
31 public static Vector sizeLimitedMatches;
32
33 public static void vectorAppend(Vector vToAppendTo, Vector vToAppend) {
34 for (int i = 0; i < vToAppend.size(); i++) {
35 vToAppendTo.addElement(vToAppend.elementAt(i));
36 }
37 }
38
39 public static Vector genFirstSet(Vector partialMatches, Expansion exp) {
40 if (exp instanceof RegularExpression) {
41 Vector retval = new Vector ();
42 for (int i = 0; i < partialMatches.size(); i++) {
43 MatchInfo m = (MatchInfo)partialMatches.elementAt(i);
44 MatchInfo mnew = new MatchInfo();
45 for (int j = 0; j < m.firstFreeLoc; j++) {
46 mnew.match[j] = m.match[j];
47 }
48 mnew.firstFreeLoc = m.firstFreeLoc;
49 mnew.match[mnew.firstFreeLoc++] = ((RegularExpression)exp).ordinal;
50 if (mnew.firstFreeLoc == MatchInfo.laLimit) {
51 sizeLimitedMatches.addElement(mnew);
52 } else {
53 retval.addElement(mnew);
54 }
55 }
56 return retval;
57 } else if (exp instanceof NonTerminal) {
58 NormalProduction prod = ((NonTerminal)exp).prod;
59 if (prod instanceof JavaCodeProduction) {
60 return new Vector ();
61 } else {
62 return genFirstSet(partialMatches, prod.expansion);
63 }
64 } else if (exp instanceof Choice) {
65 Vector retval = new Vector ();
66 Choice ch = (Choice)exp;
67 for (int i = 0; i < ch.choices.size(); i++) {
68 Vector v = genFirstSet(partialMatches, (Expansion)ch.choices.elementAt(i));
69 vectorAppend(retval, v);
70 }
71 return retval;
72 } else if (exp instanceof Sequence) {
73 Vector v = partialMatches;
74 Sequence seq = (Sequence)exp;
75 for (int i = 0; i < seq.units.size(); i++) {
76 v = genFirstSet(v, (Expansion)seq.units.elementAt(i));
77 if (v.size() == 0) break;
78 }
79 return v;
80 } else if (exp instanceof OneOrMore) {
81 Vector retval = new Vector ();
82 Vector v = partialMatches;
83 OneOrMore om = (OneOrMore)exp;
84 while (true) {
85 v = genFirstSet(v, om.expansion);
86 if (v.size() == 0) break;
87 vectorAppend(retval, v);
88 }
89 return retval;
90 } else if (exp instanceof ZeroOrMore) {
91 Vector retval = new Vector ();
92 vectorAppend(retval, partialMatches);
93 Vector v = partialMatches;
94 ZeroOrMore zm = (ZeroOrMore)exp;
95 while (true) {
96 v = genFirstSet(v, zm.expansion);
97 if (v.size() == 0) break;
98 vectorAppend(retval, v);
99 }
100 return retval;
101 } else if (exp instanceof ZeroOrOne) {
102 Vector retval = new Vector ();
103 vectorAppend(retval, partialMatches);
104 vectorAppend(retval, genFirstSet(partialMatches, ((ZeroOrOne)exp).expansion));
105 return retval;
106 } else if (exp instanceof TryBlock) {
107 return genFirstSet(partialMatches, ((TryBlock)exp).exp);
108 } else if (considerSemanticLA &&
109 exp instanceof Lookahead &&
110 ((Lookahead)exp).action_tokens.size() != 0
111 ) {
112 return new Vector ();
113 } else {
114 Vector retval = new Vector ();
115 vectorAppend(retval, partialMatches);
116 return retval;
117 }
118 }
119
120 public static void vectorSplit(Vector toSplit, Vector mask, Vector partInMask, Vector rest) {
121 OuterLoop:
122 for (int i = 0; i < toSplit.size(); i++) {
123 for (int j = 0; j < mask.size(); j++) {
124 if (toSplit.elementAt(i) == mask.elementAt(j)) {
125 partInMask.addElement(toSplit.elementAt(i));
126 continue OuterLoop;
127 }
128 }
129 rest.addElement(toSplit.elementAt(i));
130 }
131 }
132
133 public static Vector genFollowSet(Vector partialMatches, Expansion exp, long generation) {
134 if (exp.myGeneration == generation) {
135 return new Vector ();
136 }
137 exp.myGeneration = generation;
139 if (exp.parent == null) {
140 Vector retval = new Vector ();
141 vectorAppend(retval, partialMatches);
142 return retval;
143 } else if (exp.parent instanceof NormalProduction) {
144 Vector parents = ((NormalProduction)exp.parent).parents;
145 Vector retval = new Vector ();
146 for (int i = 0; i < parents.size(); i++) {
148 Vector v = genFollowSet(partialMatches, (Expansion)parents.elementAt(i), generation);
149 vectorAppend(retval, v);
150 }
151 return retval;
152 } else if (exp.parent instanceof Sequence) {
153 Sequence seq = (Sequence)exp.parent;
154 Vector v = partialMatches;
155 for (int i = exp.ordinal+1; i < seq.units.size(); i++) {
156 v = genFirstSet(v, (Expansion)seq.units.elementAt(i));
157 if (v.size() == 0) return v;
158 }
159 Vector v1 = new Vector ();
160 Vector v2 = new Vector ();
161 vectorSplit(v, partialMatches, v1, v2);
162 if (v1.size() != 0) {
163 v1 = genFollowSet(v1, seq, generation);
165 }
166 if (v2.size() != 0) {
167 v2 = genFollowSet(v2, seq, Expansion.nextGenerationIndex++);
169 }
170 vectorAppend(v2, v1);
171 return v2;
172 } else if (exp.parent instanceof OneOrMore || exp.parent instanceof ZeroOrMore) {
173 Vector moreMatches = new Vector ();
174 vectorAppend(moreMatches, partialMatches);
175 Vector v = partialMatches;
176 while (true) {
177 v = genFirstSet(v, exp);
178 if (v.size() == 0) break;
179 vectorAppend(moreMatches, v);
180 }
181 Vector v1 = new Vector ();
182 Vector v2 = new Vector ();
183 vectorSplit(moreMatches, partialMatches, v1, v2);
184 if (v1.size() != 0) {
185 v1 = genFollowSet(v1, (Expansion)exp.parent, generation);
187 }
188 if (v2.size() != 0) {
189 v2 = genFollowSet(v2, (Expansion)exp.parent, Expansion.nextGenerationIndex++);
191 }
192 vectorAppend(v2, v1);
193 return v2;
194 } else {
195 return genFollowSet(partialMatches, (Expansion)exp.parent, generation);
197 }
198 }
199
200 public static void reInit()
201 {
202 considerSemanticLA = false;
203 sizeLimitedMatches = null;
204 }
205
206 }
207 |
Popular Tags |
Java API By Example, From Geeks To Geeks.